With different varieties of facility Hami melon(Cucumis melo var. sacchairinus) as test materials, the effects of meteorological conditions on the yield and quality of different varieties of facility Hami melon were a...With different varieties of facility Hami melon(Cucumis melo var. sacchairinus) as test materials, the effects of meteorological conditions on the yield and quality of different varieties of facility Hami melon were analyzed. The results showed that among the yield and quality traits of melon, the variation degree of average single melon weight was the highest, and the coefficient of variation was 33.05%. The variation degree of leaf area index was the lowest, and the coefficient of variation was 11.00%. Through the correlation analysis of meteorological factors with the yield and quality of facility Hami melon, it was found that the quality traits of facility Hami melon were significantly positively correlated with maximum temperature and sunshine duration, and significantly negatively correlated with precipitation. The yield traits were positively correlated with maximum temperature, sunshine duration and precipitation.展开更多
This work analyzes and discusses the influence of human activities on the meteorological conditions related to winter haze events in Beijing,Tianjin,and Hebei(i.e.,the Jing-Jin-Ji region)during 1961-2016,using the res...This work analyzes and discusses the influence of human activities on the meteorological conditions related to winter haze events in Beijing,Tianjin,and Hebei(i.e.,the Jing-Jin-Ji region)during 1961-2016,using the results of two numerical simulation experiments based on the Community Atmosphere Model version 5.1.1(http://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_1_1/book1.html)used in the international Climate Variability and Predictability Programme(CLIVAR)Climate of the 20th Century Detection and Attribution Project(C20C+D&A).The results show that,under the influence of human activities,the changes in dynamical and thermal meteorological conditions related to winter haze events in the Jing–Jin–Ji region are conducive to the formation and accumulation of haze,and prevent the diffusion of pollutants.The dynamical conditions mainly include the obvious weakening of the East Asian winter monsoon(EAWM)and the enhancement of the near-surface anomalous southerly wind.The thermal conditions include the obvious increase in surface temperature,and the enhancement of water vapor transport and near-surface inversion.The relative contribution of dynamical and thermal conditions to the variation of haze days in the Jing-Jin-Ji region is analyzed using statistical methods.The results show that the contribution of human activities to the increase of haze days in the Jing-Jin-Ji region is greater than that of natural forcing for the study period.To be specific,the dynamical meteorological factors contribute more to the haze days than the thermal meteorological factors.The contribution of thermal meteorological factors is basically the same in both scenarios.展开更多
To reveal the multivariate relationships between man-made and meteorological factors on dust storm frequency, the LUCC data, NDVI remote sensing data and meteorological data for the period of 1983-2013 were combined w...To reveal the multivariate relationships between man-made and meteorological factors on dust storm frequency, the LUCC data, NDVI remote sensing data and meteorological data for the period of 1983-2013 were combined with dust storm frequency data, and the possible impacts of meteorological and anthropogenic factors on dust storm frequency were analyzed by using regression analysis and PCA (Principal Component Analysis). Results show that the inter-annual dust storm frequency increased gradually. In particular, an increasing trend in recent years, after 2009, is conspicuous. The monthly frequency of dust storms shows higher values between the months of February and May, with the highest mean number of events occurring in April, which accounts for 29% of the annual dust storm frequency. The annual dust storm frequency is positively correlated with wind speed and negatively correlated with precipitation;the monthly dust storm frequency is positively correlated with wind speed, but no significant correlation can be found with precipitation. The relationship between temperature and dust storms is not simply linear, however, a certain correlation with an unremarkable statistical significance can be found between them. Human activities also affect the dynamics of dust storms indirectly via changing vegetation coverage and direct dust emissions. The multivariate analysis further confirmed the association between dust storm frequency and meteorological factors and NDVI. The high loadings of dust storm frequency, wind speed, precipitation and NDVI on a PC indicate that the increased precipitation and NDVI will decrease dust storm frequency, and increased wind speed will increase dust storm frequency.展开更多
Based on routine monitoring data of air quality and meteorological data in Shantou City during 2015-2019,temporal-spatial variation characteristics of O 3 pollution and its correlation with meteorological conditions i...Based on routine monitoring data of air quality and meteorological data in Shantou City during 2015-2019,temporal-spatial variation characteristics of O 3 pollution and its correlation with meteorological conditions in Shantou City were explored.The research results showed that O 3 pollution days in Shantou City showed an increasing trend year by year,and O 3 pollution had far-distance transportation and the development trend from offshore Nan ao Island to urban district.In spring and autumn,there was serious O 3 pollution,and it was the most prominent in October.Its diurnal variation in O 3 pollution days was mainly wide-peak type in the afternoon,showing as that O 3 concentration declined slowly after the noon.In O 3 pollution days,higher O 3 concentration was easy to appear at night,causing that O 3 peak in the second day was uplifted,and there was continuous O 3 pollution.Combining backward trajectory analysis chart,it was found that Shantou was mainly affected by coastal transport of northerly polluted air mass,and it was transported into Shantou City from the east to the northeast.O 3 from long-distance transmission superimposed with locally generated O 3,which commonly pushed up the level of O 3 concentration.The weather of O 3 pollution in Shantou City had the characteristics of high temperature and low humidity.There was 25-30℃of temperature interval and 46%-60%of relative humidity interval,and it was accompanied by grade-2 easterly wind.展开更多
Whole growth period of winter wheat and rape crops in western Guizhou in 2019 was from October of 2019 to early May of 2020.Using daily temperature,rainfall and sunshine hours of three national meteorological observat...Whole growth period of winter wheat and rape crops in western Guizhou in 2019 was from October of 2019 to early May of 2020.Using daily temperature,rainfall and sunshine hours of three national meteorological observatories(Shuicheng,Panzhou and Liuzhi)of western Guizhou,the impact of meteorological conditions on growth and development of winter wheat and rape crops was analyzed.The results showed that average temperature in whole growth period of winter wheat and rape crops in western Guizhou in 2019 was between 11.1 and 13.0℃,which was 0.4-1.6℃higher than that in the same period of common year.Rainfall was between 276.0 and 309.0 mm.When compared with that in the same period of common year,rainfall was 7%-22%less in other regions except in Panzhou(1%more).Sunshine hours was between 689.2 and 1091.2 h.When compared with that in the same period of common year,sunshine hours was 14%-26%more in other regions except in Shuicheng(equal).In growth period of winter wheat and rape crops,there was good heat condition and sufficient sunshine,and rainfall was normal and slightly less,but it was mostly sunny and rainy alternating,which was favorable for the growth of crop root.During growth period of crops,there was lighter meteorological disaster.It was clear that meteorological conditions were conducive to the growth and development of winter wheat and rape crops in 2019.展开更多
