An analysis of the changes in vegetation cover on the territory of the Republic of Khakassia in 2000–2021 due to climatic trends was carried out based on the MODIS data.The changes in vegetation cover were estimated ...An analysis of the changes in vegetation cover on the territory of the Republic of Khakassia in 2000–2021 due to climatic trends was carried out based on the MODIS data.The changes in vegetation cover were estimated based on trends in Normalized Difference Vegetation Index(NDVI)and Enhanced Vegetation Index(EVI).In general,in the 21st century,an increase in the biomass of vegetation cover is observed.Positive trends were observed in 16%–22%of the territory,and negative only in 1%–3%.For about 20%of the analyzed territory,a significant influence of climate on the changes in vegetation cover was revealed.The most pronounced negative impact on vegetation cover was caused by summer air and soil temperatures,spring temperature,and summer winds,and the positive impact was caused by summer precipitation and soil moisture.The response of the vegetation cover to climate was non-uniform concerning the topography.Thus,a significant correlation with the amount of precipitation was observed for~20%–35%of vegetation growing below 600 m above sea level and for less than 5%above this elevation.The negative effect of summer temperatures on plants prevailed mainly at an elevation below~1400 m above sea level.Projected climate change is likely to lead to significant degradation of vegetation in the steppe and foreststeppe in Khakassia in the coming decades.展开更多
The study focused on the detection of indicators of climate change in 24-hourly annual maximum series (AMS) rainfall data collected for 36 years (1982-2017) for Warri Township, using different statistical methods yiel...The study focused on the detection of indicators of climate change in 24-hourly annual maximum series (AMS) rainfall data collected for 36 years (1982-2017) for Warri Township, using different statistical methods yielded a statistically insignificant positive mild trend. The IMD and MCIMD downscaled model’s time series data respectively produced MK statistics varying from 1.403 to 1.4729, and 1.403 to 1.463 which were less than the critical Z-value of 1.96. Also, the slope magnitude obtained showed a mild increasing trend in variation from 0.0189 to 0.3713, and 0.0175 to 0.5426, with the rate of change in rainfall intensity at 24 hours duration as 0.4536 and 0.42 mm/hr.year (4.536 and 4.2 mm/decade) for the IMD and the MCIMD time series data, respectively. The trend change point date occurred in the year 2000 from the distribution-free CUSUM test with the trend maintaining a significant and steady increase from 2010 to 2015. Thus, this study established the existence of a trend, which is an indication of a changing climate, and satisfied the condition for rainfall Non-stationary intensity-duration-frequency (NS-IDF) modeling required for infrastructural design for combating flooding events.展开更多
The recognition on the trend of wind energy stability is still extremely rare,although it is closely related to acquisition efficiency,grid connection,equipment lifetime,and costs of wind energy utilization.Using the ...The recognition on the trend of wind energy stability is still extremely rare,although it is closely related to acquisition efficiency,grid connection,equipment lifetime,and costs of wind energy utilization.Using the 40-year(1979–2018)ERA-Interim data from the European Center for Medium-Range Weather Forecasts,this study presented the spatial-temporal distribution and climatic trend of the stability of global offshore wind energy as well as the abrupt phenomenon of wind energy stability in key regions over the past 40 years with the climatic analysis method and Mann-Kendall(M-K)test.The results show the following 5 points.(1)According to the coefficient of variation(C_(v))of the wind power density,there are six permanent stable zones of global offshore wind energy:the southeast and northeast trade wind zones in the Indian,Pacific and Atlantic oceans,the Southern Hemisphere westerly,and a semi-permanent stable zone(North Indian Ocean).(2)There are six lowvalue zones for both seasonal variability index(S_(v))and monthly variability index(M_(v))globally,with a similar spatial distribution as that of the six permanent stable zones.M_(v) and S_(v) in the Arabian Sea are the highest in the world.(3)After C_(v),M_(v) and S_(v) are comprehensively considered,the six permanent stable zones have an obvious advantage in the stability of wind energy over other sea areas,with C_(v) below 0.8,M_(v) within 1.0,and S_(v) within 0.7 all the year round.(4)The global stability of offshore wind energy shows a positive climatic trend for the past four decades.C_(v),M_(v) and S_(v) have not changed significantly or decreased in most of the global ocean during 1979 to2018.That is,wind energy is flat or more stable,while the monthly and seasonal variabilities tend to shrink/smooth,which is beneficial for wind energy utilization.(5)C_(v) in the low-latitude Pacific and M_(v) and S_(v) in both the North Indian Ocean and the low-latitude Pacific have an obvious abrupt phenomenon at the end of the20th century.展开更多
