As an important river in the central part of Jilin Province, the Yinma River plays a crucial role in the daily lives of the people in Jilin Province. In this paper, 15 cross sections were selected in the Yinma River b...As an important river in the central part of Jilin Province, the Yinma River plays a crucial role in the daily lives of the people in Jilin Province. In this paper, 15 cross sections were selected in the Yinma River basin. Based on the water quality monitoring data from 2012 to 2021, referring to the Environmental Quality Standards for Surface Water (GB 3838-2002) and historical monitoring data of the river, dissolved oxygen (DO), five-day biochemical oxygen demand (BOD 5), permanganate index (COD Mn ), chemical oxygen demand (COD), ammonia nitrogen (NH 4-N), total phosphorus (TP), and total nitrogen (TN) were determined as 7 evaluation indicators, and the water quality of 15 cross sections in the Yinma River basin was comprehensively evaluated. A characteristic analysis was conducted on the water quality of the Yinma River, and its pollution sources were identified. Based on the conclusions, constructive control measures were proposed.展开更多
[Objective] The research aimed to study the variation characteristics of temperature and precipitation in Benxi area under the background of climate warming.[Method] Based on the monthly mean temperature and precipita...[Objective] The research aimed to study the variation characteristics of temperature and precipitation in Benxi area under the background of climate warming.[Method] Based on the monthly mean temperature and precipitation data of four routine meteorological stations in Benxi area from 1953 to 2010,by using linear tendency rate,linear regression equation,wavelet analysis,Mann-Kendall detection and so on,the variation characteristics of temperature and precipitation under the background of climate warming in the area were analyzed.[Result] The annual average temperature during 1953-2010 in Benxi area presented rise trend,and the linear tendency rate was 0.28 ℃/10 a.It was temperature increase trend in four seasons.The temperature rise rate in winter was the maximum and was the minimum in summer.The annual rainfall presented decrease trend,and the linear tendency rate was-18.16 mm/10 a.Except in spring,it was decrease trend in other seasons.Mann-Kendall mutation detection showed that the mutation of annual average temperature in Benxi area in recent 58 years appeared in 1986.There was no mutation phenomenon in summer.Spring mutation appeared in 1974,and autumn mutation appeared in 1987.Winter mutation was in 1981.The annual and seasonal precipitation didn't have the mutation phenomenon.The wavelet analysis found that the annual average temperature had the periodic variations of 12-14,5-6 and 2 years in Benxi area in recent 58 years.The annual rainfall had the periodic fluctuations of 8-12,5-6 and 2 years.[Conclusion] The research provided the scientific basis for exploration and sustainable development of the climate resources in the mountain area.展开更多
The Bohai Sea is one of the southernmost areas for sea ice formation in the northern hemisphere.Sea ice disasters in this body of water severely affect marine activities and the safety of coastal residents.In this stu...The Bohai Sea is one of the southernmost areas for sea ice formation in the northern hemisphere.Sea ice disasters in this body of water severely affect marine activities and the safety of coastal residents.In this study,we analyze the variation characteristics of the sea ice in the Bohai Sea and establish an annual regression model based on predictable mode analysis method.The results show the following:1)From 1970 to 2018,the average ice grade is(2.6±0.8),with a maximum of 4.5 and a minimum of 1.0.Liaodong Bay(LDB)has the heaviest ice conditions in the Bohai Sea,followed by Bohai Bay(BHB)and Laizhou Bay(LZB).Interannual variation is obvious in all three bays,but the linear decreasing trend is significant only in BHB.2)Three modes are obtained from empirical orthogonal function analysis,namely,single polarity mode with the same sign of anomaly in all of the three bays and strong interannual variability(82.0%),the north–south dipole mode with BHB and LZB showing an opposite sign of anomalies to that in LDB and strong decadal variations(14.5%),and a linear trend mode(3.5%).Critical factors are analyzed and regression equations are established for all the principal components,and then an annual hindcast model is established by synthesizing the results of the three modes.This model provides an annual spatial prediction of the sea ice in the Bohai Sea for the first time,and meets the demand of operational sea ice forecasting.展开更多
[Objective] The aim was to study the dynamic variation characteristics of phosphorus in paddy field runoff in saline land and its potential environmental effect. [Method] Taking Qianguo irrigation district in soda-sal...[Objective] The aim was to study the dynamic variation characteristics of phosphorus in paddy field runoff in saline land and its potential environmental effect. [Method] Taking Qianguo irrigation district in soda-saline land in Songnen Plain as study object, the dynamic variation law of phosphorus in paddy field runoff under different irrigation conditions and its potential environmental effect were discussed. [Result] Surface water in paddy field was alkaline, and scattered soil had poor fertilizer conservation capacity. Phosphorus accumulated in soil surface, which could increase the risk of phosphorus loss. Phosphorus loss in paddy field mainly occurred in irrigation period and runoff period caused by rainstorm. The concentration of total phosphorus (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP) and dissolved reactive phosphorus (DRP) in paddy field runoff decreased with time, especially PP. Phosphorus concentration exceeded critical value and resulted to eutrophication, which threatened the water quality security of Chagan Lake. Phosphorus concentration in water recession canal increased with time, and eutrophication with different degrees appeared under high temperature. TP concentration in surface water of paddy field was highly negatively correlated with that in water recession canal, and the correlation coefficients R2(α=0.05)in three paddy fields were 0.850 9, 0.896 4 and 0.915 3, respectively. The pollution load of phosphorus in paddy field with the best irrigation condition was higher, and its pollution risk was the highest. Thus, such fields should be monitored and controlled mainly as the critical source area of phosphorus loss. [Conclusion] The study could provide theoretical foundations for developing saline land rationally, establishing optimal management measure of phosphorus in saline land and controlling phosphorus loss from farmland to protect local water resources.展开更多
[Objective] The research aimed to analyze the variation characteristics of sunshine hours in Puyang City in recent 51 years.[Method] Based on the monthly sunshine hours in five meteorological stations of Puyang City d...[Objective] The research aimed to analyze the variation characteristics of sunshine hours in Puyang City in recent 51 years.[Method] Based on the monthly sunshine hours in five meteorological stations of Puyang City during 1960-2010,the annual,seasonal and monthly variation trends of sunshine hours,mutation time node were analyzed by using the climate trend coefficient,climate tendency rate,sliding average method,SNR and so on.The objective fact and rule of sunshine variation in Puyang in recent 51 years were revealed.[Result] The annual sunshine hours presented the decline trend in Puyang City in recent 51 years,and the decline range was-14.30 h/a.The seasonal sunshine hours presented the decline trend over the years,and the decline range was during-0.66 and-1.89 h/a.The maximum decline range was-1.89 h/a in summer.The monthly sunshine hours presented the decline trend over the years,and the decline range was during-21.51 and-2.13 h/a.The maximum decline range was-21.51 h/a in July.The annual sunshine hours had one mutation in 1983.The sunshine hours was more in the 1960s and 1970s.In the middle and late periods of 1980s,the sunshine hours was relatively less.[Conclusion] The research provided the guidance value for the adjustment of plantation structure and the transformation of agricultural developed manner in Puyang City.展开更多
[Objective]The research aimed to study variation characteristics of large-scale frost in the east region of the Yellow River of Gansu in recent 40 years.[Method]Based on daily minimum temperature data at 15 meteorolog...[Objective]The research aimed to study variation characteristics of large-scale frost in the east region of the Yellow River of Gansu in recent 40 years.[Method]Based on daily minimum temperature data at 15 meteorological stations over the east region of the Yellow River of Gansu from 1969 to 2008,according to common climatic statistical index of the frost,variation characteristics of the large-scale frost and continuous frost in the east region of the Yellow River of Gansu in recent 40 years were studied.[Result]Since the 1990s,average last frost date in the east region of the Yellow River of Gansu obviously advanced,and first frost date started to obviously postpone.Advancing time of the last frost date was longer than postponing time of the first frost date.Average frost-free period also obviously prolonged.Extremely early first frost date and extremely late last frost date mainly happened in the 1970s and the 1980s.Extremely late first frost date and extremely early last frost date mainly happened after the middle period of the 1990s.Extremely long frost-free period gradually started to appear frequently.In recent 40 years,the continuous frost gradually decreased,and the intensity also declined.[Conclusion]The research was favorable for understanding change characteristics of the frost and climate in the east region of the Yellow River of Gansu,and had important guidance significance for improving prediction capability of the abnormal frost disaster,effectively preventing frost disaster and improving crop yield in the area.展开更多