To guarantee the blue skies for the 2022 Winter Olympics held in Beijing and Zhangjiakou from February 4 to 20,Beijing and its surrounding areas adopted a series of emission control measures.This provides an opportuni...To guarantee the blue skies for the 2022 Winter Olympics held in Beijing and Zhangjiakou from February 4 to 20,Beijing and its surrounding areas adopted a series of emission control measures.This provides an opportunity to determine the impacts of large-scale temporary control measures on the air quality in Beijing during this special period.Here,we applied the WRF-CMAQ model to quantify the contributions of emission reduction measures and meteorological conditions.Results show that meteorological conditions in 2022 decreased PM_(2.5)in Beijing by 6.9 and 11.8μg/m^(3)relative to 2021 under the scenarios with and without emission reductions,respectively.Strict emission reduction measures implemented in Beijing and seven neighboring provinces resulted in an average decrease of 13.0μg/m^(3)(-41.2%)in PM_(2.5)in Beijing.Over the entire period,local emission reductions contributed more to good air quality in Beijing than nonlocal emission reductions.Under the emission reduction scenario,local,controlled regions,other regions,and boundary conditions contributed 47.7%,42.0%,5.3%,and 5.0%to the PM_(2.5)concentrations in Beijing,respectively.The results indicate that during the cleaning period with the air masses from the northwest,the abatements of PM_(2.5)were mainly caused by local emission reductions.However,during the potential pollution period with the air masses from the east-northeast and west-southwest,the abatements of PM_(2.5)were caused by both local and nonlocal emission reductions almost equally.This implies that regional coordinated prevention and control strategies need to be arranged scientifically and rationally when heavy pollution events are forecasted.展开更多
Meteorological conditions have an important impact on changes of vegetation in ecologically fragile karst areas.This study aims to explore a method for quantitative evaluation of these meteorological conditions. We an...Meteorological conditions have an important impact on changes of vegetation in ecologically fragile karst areas.This study aims to explore a method for quantitative evaluation of these meteorological conditions. We analyzed the changing trend of vegetation during 2000–2018 and the correlations between vegetation changes and various meteorological factors in karst rocky areas of Guangxi Zhuang Autonomous Region, China. Key meteorological factors in vegetation areas with varying degrees of improvement were selected and evaluated at seasonal timescale. A quantitative evaluation model of comprehensive influences of meteorological factors on vegetation was built by using the partial least-square regression(PLS). About 91.45% of the vegetation tended to be improved, while only the rest 8.55% showed a trend of degradation from 2000 to 2018. Areas with evident vegetation improvement were mainly distributed in the middle and northeast, and those with obvious vegetation degradation were scattered. Meteorological factors affecting vegetation were significantly different among the four seasons. Overall, high air humidity, small temperature difference in spring and autumn, and low daily minimum temperature and air pressure were favorable conditions. Low temperature in winter as well as high temperature in summer and autumn were unfavorable conditions. The Climate Vegetation Index(CVI) model was established by PLS using the maximum, minimum, and average temperatures;vapor pressure;rainfall;and air pressure as key meteorological factors. The Enhanced Vegetation Index(EVI) was well fitted by the CVI model, with the average coefficient of determination(r2) and root mean square error(RMSE) of 0.856 and 0.042, respectively. Finally, an assessment model of comprehensive meteorological conditions was built based on the interannual differences in CVI. The meteorological conditions in the study area in 2014 were successfully evaluated by combining the model and selected seasonal key meteorological factors.展开更多
To investigate the interannual variations of particulate matter(PM) pollution in winter, this paper examines the pollution characteristics of PM with aerodynamic diameters of less than 2.5 and 10 μm(i.e., PM_(2.5) an...To investigate the interannual variations of particulate matter(PM) pollution in winter, this paper examines the pollution characteristics of PM with aerodynamic diameters of less than 2.5 and 10 μm(i.e., PM_(2.5) and PM10), and their relationship to meteorological conditions over the Beijing municipality, Tianjin municipality, and Hebei Province—an area called Jing–Jin–Ji(JJJ, hereinafter)—in December 2013–16. The meteorological conditions during this period are also analyzed. The regional average concentrations of PM_(2.5)(PM10) over the JJJ area during this period were 148.6(236.4), 100.1(166.4), 140.5(204.5), and 141.7(203.1) μg m^(–3), respectively. The high occurrence frequencies of cold air outbreaks, a strong Siberian high, high wind speeds and boundary layer height, and low temperature and relative humidity, were direct meteorological causes of the low PM concentration in December 2014. A combined analysis of PM pollution and meteorological conditions implied that control measures have resulted in an effective improvement in air quality. Using the same emissions inventory in December 2013–16, a modeling analysis showed emissions of PM_(2.5) to decrease by 12.7%, 8.6%, and 8.3% in December 2014, 2015, and 2016, respectively,each compared with the previous year, over the JJJ area.展开更多
Spray drift has always been a focus research area in the field of unmanned aerial vehicle(UAV)application.Under the fixed premises of UAV operating parameters,such as height,speed and spraying liquid,the droplet drift...Spray drift has always been a focus research area in the field of unmanned aerial vehicle(UAV)application.Under the fixed premises of UAV operating parameters,such as height,speed and spraying liquid,the droplet drift is mainly affected by meteorological conditions.In this research,the spray drift and deposition tests were conducted using a QuanFeng120 UAV in a pineapple field under various different meteorological conditions.The experimental results showed that with the changes of UAV operating height and wind speed,the start position of the in-swath deposition area changed 4 m in the extreme situation.The percentage of the total spray drift was from 15.42%to 55.76%.The position of cumulative spray drift that accounted for 90%of the total spray drift was from 3.70 m to 46.50 m relative to the flight line.According to the downwind spray drift curve,the nonlinear equations of the same type under the four operating conditions of the UAV were fitted.The spray drift and the deposition of UAV application were significantly affected by different meteorological conditions and UAV operating heights.The results could provide a theoretical basis for UAV spraying in pineapple plants and support for spray drift control and prediction.展开更多
Based on the ozone monitoring data from the Bengbu Environmental Monitoring Station and the meteorological observation data from the Bengbu Ground Meteorological Observation Station from 2015 to 2019,the changing tren...Based on the ozone monitoring data from the Bengbu Environmental Monitoring Station and the meteorological observation data from the Bengbu Ground Meteorological Observation Station from 2015 to 2019,the changing trend of ozone concentration and the effects of meteorological conditions on ozone concentration in Bengbu in recent years were analyzed.The results show that from 2015 to 2019,the monthly and daily changing curves of ozone concentration in Bengbu City had double peaks and a single peak respectively.The peak of monthly average ozone concentration appeared from April to June and in September.The peak of daily average ozone concentration occurred around 16:00,while the valley apppeared around 07:00.Among the main meteorological factors affecting ozone concentration,ozone concentration was significantly positively correlated with temperature and sunshine hours and significantly negatively correlated with relative humidity,air pressure,total cloud cover,and wind speed.展开更多