Understanding temperature variability especially elevation dependent warming(EDW)in high-elevation mountain regions is critical for assessing the impacts of climate change on water resources including glacier melt,deg...Understanding temperature variability especially elevation dependent warming(EDW)in high-elevation mountain regions is critical for assessing the impacts of climate change on water resources including glacier melt,degradation of soils,and active layer thickness.EDW means that temperature is warming faster with the increase of altitude.In this study,we used observed temperature data during 1979-2017 from 23 meteorological stations in the Qilian Mountains(QLM)to analyze temperature trend with Mann-Kendall(MK)test and Sen’s slope approach.Results showed that the warming trends for the annual temperature followed the order of T_min>T_mean>T_max and with a shift both occurred in 1997.Spring and summer temperature have a higher increasing trend than that in autumn and winter.T_mean shifts occurred in 1996 for spring and summer,in 1997 for autumn and winter.T_max shifts occurred in 1997 for spring and 1996 for summer.T_min shifts occurred in 1997 for spring,summer and winter as well as in 1999 for autumn.Annual mean diurnal temperature range(DTR)shows a significant decreasing trend(-0.18°C/10a)from 1979 to 2017.Summer mean DTR shows a significant decreasing trend(-0.26°C/10a)from 1979 to 2017 with a shift occurred in 2010.After removing longitude and latitude factors,we can learn that the warming enhancement rate of average annual temperature is 0.0673°C/km/10a,indicating that the temperature warming trend is accelerating with the continuous increase of altitude.The increase rate of elevation temperature is 0.0371°C/km/10a in spring,0.0457°C/km/10a in summer,0.0707°C/km/10a in autumn,and 0.0606°C/km/10a in winter,which indicates that there is a clear EDW in the QLM.The main causes of warming in the Qilian Mountains are human activities,cloudiness,ice-snow feedback and El Nino phenomenon.展开更多
In this study, the trends of upper-air temperatures are analysed by utilising radiosonde observations for the barometric levels at 700, 500, 300, 200, 150, 100 and 50 hPa from five meteorological stations within the A...In this study, the trends of upper-air temperatures are analysed by utilising radiosonde observations for the barometric levels at 700, 500, 300, 200, 150, 100 and 50 hPa from five meteorological stations within the Arabian Peninsula from January 1986 to August 2015. The mean monthly variations of the temperatures at these levels are characterised and established. The magnitudes of the annual trends of the mean temperatures for each site for the selected barometric levels are studied and statistically tested using Mann-Kendall rank statistics at different significance levels. The temperature trends at different pressure levels show that the upper troposphere and lower stratosphere are warming, while the middle troposphere is cooling which is consistent with the findings of other studies. The variations in upper air temperature observed in this study can be attributed to a range of factors, including increasing greenhouse gas concentrations, changes in atmospheric circulation patterns, variations in solar activity, aerosols and volcanic eruptions, and land use and land cover change.展开更多
Rainfall and temperature are climatic variables mostly affected by global warming. This study aimed to investigate the temporal trend analysis in annual temperature and rainfall in the Southern Togo for the 1970-2014 ...Rainfall and temperature are climatic variables mostly affected by global warming. This study aimed to investigate the temporal trend analysis in annual temperature and rainfall in the Southern Togo for the 1970-2014 period. Daily and annual rainfall and temperature were collected from four weather stations at Atakpame, Kouma-Konda, Lome, and Tabligbo. The temperature variability was determined by the Standardized Anomaly Index (SAI) and the annual rainfall variability was determined using the Standardized Precipitation Index (SPI). The Mann-Kendall test was used for trend analysis. Mann-Kendall statistical test for the mean annual, mean annual minimum and maximum temperature from 1970 to 2014 showed significant warming trends for all stations except Kouma-Konda where mean annual maximum temperature had exhibited non significant cooling trend (P = 0.01). For Standardized Precipitation Index in the 12-month time scale, dry tendency dominates Atakpamé (55.7%) and Kouma-Konda (55.5%) while wet tendency dominates slightly Lomé (50.9%) and Tabligbo (51.4%). The Mann-Kendall test revealed an increasing trend in standardized anomaly index at all the sites, prejudicial to rainfed agriculture practiced by about 90% of Togolese crop growers. The trend analysis in the climate variables indicated a change in climate that necessitates some specific actions for resources management sustainability and conservation.展开更多