The geographical condition of Qingdao, China is relatively special;the transport of various inland pollutants, the emissions of marine aerosol and local pollutants will have an impact on the changes of atmospheric aer...The geographical condition of Qingdao, China is relatively special;the transport of various inland pollutants, the emissions of marine aerosol and local pollutants will have an impact on the changes of atmospheric aerosol concentration. By using the stability classification method, trajectory clustering analysis and the NOAA HYSPLIT model, the seasonal distribution characteristics of atmospheric inhalable particulate matter concentration in Qingdao, China and its relationship with meteorological conditions, mixed layer height, and the seasonal characteristics of Qingdao pollutant transport were analyzed. The results show that the variation trends of PM2.5 and PM10 were about the same, and there are obvious seasonal differences, which are high in winter and spring, and low in summer and autumn. The concentration of inhalable particulate matter has a negative correlation with temperature, wind speed and relative humidity. The concentration of inhalable particulate matter is distinct in different relative humidity ranges. When the wind speed is less than 3 - 4 m/s, there are more inhalable particles, while the mass concentration shows obvious reduction with the wind speed more than 4 m/s. There is a significant negative correlation between the mass concentration of pollutants and the daily maximum mixed layer height. The larger the concentration of pollutants, the smaller the thickness of the daily largest mixed layer. Conversely, the smaller the mass concentration of pollutants, the larger the thickness of the daily largest mixed layer. The pollutant transport in Qingdao has obvious seasonal characteristics. The air mass in spring, autumn and winter is mainly medium-long distance transport from Mongolia and southern Russia, and medium-short distance transport from Inner Mongolia and northeast of China. The source of air masses in summer is mainly transported from the eastern and sea areas.展开更多
[Objective] The research aimed to study variation characteristics of sunshine hours over Loess Plateau of Shaanxi during 1961-2010.[Method] By using the climate tendency rate,climate trend coefficient and linear corre...[Objective] The research aimed to study variation characteristics of sunshine hours over Loess Plateau of Shaanxi during 1961-2010.[Method] By using the climate tendency rate,climate trend coefficient and linear correlation,the temporal and spatial variation characteristics of sunshine hours in Loess Plateau of Shaanxi in recent 50 years were analyzed.Moreover,the main reason for inducing variation of sunshine hours in the zone was discussed.[Result] In recent 50 years,the variation of annual sunshine hours in Loess Plateau of Shaanxi mainly presented decrease trend.The decrease zones were mainly located in windy desert region along the Great Wall line,central loess hilly region,most areas of plateau remains region and most areas of arid plateau region in north Weihe River.The increase zones were mainly located in west and northeast plateau remains region,southwest plateau remains region,some areas of arid plateau region in north Weihe River.Seen from four-season variation trend,except in spring,the sunshine hours in other seasons presented varying decrease trends.The decrease amplitude in summer was 24.34 h/10 a,and was the most significant.The second one was-16.62 h/10 a in winter.The decrease amplitude in winter was 3.55 h/10 a,and was unobvious.Seen from spatial variation,the annual sunshine hours presented significant increase trend in Mizhi of loess hilly region and significant decrease trend in Dingbian,Shenmu of windy desert region along the Great Wall line,Qingjian,Yanchuan of plateau remains region,Longxian,Fengxiang,Chunhua and Hancheng of arid plateau region in north Weihe River.There was no obvious variation trend in other research zones.The annual and four-season sunshine hours all presented negative correlations with rainfall,relative humidity,total cloud amount,low cloud amount,water vapor pressure and fog days.The sunshine hours presented positive correlation with visibility.The correlation coefficients between sunshine hours and relative humidity,rainfall,total cloud amount,water vapor pressure,fog days and visibility were all bigger in each region.[Conclusion] The research provided basis for analyzing climate variation over Loess Plateau of Shaanxi.展开更多
[Objective] The research aimed to study the variation characteristics of winter temperature in Jinan in recent 60 years.[Method] Based on winter monthly average,maximum and minimum temperatures in the ground observati...[Objective] The research aimed to study the variation characteristics of winter temperature in Jinan in recent 60 years.[Method] Based on winter monthly average,maximum and minimum temperatures in the ground observation station of Jinan during 1951-2010,by using linear trend,5-year moving average and anomaly,the variation characteristics of winter average,maximum and minimum temperatures in Jinan in recent 60 years were analyzed.The historical evolution trend and decadal variation characteristics were discussed.[Result] Winter average,maximum and minimum temperatures in Jinan in recent 60 years all presented slow fluctuation rise trend.The rise trend was obvious.Especially the increase amplitude of minimum temperature was the maximum.It illustrated that the variation of minimum temperature was more sensitive than that of maximum temperature,and the climatic warming in winter was mainly from the contribution of minimum temperature rise.Seen from the decadal variation,cold winter mainly appeared before the 1970s.Then,it presented obvious decrease trend.Conversely,warm winter presented increase trend after the 1970s.Warm winter phenomenon slowed after 2000.Winter temperature presented stepped warming trend during 1950s-1990s.Winter average temperature presented jumped warming trend when entered into the 1990s.The temperature presented downward trend when entered into the 21st century.But winter temperature still presented rise trend as a whole.The population growth in Jinan made that urbanization process accelerated,and urban heat island effect aggravated.It was one of important factors for climate warming in Jinan.[Conclusion] The research provided theoretical basis for understanding the long-term variation trend of climate in Jinan area,and if it was consistent with the background of global climatic warming.展开更多
[Objective] The research aimed to study the variation characteristics of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years.[Method] Based on the daily average temperature data...[Objective] The research aimed to study the variation characteristics of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years.[Method] Based on the daily average temperature data from 1961 to 2010 at 88 meteorological stations in Guangxi,yearly days and end date of low temperature and rainy weather during spring sowing period were carried out statistics.The variation characteristics of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years were analyzed by using linear tendency calculation,phased analysis,Morlet wavelet analysis and correlation analysis.Moreover,the influences of climate warming on days and end date of low temperature and rainy weather in spring sowing period were analyzed.[Result] The average days of low temperature and rainy weather in Guangxi during spring sowing period from 1961 to 2010 was during 3.5-23.2 d.The regional distribution characteristics were that it was more in northeast and mountain zone,and less in southwest and valley.The regional distribution characteristics of end date were that it was late in northeast and mountain zone,and early in southwest and valley.The days of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years presented slight decrease trend,and the end date presented slight advancing trend.The phased variation characteristics of days and end date of low temperature and rainy weather were obvious.The days of low temperature and rainy weather from the early 1980s to metaphase of 1990s was obviously more,and the end date was obviously later.After the 1990s,the days of low temperature and rainy weather was obviously less,and the end date was obviously earlier.The days of low temperature and rainy weather had periodic oscillation signals of 4,6,8,10-14 years.The end date had periodic oscillation signals of 6,12-14 years.The days and end date of low temperature and rainy weather in Guangxi during spring sowing period significantly related to average temperature from middle dekad of February to first dekad of April.The climate warming made that the days of low temperature and rainy weather tended to decrease,and the end date tended to advance.[Conclusion] The research provided reference for further understanding the occurrence rule of low temperature and rainy weather,going after profits and avoiding disadvantages,reasonably arranging production,carrying out correlated research.展开更多