Using the WRF mesoscale numerical model,based on the FNL global reanalysis data of NCEP,numerical simulations with a resolution of 27,9 and 3 km were carried out on the meteorological elements in four national air qua...Using the WRF mesoscale numerical model,based on the FNL global reanalysis data of NCEP,numerical simulations with a resolution of 27,9 and 3 km were carried out on the meteorological elements in four national air quality control stations(Jinyun Mountain,Shapingba,Jiefangbei and Nanping)in the main urban area of Chongqing City in July from 2013 to 2015.The results show that at the concerned points,there was an obvious southeast dominant wind at 850 hPa.The meteorological conditions in July in the main urban area of Chongqing were favorable for the diffusion of pollutants.That is,the height of the mixed layer was higher,and the precipitation was higher;the temperature and wind speed at 850 hPa were higher.Compared with 2013 and 2014,the meteorological conditions in July 2015 were not more favorable for the diffusion of pollutants.展开更多
Based on the circumfluence situation of the out- and in-Tibet Plateau Vortex (TPV) from 1998-2004 and its weather-influencing system,multiple synthesized physical fields in the middle-upper troposphere of the out- and...Based on the circumfluence situation of the out- and in-Tibet Plateau Vortex (TPV) from 1998-2004 and its weather-influencing system,multiple synthesized physical fields in the middle-upper troposphere of the out- and in-TPV are computationally analyzed by using re-analysis data from National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) of United States.Our research shows that the departure of TPV is caused by the mutual effects among the weather systems in Westerlies and in the subtropical area,within the middle and the upper troposphere.This paper describes the large-scale meteorological condition and the physics image of the departure of TPV,and the main differences among the large-scale conditions for all types of TPVs.This study could be used as the scientific basis for predicting the torrential rain and the floods caused by the TPV departure.展开更多
It is still not well understood if subseasonal variability of the local PM_(2.5) in the Beijing-Tianjin-Hebei(BTH)region is affected by the stratospheric state.Using PM_(2.5) observations and the ERA5 reanalysis,the e...It is still not well understood if subseasonal variability of the local PM_(2.5) in the Beijing-Tianjin-Hebei(BTH)region is affected by the stratospheric state.Using PM_(2.5) observations and the ERA5 reanalysis,the evolution of the air quality in BTH during the January 2021 sudden stratospheric warming(SSW)is explored.The subseasonal variability of the PM_(2.5) concentration after the SSW onset is evidently enhanced.Stratospheric circumpolar easterly anomalies lasted for 53 days during the January-February 2021 SSW with two evident stratospheric pulses arriving at the ground.During the tropospheric wave weakening period and the intermittent period of dormant stratospheric pulses,the East Asian winter monsoon weakened,anomalous temperature inversion developed in the lower troposphere,anomalous surface southerlies prevailed,atmospheric moisture increased,and the boundary layer top height lowered,all of which favor the accumulation of pollutant particulates,leading to two periods of pollution processes in the BTH region.In the phase of strengthened East Asian winter monsoon around the very beginning of the SSW and another two periods when stratospheric pulses had reached the near surface,opposite-signed circulation patterns and meteorological conditions were observed,which helped to dilute and diffuse air pollutants in the BTH region.As a result,the air quality was excellent during the two periods when the stratospheric pulse had reached the near surface.The increased subseasonal variation of the regional pollutant particulates after the SSW onset highlights the important role of the stratosphere in the regional environment and provides implications for the environmental prediction.展开更多
The causes of persistent haze pollution in Jiujiang City from the end of November to the beginning of December 2016 are analyzed. The results show that there were three main long-distance paths to transport fine parti...The causes of persistent haze pollution in Jiujiang City from the end of November to the beginning of December 2016 are analyzed. The results show that there were three main long-distance paths to transport fine particles to Jiujiang. The upstream guide wind and the local static weather conditions made local pollutants superimposed on the particulate matter. The first source emission and two conversion of different inorganic pollutants contributed to the increase in the concentration of particles in Jiujiang. High temperature and high humidity could promote the formation of two organic particles. But when temperature was low in winter,the increase of energy consumption made local source emission increase. The high molecular weight semi-volatile organic compounds in the air were adsorbed on the surface of the particles,and the haze was gradually formed through the process of hygroscopic growth and the aging of particles. Jiujiang's natural landform,the " valley wind" circulation effect of dominant wind,and the radiation effect of aerosol were favorable for the accumulation of pollutants in Jiujiang.展开更多
According to the air quality monitoring and meteorological observation data from 2015 to 2020,the air pollution characteristics and causes were analyzed in the Ghost Festival(on the 15 th of the 7 th lunar month)for t...According to the air quality monitoring and meteorological observation data from 2015 to 2020,the air pollution characteristics and causes were analyzed in the Ghost Festival(on the 15 th of the 7 th lunar month)for the main urban area of Liupanshui City in western Guizhou Province.The results showed that air pollution to different extent occurred in the Ghost Festival every year,reaching the level of heavy pollution in half of the year.The pollution time is generally from 21:00 on the day to 01:00 on the next day.The pollutants mainly come from the smoke dust generated by people burning sacrificial offerings and industrial pollution of iron and steel manufacturing under adverse weather conditions.The primary pollutant is PM 2.5,and the annual variation of pollution shows a downward trend.Precipitation weather is in the majority,which is favorable for reducing the pollution degree;the relationship between wind direction,wind speed and pollution degree is closed;the atmospheric inversion is weak,which has no obvious influence on the change of air pollution;the relative humidity is high,which is conducive to the formation and maintenance of pollution;there is a very significant negative correlation between the degree of air pollution and wind energy,and significantly negative correlation between the degree of air pollution and atmospheric turbulence intensity.Advocating civilized sacrifice and strengthening management is beneficial to reducing the degree of pollution.This paper can be used as a reference for air quality forecasts and taking the appropriate measures to reduce pollution.展开更多
This study mainly introduces a large-scale heavy haze weather process in northern China from November 11 to 17, 2020, and analyzes the weather process. Methods such as comparative analysis and data analysis were used ...This study mainly introduces a large-scale heavy haze weather process in northern China from November 11 to 17, 2020, and analyzes the weather process. Methods such as comparative analysis and data analysis were used in this study. The main reasons for the formation of smog are as follows. First, the relative humidity is high and the water vapor content is relatively high. Second, the atmosphere is in a static and stable state, and suspended particulate matter in the atmosphere is not easy to diffuse and dilute, so it will gradually accumulate in urban areas and suburban areas. Third, there is a temperature inversion in the vertical direction, and the suspended particles in the air are difficult to drift to high altitudes and are blocked at low altitudes and near the ground. Fourth, there must be cooling conditions. Meteorological factors are the external causes for the formation of smog. And inversion intensity has a negative correlation with visibility, which has some indicating importance in fog and haze predictions. Large-scale haze weather mainly occurs in the large-scale atmospheric circulation with weak cold air and good water vapor conditions, and wind near the ground is small. Due to the high humidity in haze weather, fog droplets provide adsorption and reaction sites, accelerating the conversion of gaseous pollutants to liquid particles. At the same time, particles are also easy to act as condensation nucleus to accelerate the generation of haze. When the two interact, the pollutants are not easy to diffuse outward, resulting in agglomeration effect, and the pollution is getting heavier.展开更多