In this paper, the impacts of climate change on development rate and production of corn in the northeastern China are discussed. The results show that the higher the temperature is, the faster the development rate wil...In this paper, the impacts of climate change on development rate and production of corn in the northeastern China are discussed. The results show that the higher the temperature is, the faster the development rate will be. And the more the precipitation is, the slower the development rate will be. Of which, air temperature is the controlling factor of corn development rate. The influences of development rate on corn yield are remarkable. The impacts of development rate on production in first and last periods are great, and small in the middle two periods. The development rate is positive by relate with corn production from sowing to emergence stage and negative during other periods. So, it is very important to arrange a suitable sowing time for com cultivating in the northeastern China.展开更多
In the context of climate change, the frequency and intensity of extreme events such as floods and droughts will increase which could put tremendous challenges in water resources management in the coming days. While s...In the context of climate change, the frequency and intensity of extreme events such as floods and droughts will increase which could put tremendous challenges in water resources management in the coming days. While scientific knowledge on climate threats and changing climate patterns are essential, it is also important to consider the impacts in relation to how the threats are perceived and handled by local people. This paper intends to assess the trend and people’s perception on temperature and precipitation. Three focus groups’ discussion and a total number of 240 households were interviewed during field visit. The collected information was scaled from the least preferred-1 to the most preferred-5 based on their preferences. The trend of mean of annual average, maximum and minimum temperature indicates that the temperature has increased significantly and precipitation intensity and magnitude are also in increasing trend in the monsoon and postmonsoon seasons which may raise the extreme flood events. These facts were verified with the people’s perception. This finding could be useful for formulation of effective flood management policy and plan in this river basin as well as very applicable for other similar areas.展开更多
Background:The first three censuses of the 50-ha plot at Barro Colorado Island spanned an unusually harsh dry season during the 1983 El Nino.By the early 1990 s,we had documented increases in tree mortality,tree growt...Background:The first three censuses of the 50-ha plot at Barro Colorado Island spanned an unusually harsh dry season during the 1983 El Nino.By the early 1990 s,we had documented increases in tree mortality,tree growth,and large population fluctuations of many species during the 1982-1985 census interval.At the time,we asserted that increasing drought frequency would greatly affect the forest.With the benefit of five more censuses at Barro Colorado from 1995-2015,we can now put the 1980 conditions in a longer perspective and test the hypothesis that increasing droughtiness has continued to change the forest.Methods:A 50-ha forest plot on Barro Colorado Island was censused eight times,in 1982 and every five years since1985.All free-standing woody stems were measured,mapped,and identified In each census.Results:1) The period 1982-1992 included several extreme dry seasons,not just 1983,but since then there have been few such droughts.2) Dbh growth declined from a peak in the early 1980 s to its lowest in the early 1990 s.From 1995-2015 it increased slightly,but not returning to the initial peak.Nearly every species and all dbh categories followed the same pattern.3) The elevated stand-wide mortality rate of large trees during the 1982-1985 drought has not returned,and most individual species showed the same pattern of elevated mortality in the 1980 s followed by low and fairly stable mortality after 1990.4) Sapling mortality declined after 1985,but rose again in the late-90 s,so the 1980 s drought period no longer looks unusual.Mortality of individual species' saplings fluctuated erratically,including cases where mortality during the drought was lower than after.5) Population sizes of individual species fluctuated in all possible directions.Some species declined precipitously during the drought,then recovered,but others did not recover.Other species increased in abundance during the drought.Conclusions:Droughts of the 1980 s elevated tree growth and mortality at Barro Colorado,but since 1990,demographic rates have remained lower,paralleling a moderate climate with few severe droughts after 1990.Moisture-demanding species suffered during the drought,but many have since recovered.We do not know how often such drought periods recur.Moreover,many species' abundances fluctuated over 35 years with no known cause.展开更多