[Objective] The aim was to study the variation characteristics of longest continuous rainfall days in Shenyang in recent 48 years. [Method] Based on the data of longest continuous rainfall days in Shenyang from May to...[Objective] The aim was to study the variation characteristics of longest continuous rainfall days in Shenyang in recent 48 years. [Method] Based on the data of longest continuous rainfall days in Shenyang from May to September in 1961-2008, the variation characteristics of longest continuous rainfall days in Shenyang in recent 48 years was analyzed by means of one-dimensional linear trend estimation and wavelet analysis method. [Result] In recent 48 years, the longest continuous rainfall days in Shenyang showed decrease trend from May to September except for June in which it showed increased; the total longest continuous rainfall days showed decrease trend, and the maximum value appeared in 1986, while the minimum value could be found in 1997; from periodic variation, the total longest continuous rainfall days had the period of 2-3 years, and there also existed the period of 5-7 years after 1980; the total longest continuous rainfall days were more from the beginning of 1960s to the middle of 1990s and less thereafter. [Conclusion] The study could provide theoretical foundation for the deep research on climate change in Shenyang.展开更多
[Objective] The research aimed to study the variability and variation characteristics of climate in northern winter wheat zone during 1961-2004.[Method] Based on the meteorological data (temperature,precipitation and ...[Objective] The research aimed to study the variability and variation characteristics of climate in northern winter wheat zone during 1961-2004.[Method] Based on the meteorological data (temperature,precipitation and sunshine) of 55 meteorological stations in northern winter wheat zone during 1961-2004 and the yield data of winter wheat,by using the linear regression,correlated coefficient and climatic tendency rate,the spatial and temporal evolution characteristics of agricultural climatic resources (sunshine hours,temperature and precipitation) in northern winter wheat zone were analyzed.[Result] The annual average temperature,precipitation and sunshine hours in northern winter wheat zone during 1961-2004 all presented certain zonal distribution in the space.The precipitation and temperature gradually decreased from south to north.The sunshine hours gradually increased from south to north.The annual average temperature overall presented rise trend in northern winter wheat zone in 44 years,but the rise rate had difference in the different areas.The rise of annual average temperature in the high-latitude zone was more obvious than that in the low-latitude zone.The annual rainfall overall presented decrease trend,and the tendency rate of annual precipitation had significant difference in the different areas.The decrease rates of rainfalls in the central and western areas were bigger than that in other areas.The annual sunshine hours overall presented decline trend.In most areas,the tendency rate of annual sunshine hours was negative.But there was certain difference in the different areas.The zones where the decrease amplitude was smaller scattered in the west,and included central Shaanxi,south of Shanxi and some areas in southeast of Shandong.The decrease amplitudes were bigger in south of Henan,northwest of Shandong and south of Hebei.[Conclusion] The research provided theoretical basis for understanding the historical evolution of climate in northern winter wheat zone.展开更多
Based on the well water level data in Majiagou Mine in Tangshan City since 2000,it is suggested that the water level rise from 2008-2014 is possibly associated with reduced infiltration caused by less precipitation,to...Based on the well water level data in Majiagou Mine in Tangshan City since 2000,it is suggested that the water level rise from 2008-2014 is possibly associated with reduced infiltration caused by less precipitation,together with the effect of less groundwater exploitation. However,the water level rise from 1992-1998 cannot be interpreted properly if we extend the data source back to 1991. After comparing the data with long-term water level data of five wells with different hydro-geological units in Tangshan and Qinhuangdao, the study indicates that the long-term water level variation cannot be only attributed to the effect of less precipitation and the control of groundwater exploitation,but also with the influence of regional stress field change.With the support of regional geological and tectonic information,combined with the comprehensive analysis of CBM data obtained from the coal field,new understandings of the dynamic characteristics of annual variation are obtained.展开更多
Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline d...Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline development. In most existing studies, remote sensing images are used to quantify the morphological characteristics of lakes. However, the extraction accuracy of lake water is greatly affected by cloud cover and vegetation cover, and the inversion accuracy of lake elevation data is poor, which cannot accurately describe the response relationship of lake landscape morphology with water level change. Therefore, this paper takes Tonle Sap Lake as the research object, which is the largest natural freshwater lake in Southeast Asia. DEM is constructed based on high-resolution measured topographic data, and morphological indicators such as lake area, lake shoreline length, perimeter area ratio, longest axis length, maximum width, shoreline development index, lake shape complexity, compactness ratio and form ratio are adopted to researching the evolution law of high water overflows and low water outbursts quantitatively, and clarifying the variation characteristics of landscape morphology with water level gradient in Tonle Sap Lake. The research results have important theoretical significance for the scientific utilization of Tonle Sap Lake water resources and the protection of the lake ecosystem.展开更多
A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near th...A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle.The variation characteristics of fine particle matter(PM_(2.5)) and its components in diesel vehicle exhaust plumes were analyzed.The PM_(2.5) emissions gradually increased with increasing distance from the nozzle in the plume.Elemental carbon emissions remained basically unchanged, organic carbon and total carbon(TC) increased with increasing distance.The concentrations of SO_(4)^(2-),NO_(3)^(-) and NH_(4)^(+) (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume.The selective catalytic reduction(SCR) reduced 42.7% TC, 40% NO_(3)^(-) emissions, but increased 104% SO_(4)^(2-) and 36% NH_(4)^(+) emissions, respectively.In summary,the SCR reduced 29% primary PM_(2.5) emissions for the tested diesel vehicles.The NH_(4)NO_(3) particle formation maybe more important in the plume, and there maybe other forms of formation of NH_(4)^(+) (eg.NH4Cl).The generation of secondary organic carbon(SOC) plays a leading role in the generation of secondary PM_(2.5).The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process.The inconsistency between secondary organic aerosol(SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.展开更多
[Objective] The aim was to study the characteristics of sunshine hour changes in Tacheng in recent 50 years.[Method] By dint of the measured data of annual,seasonal and monthly sunshine hour's changes in four mete...[Objective] The aim was to study the characteristics of sunshine hour changes in Tacheng in recent 50 years.[Method] By dint of the measured data of annual,seasonal and monthly sunshine hour's changes in four meteorological observatories from 1960 to 2009,using linear regression analysis method,the characteristics of sunshine hour changes in Tacheng in recent 50 years were studied.[Result] The results showed that the annual average sunshine hours in Tacheng Basin in recent 50 years were above 2 800.0 h,among which Tacheng,Yumin had the most,2 936.1,2 921.3 h respectively and Emin the least,2 814.2 h.The sunshine hours were the most in autumn and summer,followed by winter,and were least in spring;sunshine hours during growth season in Tacheng and Yumin were the most,followed by Emin and then Tuoli.The linear tendency rate of sunshine hours in four stations in February was negative.But only the value in Tacheng,Emin decreased at a rate of-4.7 and-6.0 respectively;the linear tendency rate of sunshine hours in four stations in May,June and October were positive,but only Yumin station mounted at a rate of 14.5,12.6,11.2 h/10 a.The linear tendency of seasonal sunshine hours during the year and the growth season increased in Yumin at a rate of 74.9 and 60.5 h/10 a.The linear tendency rate of sunshine hours in four stations in winter was negative,among which the rate of Tacheng,Emin and Tuoli decreased at a rate of-5.5,-6.7,-4.9 h/10 a;that in other three seasons,only in Yumin,it increased most rapidly at a rate of 9.7,7.7 and 7.0 h/10 a.[Conclusion] The study provides theoretical reference for the adjustment and perfection of husbandry industry structure and optimization,reasonable development and utilization of solar energy resources.展开更多