The article is devoted to the discussion of the advantages of assessing the environmental comfort of the climate,based on the natural features of the climate and the bioclimatic conditions of the territory.The study a...The article is devoted to the discussion of the advantages of assessing the environmental comfort of the climate,based on the natural features of the climate and the bioclimatic conditions of the territory.The study assessed the ecological comfort of the climate in the city of Taganrog on the basis of the developed original sequence of performing three stages of assessing the totality of bioclimatic indicators with the final calculation of the values of the integral indicator of the bioclimatic comfort of the climate.The results of the assessment showed,according to the average long-term climatic data,the presence of sub-comfortable climates with a tendency to transition to comfortable climate conditions in the warm period of the year.The cold season was distinguished by uncomfortable conditions according to long-term average climatic data.Modeling calculations of the possible risk to the health of city residents in the presence of concentrations of suspended solids in the surface air layer,together with carbon monoxide,exceeding the maximum one-time values by more than 7 times,showed that the development of possible resorptive or carcinogenic effects in these circumstances will occur in 1/3 the population of the city.The prospects for the assessment of the ecological comfort of the climate,which allow in the future to adequately calculate the magnitude of environmental risks to public health caused by pollution of the surface air layer,are shown.展开更多
Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions,one of the associated basic tasks.As one of three potential sites to host the 12-me...Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions,one of the associated basic tasks.As one of three potential sites to host the 12-meter Large Optical/infrared Telescope(LOT),the Muztagh-ata site,which is located on the Pamir Plateau in Xinjiang,in west China,began its site-testing task in the spring of 2017.In this paper,we firstly start with an introduction to the site and then present a statistical analysis of the ground-level meteorological properties such as air temperature,barometric pressure,relative humidity,and wind speed and direction,recorded by an automatic weather station with standard meteorological sensors for a two-year duration.We also show the monitoring results of sky brightness during this period.展开更多
An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017.73 out of 96 selected cities,most located in the Beijing-TianjinHebei and the surrounding area(BTHS),s...An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017.73 out of 96 selected cities,most located in the Beijing-TianjinHebei and the surrounding area(BTHS),suffered severe ozone pollution.A north-south contrast ozone distribution,with higher ozone(199±33μg/m3)in the BTHS and lower ozone(118±25μg/m^3)in the Yangtze River Delta(YRD),was found to be dominated by the position of the West Pacific Subtropical High(WPSH)and mid-high latitude wave activities.In the BTHS,the positive anomalies of geopotential height at 500 hPa and temperature at the surface indicated favorable meteorological conditions for local ozone formation.Prevailing northwesterly winds in the mid-high troposphere and warm advection induced by weak southerly winds in the low troposphere resulted in low-moderate relative humidity(RH),less total cloud cover(TGC),strong solar radiation and high temperatures.Moreover,southerly winds prevailing over the BTHS aggravated the pollution due to regional transportation of O3 and its precursors.On one hand,the deep sinking motion and inversion layer suppressed the dispersion of pollutants.On the other hand,O3-rich air in the upper layer was maintained at night due to temperature inversion,which facilitated O3 vertical transport to the surface in the next-day morning due to elevated convection.Generally,temperature,UV radiation,and RH showed good correlations with O3 in the BTHS,with rates of 8.51(μg/m^3)/℃(within the temperature range of 20-38℃),59.54(μg/m^3)/(MJ/m^2)and-1.93(μg/m^3)/%,respectively.展开更多
An upswing in haze weather during autumn and winter has been observed over North and Northeast China in recent years, imposing adverse impacts upon local socioeconomic development and human health. However, such an in...An upswing in haze weather during autumn and winter has been observed over North and Northeast China in recent years, imposing adverse impacts upon local socioeconomic development and human health. However, such an increase in the occurrence of haze events and its association with natural climate variability and climate change are not well understood. To investigate the climatology of the meteorological factors associated with haze events and their natural variability, this study uses a meteorological pollution index called PLAM(Parameter Linking Air-quality to Meteorological conditions) and ERA-Interim reanalysis data. The results suggest that high PLAM values tend to occur over southern parts of northern China, implying the weather conditions over this area are favorable for the occurrence of haze weather. For the period 1979–2014, the regional mean PLAM shows an overall increase across Beijing, Tianjin, and Hebei Province, and parts of Shanxi Province. Also, a periodicity of 28–34 months is found in the temporal variation of PLAM, which implies a potential association of PLAM with the stratospheric Quasi-Biannual Oscillation(QBO). By using the QBO index during the autumn and winter seasons in the preceding year, an increase in PLAM is found for the westerly phases of the QBO, relative to the easterly phases. An upper-tropospheric warming is also found in the westerly phases, which can induce a stable stratification that favors the increase in PLAM across the midlatitudes. The modulations of large-scale environmental factors, including moist static stability,vertical velocity, and temperature advection, also act to enhance PLAM in the westerly phases. However, the baroclinic term of moist potential vorticity at 700 hPa tends to decrease over the south, and an increase in low-level ascent is found over the north. These factors can reduce PLAM and possibly limit the statistical significance of the increased PLAM in the westerly phases of the QBO.展开更多
基金Supported by Project of Shandong Institute of Modern Agriculture of Zhejiang University for Serving Local Economic Development (ZDNY-2020-FWLY2006)。
文摘With different varieties of facility Hami melon(Cucumis melo var. sacchairinus) as test materials, the effects of meteorological conditions on the yield and quality of different varieties of facility Hami melon were analyzed. The results showed that among the yield and quality traits of melon, the variation degree of average single melon weight was the highest, and the coefficient of variation was 33.05%. The variation degree of leaf area index was the lowest, and the coefficient of variation was 11.00%. Through the correlation analysis of meteorological factors with the yield and quality of facility Hami melon, it was found that the quality traits of facility Hami melon were significantly positively correlated with maximum temperature and sunshine duration, and significantly negatively correlated with precipitation. The yield traits were positively correlated with maximum temperature, sunshine duration and precipitation.