The authors exploit the remarkable connection between the Chinese climate trends and the annular modes by partitioning the trends into components linearly congruent with and linearly independent of the annular modes. ...The authors exploit the remarkable connection between the Chinese climate trends and the annular modes by partitioning the trends into components linearly congruent with and linearly independent of the annular modes. Results show that the winter hemisphere annular mode has closer connection to Chinese climate than the summer one, e.g., the wetting JJA (June-July-August) rainfall trend along the Yangtze River valley and the associated temperature trends are significantly linearly congruent with the trend of the southern annular mode, while the JFM (January-February-March) climate trends are closely linked to the northern annular mode. The seasonal differences of a meridional wave-train-like chain across the equatorial Pacific associated with the annular modes are responsible for the seasonal-dependent connections to Chinese climate.展开更多
The authors examine the effects of external forcing agents such as greenhouse gases (GHGs) and aerosols, as well as solar variability and ozone, on global land monsoon precipitation by using a coupled climate model Ha...The authors examine the effects of external forcing agents such as greenhouse gases (GHGs) and aerosols, as well as solar variability and ozone, on global land monsoon precipitation by using a coupled climate model HadGEM1, which was developed by the Met Office Hadley Centre for Climate Research. The results indicate that HadGEM1 performs well in simulating the observed decreasing trend of global land monsoon precipitation over the past 50 years. This trend mainly occurred in the Northern Hemisphere and is significantly different from the trend of natural variability due to ocean-atmosphere-land interactions. The coherence between the simulation and the observations indicates that the specified external forcing agents, including GHGs and aerosols as well as solar variability and ozone, are important factors that have affected the decreasing trend of global land monsoon precipitation in the past 50 years.展开更多
Linhe National Meteorological Station, a representative weather station in the Hetao Irrigation District of China, was selected as the research site for the present study. Changes in climatic variables and reference e...Linhe National Meteorological Station, a representative weather station in the Hetao Irrigation District of China, was selected as the research site for the present study. Changes in climatic variables and reference evapotranspiration(ET_0)(estimated by the Penman-Monteith method) were detected using Mann-Kendall tests and Sen's slope estimator, respectively. The authors analyzed the relationship between the ET_0 change and each climatic variable's change. From 1954 to 2012, the air temperature showed a significant increasing trend, whereas relative humidity and wind speed decreased dramatically. These changes resulted in a slight increase in ET_0. The radiative component of total ET_0 increased from 50% to 57%, indicating that this component made a greater contribution to the increase in total ET_0 than the aerodynamic component, especially during the crop growing season(from April to October). The sensitivity analysis showed that ET_0 in Hetao is most sensitive to mean daily air temperature(11.8%), followed by wind speed(-7.3%) and relative humidity(4.8%). Changes in sunshine duration had only a minor effect on ET_0 over the past 59 years.展开更多
This paper has organized and summarized the economic analysis on climate change from five angles,namely,connotation of discount rate,identification of and dispute about discount rate,discounting way,impact of the disc...This paper has organized and summarized the economic analysis on climate change from five angles,namely,connotation of discount rate,identification of and dispute about discount rate,discounting way,impact of the discount rate,and the integrated evaluation model of climate change impact and the discount evaluation.As the climate change economic analysis shows,there is a major dispute about discount rate between the market school and the ethic school.Rate of discount largely relates to the present value of potential loss attributable to climate change,and then influences the selection of policies for adapting and slowing down climate change.In the past,the constant index discount was adopted as the main way.But with the full understanding of discount rate,the uncertainty of loss attributable to climate change has been considered in the discount.展开更多