On July 29, 2021, a large earthquake of MW8.2 occurred south of the Alaska Peninsula. To investigate the spatial-temporal changes of crustal stress in the earthquake-stricken area before this event, we selected 159 ea...On July 29, 2021, a large earthquake of MW8.2 occurred south of the Alaska Peninsula. To investigate the spatial-temporal changes of crustal stress in the earthquake-stricken area before this event, we selected 159 earthquakes of 4.7 ≤ MW ≤ 6.9 that occurred in the epicentral region and its surroundings between January 1980 and June 2021 to study the temporal variation and spatial distribution of their apparent stress. In addition, we analyzed the correlation between seismic activities and Earth’s rotation and explored the seismogenic process of this earthquake. The crustal stress rose from January 2008 to December 2016. This period was followed by a sub-instability stage from January 2017 until the occurrence of the MW8.2 earthquake. The average rate of apparent stress change in the first five years of the stress increase period was roughly 2.3 times that in the last four years. The lateral distribution of the apparent stress shows that the areas with apparent stress greater than 1.0 MPa exhibited an expanding trend during the seismogenic process. The maximum apparent stress was located at the earthquake epicenter during the last four years. The distribution of the apparent stress in the E-W vertical cross section revealed that an apparent stress gap formed around the hypocenter during the first five years of the stress increase period, surrounded by areas of relatively high apparent stress. After the Alaska earthquake, most parts of this gap were filled in by aftershocks. The seismic activities during the sub-instability stage exhibited a significant correlation with Earth’s rotation.展开更多
Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year(1961-2005) and 86-station observational precipitation data of Guangdong,and the causes of drought events are disc...Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year(1961-2005) and 86-station observational precipitation data of Guangdong,and the causes of drought events are discussed from different angles(e.g.,atmospheric circulation,sea surface temperature) on the basis of global coverage datasets of sea surface temperature and atmospheric elements.It is found that the occurrence frequency of persistent drought events in Guangdong province is once every 26 months on average,and autumn-winter or winter-spring persistent drought events take up the majority.The persistent drought events possess large scale spatial characteristics.While the 1960s is the most frequent and strongest decade of drought events in the latter half of the 20th century,the occurrence is more frequent and the intensity is stronger in the first five years of the 21st century(2001-2005).This reflects the response of regional extreme climatic events in Guangdong to global climatic change.The atmospheric circulation,sea surface temperature,etc,appear to have different abnormal characteristics when drought events happen in different seasons.The results of this paper provide some good reference information for the drought forecast,especially for the dynamic interpretation of climatic model products.展开更多
[Objective] The research aimed to analyze temporal and spatial variation characteristics of temperature in Shangqiu City during 1961-2010.[Method] Based on temperature data in eight meteorological stations of Shangqiu...[Objective] The research aimed to analyze temporal and spatial variation characteristics of temperature in Shangqiu City during 1961-2010.[Method] Based on temperature data in eight meteorological stations of Shangqiu during 1961-2010,by using trend analysis method,the temporal and spatial evolution characteristics of annual average temperature,annual average maximum and minimum temperatures,annual extreme maximum and minimum temperatures,daily range of annual average temperature in Shangqiu City were analyzed.M-K method was used to determine mutation year of temperature.[Result] The annual average temperature,annual average minimum temperature and annual extreme minimum temperature respectively rose at 0.122,0.255 and 0.488 ℃/10 a.The variation trend of annual average maximum temperature wasn't obvious.The daily range of annual average temperature and annual extreme maximum temperature respectively declined at-0.217 and-0.292 ℃/10 a.Seen from spatial distribution,the increase amplitudes of annual average temperature,annual average minimum temperature and annual extreme minimum temperature were all large in the east and small in the west.The decrease amplitude of daily range of annual average temperature was large in the east and small in the west.The decrease amplitude of annual extreme maximum temperature was large in the west and small in the east.The annual average maximum temperature had trends of increase and decrease.The annual average temperature,annual average minimum temperature and daily range of annual average temperature all mutated in 1997.The annual average maximum temperature didn't have obvious mutation point.The annual extreme maximum temperature mutated in 1973.The annual extreme minimum temperature respectively mutated in 1989 and 1999.[Conclusion] The research played important guidance significances in adjustment of agricultural production structure,regional climate planning,reasonably using climate resource and replying climate change in Shangqiu City.展开更多
[Objective] The research aimed to study the variation rule of precipitation in the rainy season in Liupanshui City in recent 50 years. [Method] Based on the monthly precipitation data from three observatories (Liuzhi,...[Objective] The research aimed to study the variation rule of precipitation in the rainy season in Liupanshui City in recent 50 years. [Method] Based on the monthly precipitation data from three observatories (Liuzhi, Panxian and Shuicheng) of Liupanshui City from May to September during 1960-2009, the interannual, interdecadal variation and mutation characteristics of precipitation in the rainy season in Liupanshui City in recent 50 years were analyzed by using the linear tendency estimation, sliding T-test and Morlet wavelet analysis method. [Result] The rainfall in the rainy season in Liupanshui City in recent 50 years presented the decline trend, and the linear tendency rate was -15.4 mm/10 a. The precipitation in the rainy season in Liupanshui City had the obvious interannual and interdecadal variation characteristics. It was the obvious rainless period in the metaphase of 1960s, and the precipitation was comparatively more in late 1960s. It was the relatively rainless period in the whole 1970s. From late 1970s to late 1980s, the precipitation in the rainy season entered into the pluvial period, and it was the period when the precipitation was the most in recent 50 years. The precipitation was relatively less from late 1980s to metaphase of 1990s. It was the pluvial period in the middle and late periods of 1990s, and it was the rainless period when entered into the 21st century. The sliding T-test showed that the precipitation mutation point in the rainy season in Liupanshui City in recent 50 years was in 2002. The wavelet analysis showed that the precipitation in the rainy season in Liupanshui City had the significant multiple time scale characteristic. In the interdecadal scale, the precipitation had the significant 16-year periodic oscillation which stably existed in 50 years. In the interannual scale, the precipitation had the quasi-8-year periodic oscillation. [Conclusion] The research provided the scientific basis for the accurate forecast of drought and flood disasters, disaster prevention and reduction in the city.展开更多
文摘As an important river in the central part of Jilin Province, the Yinma River plays a crucial role in the daily lives of the people in Jilin Province. In this paper, 15 cross sections were selected in the Yinma River basin. Based on the water quality monitoring data from 2012 to 2021, referring to the Environmental Quality Standards for Surface Water (GB 3838-2002) and historical monitoring data of the river, dissolved oxygen (DO), five-day biochemical oxygen demand (BOD 5), permanganate index (COD Mn ), chemical oxygen demand (COD), ammonia nitrogen (NH 4-N), total phosphorus (TP), and total nitrogen (TN) were determined as 7 evaluation indicators, and the water quality of 15 cross sections in the Yinma River basin was comprehensively evaluated. A characteristic analysis was conducted on the water quality of the Yinma River, and its pollution sources were identified. Based on the conclusions, constructive control measures were proposed.