基金This study was jointly supported by the National Key Research and Development Program of China(2017YF0603703 and 2017YF0605004)the Atmospheric Pollution Control of the Prime Minister Fund of China(DQGG0104).
文摘This work analyzes and discusses the influence of human activities on the meteorological conditions related to winter haze events in Beijing,Tianjin,and Hebei(i.e.,the Jing-Jin-Ji region)during 1961-2016,using the results of two numerical simulation experiments based on the Community Atmosphere Model version 5.1.1(http://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_1_1/book1.html)used in the international Climate Variability and Predictability Programme(CLIVAR)Climate of the 20th Century Detection and Attribution Project(C20C+D&A).The results show that,under the influence of human activities,the changes in dynamical and thermal meteorological conditions related to winter haze events in the Jing–Jin–Ji region are conducive to the formation and accumulation of haze,and prevent the diffusion of pollutants.The dynamical conditions mainly include the obvious weakening of the East Asian winter monsoon(EAWM)and the enhancement of the near-surface anomalous southerly wind.The thermal conditions include the obvious increase in surface temperature,and the enhancement of water vapor transport and near-surface inversion.The relative contribution of dynamical and thermal conditions to the variation of haze days in the Jing-Jin-Ji region is analyzed using statistical methods.The results show that the contribution of human activities to the increase of haze days in the Jing-Jin-Ji region is greater than that of natural forcing for the study period.To be specific,the dynamical meteorological factors contribute more to the haze days than the thermal meteorological factors.The contribution of thermal meteorological factors is basically the same in both scenarios.
文摘To reveal the multivariate relationships between man-made and meteorological factors on dust storm frequency, the LUCC data, NDVI remote sensing data and meteorological data for the period of 1983-2013 were combined with dust storm frequency data, and the possible impacts of meteorological and anthropogenic factors on dust storm frequency were analyzed by using regression analysis and PCA (Principal Component Analysis). Results show that the inter-annual dust storm frequency increased gradually. In particular, an increasing trend in recent years, after 2009, is conspicuous. The monthly frequency of dust storms shows higher values between the months of February and May, with the highest mean number of events occurring in April, which accounts for 29% of the annual dust storm frequency. The annual dust storm frequency is positively correlated with wind speed and negatively correlated with precipitation;the monthly dust storm frequency is positively correlated with wind speed, but no significant correlation can be found with precipitation. The relationship between temperature and dust storms is not simply linear, however, a certain correlation with an unremarkable statistical significance can be found between them. Human activities also affect the dynamics of dust storms indirectly via changing vegetation coverage and direct dust emissions. The multivariate analysis further confirmed the association between dust storm frequency and meteorological factors and NDVI. The high loadings of dust storm frequency, wind speed, precipitation and NDVI on a PC indicate that the increased precipitation and NDVI will decrease dust storm frequency, and increased wind speed will increase dust storm frequency.
基金Guangdong Science and Technology Special Project in 2019(2019ST084).
文摘Based on routine monitoring data of air quality and meteorological data in Shantou City during 2015-2019,temporal-spatial variation characteristics of O 3 pollution and its correlation with meteorological conditions in Shantou City were explored.The research results showed that O 3 pollution days in Shantou City showed an increasing trend year by year,and O 3 pollution had far-distance transportation and the development trend from offshore Nan ao Island to urban district.In spring and autumn,there was serious O 3 pollution,and it was the most prominent in October.Its diurnal variation in O 3 pollution days was mainly wide-peak type in the afternoon,showing as that O 3 concentration declined slowly after the noon.In O 3 pollution days,higher O 3 concentration was easy to appear at night,causing that O 3 peak in the second day was uplifted,and there was continuous O 3 pollution.Combining backward trajectory analysis chart,it was found that Shantou was mainly affected by coastal transport of northerly polluted air mass,and it was transported into Shantou City from the east to the northeast.O 3 from long-distance transmission superimposed with locally generated O 3,which commonly pushed up the level of O 3 concentration.The weather of O 3 pollution in Shantou City had the characteristics of high temperature and low humidity.There was 25-30℃of temperature interval and 46%-60%of relative humidity interval,and it was accompanied by grade-2 easterly wind.
基金Supported by Science and Technology Plan Project of Liupanshui City(52020-2015-30)Provincial and Municipal Science and Technology Cooperation Project(52020-2015-01-02).
文摘Whole growth period of winter wheat and rape crops in western Guizhou in 2019 was from October of 2019 to early May of 2020.Using daily temperature,rainfall and sunshine hours of three national meteorological observatories(Shuicheng,Panzhou and Liuzhi)of western Guizhou,the impact of meteorological conditions on growth and development of winter wheat and rape crops was analyzed.The results showed that average temperature in whole growth period of winter wheat and rape crops in western Guizhou in 2019 was between 11.1 and 13.0℃,which was 0.4-1.6℃higher than that in the same period of common year.Rainfall was between 276.0 and 309.0 mm.When compared with that in the same period of common year,rainfall was 7%-22%less in other regions except in Panzhou(1%more).Sunshine hours was between 689.2 and 1091.2 h.When compared with that in the same period of common year,sunshine hours was 14%-26%more in other regions except in Shuicheng(equal).In growth period of winter wheat and rape crops,there was good heat condition and sufficient sunshine,and rainfall was normal and slightly less,but it was mostly sunny and rainy alternating,which was favorable for the growth of crop root.During growth period of crops,there was lighter meteorological disaster.It was clear that meteorological conditions were conducive to the growth and development of winter wheat and rape crops in 2019.