In this study,the ability of dynamical downscaling for reduction of artificial climate trends in global reanalysis is tested in China.Dynamical downscaling is performed using a 60-km horizontal resolution Regional Int...In this study,the ability of dynamical downscaling for reduction of artificial climate trends in global reanalysis is tested in China.Dynamical downscaling is performed using a 60-km horizontal resolution Regional Integrated Environmental Model System (RIEMS) forced by the NCEP-Department of Energy (DOE) reanalysis II (NCEP-2).The results show that this regional climate model (RCM) can not only produce dynamically consistent fine scale fields of atmosphere and land surface in the regional domain,but it also has the ability to minimize artificial climate trends existing in the global reanalysis to a certain extent.As compared to the observed 2-meter temperature anomaly averaged across China,our model can simulate the observed inter-annual variation and variability as well as reduce artificial climate trends in the reanalysis by approximately 0.10 C decade 1 from 1980 to 2007.The RIEMS can effectively reduce artificial trends in global reanalysis for areas in western China,especially for regions with high altitude mountains and deserts,as well as introduce some new spurious changes in other local regions.The model simulations overestimated observed winter trends for most areas in eastern China with the exception of the Tibetan Plateau,and it greatly overestimated observed summer trends in the Sichuan Basin located in southwest China.This implies that the dynamical downscaling of RCM for long-term trends has certain seasonal and regional dependencies due to imperfect physical processes and parameterizations.展开更多
Identifying the Northern Hemisphere (NH) temperature reconstruction and instrumental data forthe past 1000 years shows that climate change in the last millennium includes long-term trends and variousoscillations. Two ...Identifying the Northern Hemisphere (NH) temperature reconstruction and instrumental data forthe past 1000 years shows that climate change in the last millennium includes long-term trends and variousoscillations. Two long-term trends and the quasi-70-year oscillation were detected in the global temperatureseries for the last 140 years and the NH millennium series. One important feature was emphasized thattemperature decreases slowly but it increases rapidly based on the analysis of different series. Benefits can beobtained of climate change from understanding various long-term trends and oscillations. Millennial temperatureproxies from the natural climate system and time series of nonlinear model system are used in understanding thenatural climate change and recognizing potential benefits by using the method of wavelet transform analysis. Theresults from numerical modeling show that major oscillations contained in numerical solutions on theinterdecadal timescale are consistent with that of natural proxies. It seems that these oscillations in the climatechange are not directly linked with the solar radiation as an external forcing. This investigation may concludethat the climate variability at the interdecadal timescale strongly depends on the internal nonlinear effects in theclimate system.展开更多
Alps are an important geographical area of the European continent and,in this area,temperature increase is most evident.However,the 1991-2020 climate normal in the Alps has still not been thoroughly investigated.Aimin...Alps are an important geographical area of the European continent and,in this area,temperature increase is most evident.However,the 1991-2020 climate normal in the Alps has still not been thoroughly investigated.Aiming to fill this gap with a focus on high-elevation environments,minimum and maximum daily air temperature acquired by 23 automatic weather station were used.The results show that the mean annual values of minimum and maximum temperature for the 1991-2020 climate normal in the Alps are-2.4℃ and 4.4℃,respectively,with a warming rate of 0.5℃/10 years.The mean annual temperature comparison between 1961-1990 and 1971-2000,1961-1990 and 1981-2010,1961-1990 and 1991-2020 climate normal show an increase of 0.3℃,0.5℃ and 0.9℃,respectively.The results also confirm that seasonal and annual temperatures are rising through the whole Alpine arc,mainly in summer and autumn.This work highlights that annual minimum and maximum temperature do not seem to be affected by a positive elevation-dependent warming.Instead,a positive elevation-dependent warming in the maximum values of the annual minimum temperature was found.If anthropogenic emissions maintain the trend of the last decades,the expected mean annual temperature of the 2001-2030 climate normal is-0.2℃,with an increase of 0.5℃ if compared to the 1991-2020 climate normal and with an increase of 1.5℃ if compared to the 1961-1990 climate normal.This study highlights the warming rate that is now present in the European Alps,provides indications on the warming rate that will occur in the coming years and highlights the importance of carrying out investigations that consider not only the last 30-year climate normal,but also the most recent 30-year climate normal by comparing them with each other.展开更多