文摘[Objective] The research aimed to study the variation characteristics of temperature and precipitation in Benxi area under the background of climate warming.[Method] Based on the monthly mean temperature and precipitation data of four routine meteorological stations in Benxi area from 1953 to 2010,by using linear tendency rate,linear regression equation,wavelet analysis,Mann-Kendall detection and so on,the variation characteristics of temperature and precipitation under the background of climate warming in the area were analyzed.[Result] The annual average temperature during 1953-2010 in Benxi area presented rise trend,and the linear tendency rate was 0.28 ℃/10 a.It was temperature increase trend in four seasons.The temperature rise rate in winter was the maximum and was the minimum in summer.The annual rainfall presented decrease trend,and the linear tendency rate was-18.16 mm/10 a.Except in spring,it was decrease trend in other seasons.Mann-Kendall mutation detection showed that the mutation of annual average temperature in Benxi area in recent 58 years appeared in 1986.There was no mutation phenomenon in summer.Spring mutation appeared in 1974,and autumn mutation appeared in 1987.Winter mutation was in 1981.The annual and seasonal precipitation didn't have the mutation phenomenon.The wavelet analysis found that the annual average temperature had the periodic variations of 12-14,5-6 and 2 years in Benxi area in recent 58 years.The annual rainfall had the periodic fluctuations of 8-12,5-6 and 2 years.[Conclusion] The research provided the scientific basis for exploration and sustainable development of the climate resources in the mountain area.
基金supported by the National Natural Science Foundation of China(Nos.U1706216 and 41575067)the National Key Research and Development Program(Nos.2015CB953904,2016YFC1402000,and 2016YFC 1401500)
文摘The Bohai Sea is one of the southernmost areas for sea ice formation in the northern hemisphere.Sea ice disasters in this body of water severely affect marine activities and the safety of coastal residents.In this study,we analyze the variation characteristics of the sea ice in the Bohai Sea and establish an annual regression model based on predictable mode analysis method.The results show the following:1)From 1970 to 2018,the average ice grade is(2.6±0.8),with a maximum of 4.5 and a minimum of 1.0.Liaodong Bay(LDB)has the heaviest ice conditions in the Bohai Sea,followed by Bohai Bay(BHB)and Laizhou Bay(LZB).Interannual variation is obvious in all three bays,but the linear decreasing trend is significant only in BHB.2)Three modes are obtained from empirical orthogonal function analysis,namely,single polarity mode with the same sign of anomaly in all of the three bays and strong interannual variability(82.0%),the north–south dipole mode with BHB and LZB showing an opposite sign of anomalies to that in LDB and strong decadal variations(14.5%),and a linear trend mode(3.5%).Critical factors are analyzed and regression equations are established for all the principal components,and then an annual hindcast model is established by synthesizing the results of the three modes.This model provides an annual spatial prediction of the sea ice in the Bohai Sea for the first time,and meets the demand of operational sea ice forecasting.
基金Supported by National Water Pollution Control and Management Science & Technology Specific Projects of China(2008ZX07207-006-04)Innovation Foundation Projects for Doctoral Students of Donghua University in 2011(11D11311)
文摘[Objective] The aim was to study the dynamic variation characteristics of phosphorus in paddy field runoff in saline land and its potential environmental effect. [Method] Taking Qianguo irrigation district in soda-saline land in Songnen Plain as study object, the dynamic variation law of phosphorus in paddy field runoff under different irrigation conditions and its potential environmental effect were discussed. [Result] Surface water in paddy field was alkaline, and scattered soil had poor fertilizer conservation capacity. Phosphorus accumulated in soil surface, which could increase the risk of phosphorus loss. Phosphorus loss in paddy field mainly occurred in irrigation period and runoff period caused by rainstorm. The concentration of total phosphorus (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP) and dissolved reactive phosphorus (DRP) in paddy field runoff decreased with time, especially PP. Phosphorus concentration exceeded critical value and resulted to eutrophication, which threatened the water quality security of Chagan Lake. Phosphorus concentration in water recession canal increased with time, and eutrophication with different degrees appeared under high temperature. TP concentration in surface water of paddy field was highly negatively correlated with that in water recession canal, and the correlation coefficients R2(α=0.05)in three paddy fields were 0.850 9, 0.896 4 and 0.915 3, respectively. The pollution load of phosphorus in paddy field with the best irrigation condition was higher, and its pollution risk was the highest. Thus, such fields should be monitored and controlled mainly as the critical source area of phosphorus loss. [Conclusion] The study could provide theoretical foundations for developing saline land rationally, establishing optimal management measure of phosphorus in saline land and controlling phosphorus loss from farmland to protect local water resources.
文摘[Objective] The research aimed to analyze the variation characteristics of sunshine hours in Puyang City in recent 51 years.[Method] Based on the monthly sunshine hours in five meteorological stations of Puyang City during 1960-2010,the annual,seasonal and monthly variation trends of sunshine hours,mutation time node were analyzed by using the climate trend coefficient,climate tendency rate,sliding average method,SNR and so on.The objective fact and rule of sunshine variation in Puyang in recent 51 years were revealed.[Result] The annual sunshine hours presented the decline trend in Puyang City in recent 51 years,and the decline range was-14.30 h/a.The seasonal sunshine hours presented the decline trend over the years,and the decline range was during-0.66 and-1.89 h/a.The maximum decline range was-1.89 h/a in summer.The monthly sunshine hours presented the decline trend over the years,and the decline range was during-21.51 and-2.13 h/a.The maximum decline range was-21.51 h/a in July.The annual sunshine hours had one mutation in 1983.The sunshine hours was more in the 1960s and 1970s.In the middle and late periods of 1980s,the sunshine hours was relatively less.[Conclusion] The research provided the guidance value for the adjustment of plantation structure and the transformation of agricultural developed manner in Puyang City.