基金supported by the National Natural Science Foundation of China (Nos.42175084,21577126,and 41561144004)the Department of Science and Technology of China (Nos.2018YFC0213506,2018YFC0213503,and 2016YFC0202702)+4 种基金the National Research Program for Key Issues in Air Pollution Control in China (No.DQGG0107)supported by the“Zhejiang 1000 Talent Plan”and Research Center for Air Pollution and Health in Zhejiang UniversityPengfei Li is supported by the National Natural Science Foundation of China (No.22006030)the Initiation Fund for Introducing Talents of Hebei Agricultural University (No.412201904)the Hebei Youth Top Q15 Fund (No.BJ2020032)。
文摘To guarantee the blue skies for the 2022 Winter Olympics held in Beijing and Zhangjiakou from February 4 to 20,Beijing and its surrounding areas adopted a series of emission control measures.This provides an opportunity to determine the impacts of large-scale temporary control measures on the air quality in Beijing during this special period.Here,we applied the WRF-CMAQ model to quantify the contributions of emission reduction measures and meteorological conditions.Results show that meteorological conditions in 2022 decreased PM_(2.5)in Beijing by 6.9 and 11.8μg/m^(3)relative to 2021 under the scenarios with and without emission reductions,respectively.Strict emission reduction measures implemented in Beijing and seven neighboring provinces resulted in an average decrease of 13.0μg/m^(3)(-41.2%)in PM_(2.5)in Beijing.Over the entire period,local emission reductions contributed more to good air quality in Beijing than nonlocal emission reductions.Under the emission reduction scenario,local,controlled regions,other regions,and boundary conditions contributed 47.7%,42.0%,5.3%,and 5.0%to the PM_(2.5)concentrations in Beijing,respectively.The results indicate that during the cleaning period with the air masses from the northwest,the abatements of PM_(2.5)were mainly caused by local emission reductions.However,during the potential pollution period with the air masses from the east-northeast and west-southwest,the abatements of PM_(2.5)were caused by both local and nonlocal emission reductions almost equally.This implies that regional coordinated prevention and control strategies need to be arranged scientifically and rationally when heavy pollution events are forecasted.
基金Supported by the Guangxi Zhuang Autonomous Region (GZAR) Science and Technology Project (AB20159022 and AB17292051)GZAR Natural Science Foundation (2018GXNSFAA281338)。
文摘Meteorological conditions have an important impact on changes of vegetation in ecologically fragile karst areas.This study aims to explore a method for quantitative evaluation of these meteorological conditions. We analyzed the changing trend of vegetation during 2000–2018 and the correlations between vegetation changes and various meteorological factors in karst rocky areas of Guangxi Zhuang Autonomous Region, China. Key meteorological factors in vegetation areas with varying degrees of improvement were selected and evaluated at seasonal timescale. A quantitative evaluation model of comprehensive influences of meteorological factors on vegetation was built by using the partial least-square regression(PLS). About 91.45% of the vegetation tended to be improved, while only the rest 8.55% showed a trend of degradation from 2000 to 2018. Areas with evident vegetation improvement were mainly distributed in the middle and northeast, and those with obvious vegetation degradation were scattered. Meteorological factors affecting vegetation were significantly different among the four seasons. Overall, high air humidity, small temperature difference in spring and autumn, and low daily minimum temperature and air pressure were favorable conditions. Low temperature in winter as well as high temperature in summer and autumn were unfavorable conditions. The Climate Vegetation Index(CVI) model was established by PLS using the maximum, minimum, and average temperatures;vapor pressure;rainfall;and air pressure as key meteorological factors. The Enhanced Vegetation Index(EVI) was well fitted by the CVI model, with the average coefficient of determination(r2) and root mean square error(RMSE) of 0.856 and 0.042, respectively. Finally, an assessment model of comprehensive meteorological conditions was built based on the interannual differences in CVI. The meteorological conditions in the study area in 2014 were successfully evaluated by combining the model and selected seasonal key meteorological factors.
基金Supported by the National Natural Science Foundation of China(91544232 and 51305112)Chinese Academy of Meteorological Sciences Basic Research Project(2017Y001)National Science and Technology Support Program of China(2014BAC16B03 and2014BAC23B01)
文摘To investigate the interannual variations of particulate matter(PM) pollution in winter, this paper examines the pollution characteristics of PM with aerodynamic diameters of less than 2.5 and 10 μm(i.e., PM_(2.5) and PM10), and their relationship to meteorological conditions over the Beijing municipality, Tianjin municipality, and Hebei Province—an area called Jing–Jin–Ji(JJJ, hereinafter)—in December 2013–16. The meteorological conditions during this period are also analyzed. The regional average concentrations of PM_(2.5)(PM10) over the JJJ area during this period were 148.6(236.4), 100.1(166.4), 140.5(204.5), and 141.7(203.1) μg m^(–3), respectively. The high occurrence frequencies of cold air outbreaks, a strong Siberian high, high wind speeds and boundary layer height, and low temperature and relative humidity, were direct meteorological causes of the low PM concentration in December 2014. A combined analysis of PM pollution and meteorological conditions implied that control measures have resulted in an effective improvement in air quality. Using the same emissions inventory in December 2013–16, a modeling analysis showed emissions of PM_(2.5) to decrease by 12.7%, 8.6%, and 8.3% in December 2014, 2015, and 2016, respectively,each compared with the previous year, over the JJJ area.
基金We acknowledge that this work was financially supported by the National Key Technologies Research and Development Program(2016YFD0200700)Guangdong Leading Talent Project(2016LJ06G689)+2 种基金111 Project(D18019)Educational Commission of Guangdong Province of China for Platform Construction(2015KGJHZ007)Science and Technology Planning Project of Guangdong(2017B010117010).
文摘Spray drift has always been a focus research area in the field of unmanned aerial vehicle(UAV)application.Under the fixed premises of UAV operating parameters,such as height,speed and spraying liquid,the droplet drift is mainly affected by meteorological conditions.In this research,the spray drift and deposition tests were conducted using a QuanFeng120 UAV in a pineapple field under various different meteorological conditions.The experimental results showed that with the changes of UAV operating height and wind speed,the start position of the in-swath deposition area changed 4 m in the extreme situation.The percentage of the total spray drift was from 15.42%to 55.76%.The position of cumulative spray drift that accounted for 90%of the total spray drift was from 3.70 m to 46.50 m relative to the flight line.According to the downwind spray drift curve,the nonlinear equations of the same type under the four operating conditions of the UAV were fitted.The spray drift and the deposition of UAV application were significantly affected by different meteorological conditions and UAV operating heights.The results could provide a theoretical basis for UAV spraying in pineapple plants and support for spray drift control and prediction.
文摘Based on the ozone monitoring data from the Bengbu Environmental Monitoring Station and the meteorological observation data from the Bengbu Ground Meteorological Observation Station from 2015 to 2019,the changing trend of ozone concentration and the effects of meteorological conditions on ozone concentration in Bengbu in recent years were analyzed.The results show that from 2015 to 2019,the monthly and daily changing curves of ozone concentration in Bengbu City had double peaks and a single peak respectively.The peak of monthly average ozone concentration appeared from April to June and in September.The peak of daily average ozone concentration occurred around 16:00,while the valley apppeared around 07:00.Among the main meteorological factors affecting ozone concentration,ozone concentration was significantly positively correlated with temperature and sunshine hours and significantly negatively correlated with relative humidity,air pressure,total cloud cover,and wind speed.
基金Supported by the Special Project for the Performance Incentive Guidance of Scientific Research Institutions in Chongqing City(cstc2021jxjl20020)。
文摘Using the WRF mesoscale numerical model,based on the FNL global reanalysis data of NCEP,numerical simulations with a resolution of 27,9 and 3 km were carried out on the meteorological elements in four national air quality control stations(Jinyun Mountain,Shapingba,Jiefangbei and Nanping)in the main urban area of Chongqing City in July from 2013 to 2015.The results show that at the concerned points,there was an obvious southeast dominant wind at 850 hPa.The meteorological conditions in July in the main urban area of Chongqing were favorable for the diffusion of pollutants.That is,the height of the mixed layer was higher,and the precipitation was higher;the temperature and wind speed at 850 hPa were higher.Compared with 2013 and 2014,the meteorological conditions in July 2015 were not more favorable for the diffusion of pollutants.
基金Supported by the Natural Science Foundation of China,No40475020Special Project of National Sci./Tech. Basic Research No 2006FY220300
文摘Based on the circumfluence situation of the out- and in-Tibet Plateau Vortex (TPV) from 1998-2004 and its weather-influencing system,multiple synthesized physical fields in the middle-upper troposphere of the out- and in-TPV are computationally analyzed by using re-analysis data from National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) of United States.Our research shows that the departure of TPV is caused by the mutual effects among the weather systems in Westerlies and in the subtropical area,within the middle and the upper troposphere.This paper describes the large-scale meteorological condition and the physics image of the departure of TPV,and the main differences among the large-scale conditions for all types of TPVs.This study could be used as the scientific basis for predicting the torrential rain and the floods caused by the TPV departure.
基金supported by the National Natural Science Foundation of China(Grant Nos.42088101 and 42175069)the National Key R&D Program of China(Grant No.2018YFC1505602).
文摘It is still not well understood if subseasonal variability of the local PM_(2.5) in the Beijing-Tianjin-Hebei(BTH)region is affected by the stratospheric state.Using PM_(2.5) observations and the ERA5 reanalysis,the evolution of the air quality in BTH during the January 2021 sudden stratospheric warming(SSW)is explored.The subseasonal variability of the PM_(2.5) concentration after the SSW onset is evidently enhanced.Stratospheric circumpolar easterly anomalies lasted for 53 days during the January-February 2021 SSW with two evident stratospheric pulses arriving at the ground.During the tropospheric wave weakening period and the intermittent period of dormant stratospheric pulses,the East Asian winter monsoon weakened,anomalous temperature inversion developed in the lower troposphere,anomalous surface southerlies prevailed,atmospheric moisture increased,and the boundary layer top height lowered,all of which favor the accumulation of pollutant particulates,leading to two periods of pollution processes in the BTH region.In the phase of strengthened East Asian winter monsoon around the very beginning of the SSW and another two periods when stratospheric pulses had reached the near surface,opposite-signed circulation patterns and meteorological conditions were observed,which helped to dilute and diffuse air pollutants in the BTH region.As a result,the air quality was excellent during the two periods when the stratospheric pulse had reached the near surface.The increased subseasonal variation of the regional pollutant particulates after the SSW onset highlights the important role of the stratosphere in the regional environment and provides implications for the environmental prediction.
基金Supported by the Project for Key Technology Integration and Application of China Meteorological Administration(CMAGJ2013M74)Special Project for Forecasters of China Meteorological Administration(CMAYBY2015-039)Special Project for Forecasters of Jiangxi Meteorological Bureau"Comparative Analysis of Mesoscale Characteristics during Two Typhoon Rainstorm Processes"。
文摘The causes of persistent haze pollution in Jiujiang City from the end of November to the beginning of December 2016 are analyzed. The results show that there were three main long-distance paths to transport fine particles to Jiujiang. The upstream guide wind and the local static weather conditions made local pollutants superimposed on the particulate matter. The first source emission and two conversion of different inorganic pollutants contributed to the increase in the concentration of particles in Jiujiang. High temperature and high humidity could promote the formation of two organic particles. But when temperature was low in winter,the increase of energy consumption made local source emission increase. The high molecular weight semi-volatile organic compounds in the air were adsorbed on the surface of the particles,and the haze was gradually formed through the process of hygroscopic growth and the aging of particles. Jiujiang's natural landform,the " valley wind" circulation effect of dominant wind,and the radiation effect of aerosol were favorable for the accumulation of pollutants in Jiujiang.
基金Science and Technology Open Research Fund of Guizhou Meteorological Bureau(KF[2009]08).
文摘According to the air quality monitoring and meteorological observation data from 2015 to 2020,the air pollution characteristics and causes were analyzed in the Ghost Festival(on the 15 th of the 7 th lunar month)for the main urban area of Liupanshui City in western Guizhou Province.The results showed that air pollution to different extent occurred in the Ghost Festival every year,reaching the level of heavy pollution in half of the year.The pollution time is generally from 21:00 on the day to 01:00 on the next day.The pollutants mainly come from the smoke dust generated by people burning sacrificial offerings and industrial pollution of iron and steel manufacturing under adverse weather conditions.The primary pollutant is PM 2.5,and the annual variation of pollution shows a downward trend.Precipitation weather is in the majority,which is favorable for reducing the pollution degree;the relationship between wind direction,wind speed and pollution degree is closed;the atmospheric inversion is weak,which has no obvious influence on the change of air pollution;the relative humidity is high,which is conducive to the formation and maintenance of pollution;there is a very significant negative correlation between the degree of air pollution and wind energy,and significantly negative correlation between the degree of air pollution and atmospheric turbulence intensity.Advocating civilized sacrifice and strengthening management is beneficial to reducing the degree of pollution.This paper can be used as a reference for air quality forecasts and taking the appropriate measures to reduce pollution.