基金Supported by National Science and Technology Support Plan(2009BAC53B02)National Natural Science Fund Item (41075103)Special Item of the Public Welfare Industry (Meteorology) Science and Research (GYHY201106034,GYHY201006023)
文摘[Objective]The research aimed to study variation characteristics of large-scale frost in the east region of the Yellow River of Gansu in recent 40 years.[Method]Based on daily minimum temperature data at 15 meteorological stations over the east region of the Yellow River of Gansu from 1969 to 2008,according to common climatic statistical index of the frost,variation characteristics of the large-scale frost and continuous frost in the east region of the Yellow River of Gansu in recent 40 years were studied.[Result]Since the 1990s,average last frost date in the east region of the Yellow River of Gansu obviously advanced,and first frost date started to obviously postpone.Advancing time of the last frost date was longer than postponing time of the first frost date.Average frost-free period also obviously prolonged.Extremely early first frost date and extremely late last frost date mainly happened in the 1970s and the 1980s.Extremely late first frost date and extremely early last frost date mainly happened after the middle period of the 1990s.Extremely long frost-free period gradually started to appear frequently.In recent 40 years,the continuous frost gradually decreased,and the intensity also declined.[Conclusion]The research was favorable for understanding change characteristics of the frost and climate in the east region of the Yellow River of Gansu,and had important guidance significance for improving prediction capability of the abnormal frost disaster,effectively preventing frost disaster and improving crop yield in the area.
文摘The geographical condition of Qingdao, China is relatively special;the transport of various inland pollutants, the emissions of marine aerosol and local pollutants will have an impact on the changes of atmospheric aerosol concentration. By using the stability classification method, trajectory clustering analysis and the NOAA HYSPLIT model, the seasonal distribution characteristics of atmospheric inhalable particulate matter concentration in Qingdao, China and its relationship with meteorological conditions, mixed layer height, and the seasonal characteristics of Qingdao pollutant transport were analyzed. The results show that the variation trends of PM2.5 and PM10 were about the same, and there are obvious seasonal differences, which are high in winter and spring, and low in summer and autumn. The concentration of inhalable particulate matter has a negative correlation with temperature, wind speed and relative humidity. The concentration of inhalable particulate matter is distinct in different relative humidity ranges. When the wind speed is less than 3 - 4 m/s, there are more inhalable particles, while the mass concentration shows obvious reduction with the wind speed more than 4 m/s. There is a significant negative correlation between the mass concentration of pollutants and the daily maximum mixed layer height. The larger the concentration of pollutants, the smaller the thickness of the daily largest mixed layer. Conversely, the smaller the mass concentration of pollutants, the larger the thickness of the daily largest mixed layer. The pollutant transport in Qingdao has obvious seasonal characteristics. The air mass in spring, autumn and winter is mainly medium-long distance transport from Mongolia and southern Russia, and medium-short distance transport from Inner Mongolia and northeast of China. The source of air masses in summer is mainly transported from the eastern and sea areas.
文摘[Objective] The research aimed to study variation characteristics of sunshine hours over Loess Plateau of Shaanxi during 1961-2010.[Method] By using the climate tendency rate,climate trend coefficient and linear correlation,the temporal and spatial variation characteristics of sunshine hours in Loess Plateau of Shaanxi in recent 50 years were analyzed.Moreover,the main reason for inducing variation of sunshine hours in the zone was discussed.[Result] In recent 50 years,the variation of annual sunshine hours in Loess Plateau of Shaanxi mainly presented decrease trend.The decrease zones were mainly located in windy desert region along the Great Wall line,central loess hilly region,most areas of plateau remains region and most areas of arid plateau region in north Weihe River.The increase zones were mainly located in west and northeast plateau remains region,southwest plateau remains region,some areas of arid plateau region in north Weihe River.Seen from four-season variation trend,except in spring,the sunshine hours in other seasons presented varying decrease trends.The decrease amplitude in summer was 24.34 h/10 a,and was the most significant.The second one was-16.62 h/10 a in winter.The decrease amplitude in winter was 3.55 h/10 a,and was unobvious.Seen from spatial variation,the annual sunshine hours presented significant increase trend in Mizhi of loess hilly region and significant decrease trend in Dingbian,Shenmu of windy desert region along the Great Wall line,Qingjian,Yanchuan of plateau remains region,Longxian,Fengxiang,Chunhua and Hancheng of arid plateau region in north Weihe River.There was no obvious variation trend in other research zones.The annual and four-season sunshine hours all presented negative correlations with rainfall,relative humidity,total cloud amount,low cloud amount,water vapor pressure and fog days.The sunshine hours presented positive correlation with visibility.The correlation coefficients between sunshine hours and relative humidity,rainfall,total cloud amount,water vapor pressure,fog days and visibility were all bigger in each region.[Conclusion] The research provided basis for analyzing climate variation over Loess Plateau of Shaanxi.
基金Supported by Special Item of Climate Variation of China Meteorological Administration ( CCFS-11-4)
文摘[Objective] The research aimed to study the variation characteristics of winter temperature in Jinan in recent 60 years.[Method] Based on winter monthly average,maximum and minimum temperatures in the ground observation station of Jinan during 1951-2010,by using linear trend,5-year moving average and anomaly,the variation characteristics of winter average,maximum and minimum temperatures in Jinan in recent 60 years were analyzed.The historical evolution trend and decadal variation characteristics were discussed.[Result] Winter average,maximum and minimum temperatures in Jinan in recent 60 years all presented slow fluctuation rise trend.The rise trend was obvious.Especially the increase amplitude of minimum temperature was the maximum.It illustrated that the variation of minimum temperature was more sensitive than that of maximum temperature,and the climatic warming in winter was mainly from the contribution of minimum temperature rise.Seen from the decadal variation,cold winter mainly appeared before the 1970s.Then,it presented obvious decrease trend.Conversely,warm winter presented increase trend after the 1970s.Warm winter phenomenon slowed after 2000.Winter temperature presented stepped warming trend during 1950s-1990s.Winter average temperature presented jumped warming trend when entered into the 1990s.The temperature presented downward trend when entered into the 21st century.But winter temperature still presented rise trend as a whole.The population growth in Jinan made that urbanization process accelerated,and urban heat island effect aggravated.It was one of important factors for climate warming in Jinan.[Conclusion] The research provided theoretical basis for understanding the long-term variation trend of climate in Jinan area,and if it was consistent with the background of global climatic warming.