文摘This study mainly introduces a large-scale heavy haze weather process in northern China from November 11 to 17, 2020, and analyzes the weather process. Methods such as comparative analysis and data analysis were used in this study. The main reasons for the formation of smog are as follows. First, the relative humidity is high and the water vapor content is relatively high. Second, the atmosphere is in a static and stable state, and suspended particulate matter in the atmosphere is not easy to diffuse and dilute, so it will gradually accumulate in urban areas and suburban areas. Third, there is a temperature inversion in the vertical direction, and the suspended particles in the air are difficult to drift to high altitudes and are blocked at low altitudes and near the ground. Fourth, there must be cooling conditions. Meteorological factors are the external causes for the formation of smog. And inversion intensity has a negative correlation with visibility, which has some indicating importance in fog and haze predictions. Large-scale haze weather mainly occurs in the large-scale atmospheric circulation with weak cold air and good water vapor conditions, and wind near the ground is small. Due to the high humidity in haze weather, fog droplets provide adsorption and reaction sites, accelerating the conversion of gaseous pollutants to liquid particles. At the same time, particles are also easy to act as condensation nucleus to accelerate the generation of haze. When the two interact, the pollutants are not easy to diffuse outward, resulting in agglomeration effect, and the pollution is getting heavier.
文摘The article is devoted to the discussion of the advantages of assessing the environmental comfort of the climate,based on the natural features of the climate and the bioclimatic conditions of the territory.The study assessed the ecological comfort of the climate in the city of Taganrog on the basis of the developed original sequence of performing three stages of assessing the totality of bioclimatic indicators with the final calculation of the values of the integral indicator of the bioclimatic comfort of the climate.The results of the assessment showed,according to the average long-term climatic data,the presence of sub-comfortable climates with a tendency to transition to comfortable climate conditions in the warm period of the year.The cold season was distinguished by uncomfortable conditions according to long-term average climatic data.Modeling calculations of the possible risk to the health of city residents in the presence of concentrations of suspended solids in the surface air layer,together with carbon monoxide,exceeding the maximum one-time values by more than 7 times,showed that the development of possible resorptive or carcinogenic effects in these circumstances will occur in 1/3 the population of the city.The prospects for the assessment of the ecological comfort of the climate,which allow in the future to adequately calculate the magnitude of environmental risks to public health caused by pollution of the surface air layer,are shown.
基金supported by the National Natural Science Foundation of China(Grant Nos.11873081 and 11603065)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China and administered by the Chinese Academy of Sciences。
文摘Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions,one of the associated basic tasks.As one of three potential sites to host the 12-meter Large Optical/infrared Telescope(LOT),the Muztagh-ata site,which is located on the Pamir Plateau in Xinjiang,in west China,began its site-testing task in the spring of 2017.In this paper,we firstly start with an introduction to the site and then present a statistical analysis of the ground-level meteorological properties such as air temperature,barometric pressure,relative humidity,and wind speed and direction,recorded by an automatic weather station with standard meteorological sensors for a two-year duration.We also show the monitoring results of sky brightness during this period.
基金supported by a grant from the National Key R&D Plan(Quantitative Relationship and Regulation Principle between Regional Oxidation Capacity of Atmospheric and Air Quality 2017YFC0210003)the National Natural Science Foundation of China(No.41505133&41775162)+1 种基金the National Research Program for Key Issues in Air Pollution Control(DQGG0101)the Beijing Major Science and Technology Project 510(No.Z181100005418014)。
文摘An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017.73 out of 96 selected cities,most located in the Beijing-TianjinHebei and the surrounding area(BTHS),suffered severe ozone pollution.A north-south contrast ozone distribution,with higher ozone(199±33μg/m3)in the BTHS and lower ozone(118±25μg/m^3)in the Yangtze River Delta(YRD),was found to be dominated by the position of the West Pacific Subtropical High(WPSH)and mid-high latitude wave activities.In the BTHS,the positive anomalies of geopotential height at 500 hPa and temperature at the surface indicated favorable meteorological conditions for local ozone formation.Prevailing northwesterly winds in the mid-high troposphere and warm advection induced by weak southerly winds in the low troposphere resulted in low-moderate relative humidity(RH),less total cloud cover(TGC),strong solar radiation and high temperatures.Moreover,southerly winds prevailing over the BTHS aggravated the pollution due to regional transportation of O3 and its precursors.On one hand,the deep sinking motion and inversion layer suppressed the dispersion of pollutants.On the other hand,O3-rich air in the upper layer was maintained at night due to temperature inversion,which facilitated O3 vertical transport to the surface in the next-day morning due to elevated convection.Generally,temperature,UV radiation,and RH showed good correlations with O3 in the BTHS,with rates of 8.51(μg/m^3)/℃(within the temperature range of 20-38℃),59.54(μg/m^3)/(MJ/m^2)and-1.93(μg/m^3)/%,respectively.
文摘An upswing in haze weather during autumn and winter has been observed over North and Northeast China in recent years, imposing adverse impacts upon local socioeconomic development and human health. However, such an increase in the occurrence of haze events and its association with natural climate variability and climate change are not well understood. To investigate the climatology of the meteorological factors associated with haze events and their natural variability, this study uses a meteorological pollution index called PLAM(Parameter Linking Air-quality to Meteorological conditions) and ERA-Interim reanalysis data. The results suggest that high PLAM values tend to occur over southern parts of northern China, implying the weather conditions over this area are favorable for the occurrence of haze weather. For the period 1979–2014, the regional mean PLAM shows an overall increase across Beijing, Tianjin, and Hebei Province, and parts of Shanxi Province. Also, a periodicity of 28–34 months is found in the temporal variation of PLAM, which implies a potential association of PLAM with the stratospheric Quasi-Biannual Oscillation(QBO). By using the QBO index during the autumn and winter seasons in the preceding year, an increase in PLAM is found for the westerly phases of the QBO, relative to the easterly phases. An upper-tropospheric warming is also found in the westerly phases, which can induce a stable stratification that favors the increase in PLAM across the midlatitudes. The modulations of large-scale environmental factors, including moist static stability,vertical velocity, and temperature advection, also act to enhance PLAM in the westerly phases. However, the baroclinic term of moist potential vorticity at 700 hPa tends to decrease over the south, and an increase in low-level ascent is found over the north. These factors can reduce PLAM and possibly limit the statistical significance of the increased PLAM in the westerly phases of the QBO.