基金Supported by Special Item of Climate Variation of China Meteorologcal Administration (CCSF2011-25)Guangxi Science Foundation Item (Guiqingke 0991060)
文摘[Objective] The research aimed to study the variation characteristics of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years.[Method] Based on the daily average temperature data from 1961 to 2010 at 88 meteorological stations in Guangxi,yearly days and end date of low temperature and rainy weather during spring sowing period were carried out statistics.The variation characteristics of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years were analyzed by using linear tendency calculation,phased analysis,Morlet wavelet analysis and correlation analysis.Moreover,the influences of climate warming on days and end date of low temperature and rainy weather in spring sowing period were analyzed.[Result] The average days of low temperature and rainy weather in Guangxi during spring sowing period from 1961 to 2010 was during 3.5-23.2 d.The regional distribution characteristics were that it was more in northeast and mountain zone,and less in southwest and valley.The regional distribution characteristics of end date were that it was late in northeast and mountain zone,and early in southwest and valley.The days of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years presented slight decrease trend,and the end date presented slight advancing trend.The phased variation characteristics of days and end date of low temperature and rainy weather were obvious.The days of low temperature and rainy weather from the early 1980s to metaphase of 1990s was obviously more,and the end date was obviously later.After the 1990s,the days of low temperature and rainy weather was obviously less,and the end date was obviously earlier.The days of low temperature and rainy weather had periodic oscillation signals of 4,6,8,10-14 years.The end date had periodic oscillation signals of 6,12-14 years.The days and end date of low temperature and rainy weather in Guangxi during spring sowing period significantly related to average temperature from middle dekad of February to first dekad of April.The climate warming made that the days of low temperature and rainy weather tended to decrease,and the end date tended to advance.[Conclusion] The research provided reference for further understanding the occurrence rule of low temperature and rainy weather,going after profits and avoiding disadvantages,reasonably arranging production,carrying out correlated research.
文摘[Objective] The aim was to study the variation characteristics of longest continuous rainfall days in Shenyang in recent 48 years. [Method] Based on the data of longest continuous rainfall days in Shenyang from May to September in 1961-2008, the variation characteristics of longest continuous rainfall days in Shenyang in recent 48 years was analyzed by means of one-dimensional linear trend estimation and wavelet analysis method. [Result] In recent 48 years, the longest continuous rainfall days in Shenyang showed decrease trend from May to September except for June in which it showed increased; the total longest continuous rainfall days showed decrease trend, and the maximum value appeared in 1986, while the minimum value could be found in 1997; from periodic variation, the total longest continuous rainfall days had the period of 2-3 years, and there also existed the period of 5-7 years after 1980; the total longest continuous rainfall days were more from the beginning of 1960s to the middle of 1990s and less thereafter. [Conclusion] The study could provide theoretical foundation for the deep research on climate change in Shenyang.
基金Supported by Special Item of Public Welfare Industry Science Research ( GYHY201006025)
文摘[Objective] The research aimed to study the variability and variation characteristics of climate in northern winter wheat zone during 1961-2004.[Method] Based on the meteorological data (temperature,precipitation and sunshine) of 55 meteorological stations in northern winter wheat zone during 1961-2004 and the yield data of winter wheat,by using the linear regression,correlated coefficient and climatic tendency rate,the spatial and temporal evolution characteristics of agricultural climatic resources (sunshine hours,temperature and precipitation) in northern winter wheat zone were analyzed.[Result] The annual average temperature,precipitation and sunshine hours in northern winter wheat zone during 1961-2004 all presented certain zonal distribution in the space.The precipitation and temperature gradually decreased from south to north.The sunshine hours gradually increased from south to north.The annual average temperature overall presented rise trend in northern winter wheat zone in 44 years,but the rise rate had difference in the different areas.The rise of annual average temperature in the high-latitude zone was more obvious than that in the low-latitude zone.The annual rainfall overall presented decrease trend,and the tendency rate of annual precipitation had significant difference in the different areas.The decrease rates of rainfalls in the central and western areas were bigger than that in other areas.The annual sunshine hours overall presented decline trend.In most areas,the tendency rate of annual sunshine hours was negative.But there was certain difference in the different areas.The zones where the decrease amplitude was smaller scattered in the west,and included central Shaanxi,south of Shanxi and some areas in southeast of Shandong.The decrease amplitudes were bigger in south of Henan,northwest of Shandong and south of Hebei.[Conclusion] The research provided theoretical basis for understanding the historical evolution of climate in northern winter wheat zone.
基金sponsored by the Key Project of Spark Program of Earthquake Sciences of Hebei Province Tectonic Characteristics of the Northern Section of Tangshan Fault and Its Relation with Earthquakes(DZ20190424079)。
文摘Based on the well water level data in Majiagou Mine in Tangshan City since 2000,it is suggested that the water level rise from 2008-2014 is possibly associated with reduced infiltration caused by less precipitation,together with the effect of less groundwater exploitation. However,the water level rise from 1992-1998 cannot be interpreted properly if we extend the data source back to 1991. After comparing the data with long-term water level data of five wells with different hydro-geological units in Tangshan and Qinhuangdao, the study indicates that the long-term water level variation cannot be only attributed to the effect of less precipitation and the control of groundwater exploitation,but also with the influence of regional stress field change.With the support of regional geological and tectonic information,combined with the comprehensive analysis of CBM data obtained from the coal field,new understandings of the dynamic characteristics of annual variation are obtained.
文摘Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline development. In most existing studies, remote sensing images are used to quantify the morphological characteristics of lakes. However, the extraction accuracy of lake water is greatly affected by cloud cover and vegetation cover, and the inversion accuracy of lake elevation data is poor, which cannot accurately describe the response relationship of lake landscape morphology with water level change. Therefore, this paper takes Tonle Sap Lake as the research object, which is the largest natural freshwater lake in Southeast Asia. DEM is constructed based on high-resolution measured topographic data, and morphological indicators such as lake area, lake shoreline length, perimeter area ratio, longest axis length, maximum width, shoreline development index, lake shape complexity, compactness ratio and form ratio are adopted to researching the evolution law of high water overflows and low water outbursts quantitatively, and clarifying the variation characteristics of landscape morphology with water level gradient in Tonle Sap Lake. The research results have important theoretical significance for the scientific utilization of Tonle Sap Lake water resources and the protection of the lake ecosystem.
基金supported by the National Natural Science Foundation of China (No.41605095)the Beijing Natural Science Foundation (No.JQ19030)+1 种基金the Beijing Municipal Commission of Education (No.PXM2019014213000007)the School Level Cultivation Fund of Beijing Technology and Business University for Distinguished and Excellent Young Scholars (No.BTBUYP2020)。
文摘A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle.The variation characteristics of fine particle matter(PM_(2.5)) and its components in diesel vehicle exhaust plumes were analyzed.The PM_(2.5) emissions gradually increased with increasing distance from the nozzle in the plume.Elemental carbon emissions remained basically unchanged, organic carbon and total carbon(TC) increased with increasing distance.The concentrations of SO_(4)^(2-),NO_(3)^(-) and NH_(4)^(+) (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume.The selective catalytic reduction(SCR) reduced 42.7% TC, 40% NO_(3)^(-) emissions, but increased 104% SO_(4)^(2-) and 36% NH_(4)^(+) emissions, respectively.In summary,the SCR reduced 29% primary PM_(2.5) emissions for the tested diesel vehicles.The NH_(4)NO_(3) particle formation maybe more important in the plume, and there maybe other forms of formation of NH_(4)^(+) (eg.NH4Cl).The generation of secondary organic carbon(SOC) plays a leading role in the generation of secondary PM_(2.5).The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process.The inconsistency between secondary organic aerosol(SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.
文摘[Objective] The aim was to study the characteristics of sunshine hour changes in Tacheng in recent 50 years.[Method] By dint of the measured data of annual,seasonal and monthly sunshine hour's changes in four meteorological observatories from 1960 to 2009,using linear regression analysis method,the characteristics of sunshine hour changes in Tacheng in recent 50 years were studied.[Result] The results showed that the annual average sunshine hours in Tacheng Basin in recent 50 years were above 2 800.0 h,among which Tacheng,Yumin had the most,2 936.1,2 921.3 h respectively and Emin the least,2 814.2 h.The sunshine hours were the most in autumn and summer,followed by winter,and were least in spring;sunshine hours during growth season in Tacheng and Yumin were the most,followed by Emin and then Tuoli.The linear tendency rate of sunshine hours in four stations in February was negative.But only the value in Tacheng,Emin decreased at a rate of-4.7 and-6.0 respectively;the linear tendency rate of sunshine hours in four stations in May,June and October were positive,but only Yumin station mounted at a rate of 14.5,12.6,11.2 h/10 a.The linear tendency of seasonal sunshine hours during the year and the growth season increased in Yumin at a rate of 74.9 and 60.5 h/10 a.The linear tendency rate of sunshine hours in four stations in winter was negative,among which the rate of Tacheng,Emin and Tuoli decreased at a rate of-5.5,-6.7,-4.9 h/10 a;that in other three seasons,only in Yumin,it increased most rapidly at a rate of 9.7,7.7 and 7.0 h/10 a.[Conclusion] The study provides theoretical reference for the adjustment and perfection of husbandry industry structure and optimization,reasonable development and utilization of solar energy resources.
基金supported by the the Special fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB22Z04).
文摘On July 29, 2021, a large earthquake of MW8.2 occurred south of the Alaska Peninsula. To investigate the spatial-temporal changes of crustal stress in the earthquake-stricken area before this event, we selected 159 earthquakes of 4.7 ≤ MW ≤ 6.9 that occurred in the epicentral region and its surroundings between January 1980 and June 2021 to study the temporal variation and spatial distribution of their apparent stress. In addition, we analyzed the correlation between seismic activities and Earth’s rotation and explored the seismogenic process of this earthquake. The crustal stress rose from January 2008 to December 2016. This period was followed by a sub-instability stage from January 2017 until the occurrence of the MW8.2 earthquake. The average rate of apparent stress change in the first five years of the stress increase period was roughly 2.3 times that in the last four years. The lateral distribution of the apparent stress shows that the areas with apparent stress greater than 1.0 MPa exhibited an expanding trend during the seismogenic process. The maximum apparent stress was located at the earthquake epicenter during the last four years. The distribution of the apparent stress in the E-W vertical cross section revealed that an apparent stress gap formed around the hypocenter during the first five years of the stress increase period, surrounded by areas of relatively high apparent stress. After the Alaska earthquake, most parts of this gap were filled in by aftershocks. The seismic activities during the sub-instability stage exhibited a significant correlation with Earth’s rotation.
基金Project of Science Planning of Guangdong Province (2005B32601007)Natural Science Foundation of China (41075073,40675055)
文摘Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year(1961-2005) and 86-station observational precipitation data of Guangdong,and the causes of drought events are discussed from different angles(e.g.,atmospheric circulation,sea surface temperature) on the basis of global coverage datasets of sea surface temperature and atmospheric elements.It is found that the occurrence frequency of persistent drought events in Guangdong province is once every 26 months on average,and autumn-winter or winter-spring persistent drought events take up the majority.The persistent drought events possess large scale spatial characteristics.While the 1960s is the most frequent and strongest decade of drought events in the latter half of the 20th century,the occurrence is more frequent and the intensity is stronger in the first five years of the 21st century(2001-2005).This reflects the response of regional extreme climatic events in Guangdong to global climatic change.The atmospheric circulation,sea surface temperature,etc,appear to have different abnormal characteristics when drought events happen in different seasons.The results of this paper provide some good reference information for the drought forecast,especially for the dynamic interpretation of climatic model products.
文摘[Objective] The research aimed to analyze temporal and spatial variation characteristics of temperature in Shangqiu City during 1961-2010.[Method] Based on temperature data in eight meteorological stations of Shangqiu during 1961-2010,by using trend analysis method,the temporal and spatial evolution characteristics of annual average temperature,annual average maximum and minimum temperatures,annual extreme maximum and minimum temperatures,daily range of annual average temperature in Shangqiu City were analyzed.M-K method was used to determine mutation year of temperature.[Result] The annual average temperature,annual average minimum temperature and annual extreme minimum temperature respectively rose at 0.122,0.255 and 0.488 ℃/10 a.The variation trend of annual average maximum temperature wasn't obvious.The daily range of annual average temperature and annual extreme maximum temperature respectively declined at-0.217 and-0.292 ℃/10 a.Seen from spatial distribution,the increase amplitudes of annual average temperature,annual average minimum temperature and annual extreme minimum temperature were all large in the east and small in the west.The decrease amplitude of daily range of annual average temperature was large in the east and small in the west.The decrease amplitude of annual extreme maximum temperature was large in the west and small in the east.The annual average maximum temperature had trends of increase and decrease.The annual average temperature,annual average minimum temperature and daily range of annual average temperature all mutated in 1997.The annual average maximum temperature didn't have obvious mutation point.The annual extreme maximum temperature mutated in 1973.The annual extreme minimum temperature respectively mutated in 1989 and 1999.[Conclusion] The research played important guidance significances in adjustment of agricultural production structure,regional climate planning,reasonably using climate resource and replying climate change in Shangqiu City.
文摘[Objective] The research aimed to study the variation rule of precipitation in the rainy season in Liupanshui City in recent 50 years. [Method] Based on the monthly precipitation data from three observatories (Liuzhi, Panxian and Shuicheng) of Liupanshui City from May to September during 1960-2009, the interannual, interdecadal variation and mutation characteristics of precipitation in the rainy season in Liupanshui City in recent 50 years were analyzed by using the linear tendency estimation, sliding T-test and Morlet wavelet analysis method. [Result] The rainfall in the rainy season in Liupanshui City in recent 50 years presented the decline trend, and the linear tendency rate was -15.4 mm/10 a. The precipitation in the rainy season in Liupanshui City had the obvious interannual and interdecadal variation characteristics. It was the obvious rainless period in the metaphase of 1960s, and the precipitation was comparatively more in late 1960s. It was the relatively rainless period in the whole 1970s. From late 1970s to late 1980s, the precipitation in the rainy season entered into the pluvial period, and it was the period when the precipitation was the most in recent 50 years. The precipitation was relatively less from late 1980s to metaphase of 1990s. It was the pluvial period in the middle and late periods of 1990s, and it was the rainless period when entered into the 21st century. The sliding T-test showed that the precipitation mutation point in the rainy season in Liupanshui City in recent 50 years was in 2002. The wavelet analysis showed that the precipitation in the rainy season in Liupanshui City had the significant multiple time scale characteristic. In the interdecadal scale, the precipitation had the significant 16-year periodic oscillation which stably existed in 50 years. In the interannual scale, the precipitation had the quasi-8-year periodic oscillation. [Conclusion] The research provided the scientific basis for the accurate forecast of drought and flood disasters, disaster prevention and reduction in the city.