Groundwater is reported to account for 87% of all drinking water resources in Dhaka which has suffered a decline of up to 75 m in some specific location. Over-extraction of groundwater is an extensive social problem i...Groundwater is reported to account for 87% of all drinking water resources in Dhaka which has suffered a decline of up to 75 m in some specific location. Over-extraction of groundwater is an extensive social problem in Dhaka and Gazipur city which needs to be investigating thoroughly. This study presents the diagnosis of groundwater depletion pattern and the yearly rate of decline over the last three decades for Dhaka and Gazipur metropolitan area. Groundwater data were collected from the relevant institutions in order to analyse the trend line and the rate of decline of groundwater levels for more than 30 years period to understand the long-time variability. Ten individual stations datasets for GWL have been analyzed for Dhaka and Gazipur within a selected reference time period (1980-2012). The highest depleted GWL were found in the Mirpur station which is now 68 m below ground. To find out the time span when the depletion rate is highest, the rate of decline of all datasets has been computed which shows that 1998-2005 is the consecutive eight years time span with the fastest depletion rate. On the other hand, the annual trend-line analysis shows rapid depletion pattern after the year 2000.展开更多
Trends in 20 extreme indices of temperature and precipitation are examined for Sri Lanka using high-quality datasets for 19 meteorological stations, for a period between 1980 and 2015. It is evident that annually aver...Trends in 20 extreme indices of temperature and precipitation are examined for Sri Lanka using high-quality datasets for 19 meteorological stations, for a period between 1980 and 2015. It is evident that annually averaged mean minimum temperatures are increasing across most of Sri Lanka. The difference between maximum and minimum temperatures, diurnal temperature range is decreasing, indicating that the minimum temperature is increasing faster than the maximum temperature. Significant decrease in the annual occurrence of cold nights and increase in the annual occurrence of warm nights are also obvious. When compared with temperature changes, less spatially coherent pattern of change and a lower level of statistical significance were observed in precipitation indices. The annual total precipitation (PRCPTOT) has indicated a significant increasing over 1980-2015. More than 80% of stations showed an increasing trend in precipitation indices. The trends in extreme precipitation events such as maximum one-day precipitation, maximum five-day precipitation, and total precipitation on extreme rainfall days (R95p and R99p) are increasing at most locations, indicating that the intensity of the rainfall is increasing. Increase of precipitation extreme trends indicates that occurrence of extreme rainfall events notably influences total annual precipitation in Sri Lanka. Therefore, the observed increases in total rainfall observed in many locations may be due in part to an increase in of extreme rainfall events. Patterns of change in precipitation extremes are more heavily influencing the climate variability by aggravating the variability, significantly influencing climate sensitive sectors such as agriculture and water resource management.展开更多
Despite the extreme events impact on various climate events frequency and intensity in many developing countries, there has been dearth information on daily climate trends and climatic extremes. This study comes to ch...Despite the extreme events impact on various climate events frequency and intensity in many developing countries, there has been dearth information on daily climate trends and climatic extremes. This study comes to characterize the climate type and its evolution in Morocco, specially the two regions Beni Mellal-Khenifra and Daraa-Tafilalt. RClimdex software has been used to calculate pluvio-thermal and ombro-thermic indices in the studied stations to reveal climate type in the two regions, their evolutions, and the daily extreme temperatures and precipitations. A cartographic representation has been done for the calculated indices and climatic trends in the stations from 1970 to 2016. As results, the temperature trend for hot day’s number shows a significant increase, while the cold night’s numbers, warm sequences, and precipitation are gradually decreases especially at Khouribga and Midelt. These observed modifications influence negatively the annual rainfall total in the year, the consecutive wet days, the maximums rainy days, and the increase of consecutively dry days. As a conclusion, the Martonne aridity and ombro-thermic indices, show that the temperatures and precipitations evolutions do not induce a change in the climate type for the studied regions.展开更多
基金supported by a grant from the Russian Science Foundation(No.22-17-20012)(https://rscf.ru/project/22-17-20012)with equal financial support from the Government of the Republic of Khakassia。
文摘An analysis of the changes in vegetation cover on the territory of the Republic of Khakassia in 2000–2021 due to climatic trends was carried out based on the MODIS data.The changes in vegetation cover were estimated based on trends in Normalized Difference Vegetation Index(NDVI)and Enhanced Vegetation Index(EVI).In general,in the 21st century,an increase in the biomass of vegetation cover is observed.Positive trends were observed in 16%–22%of the territory,and negative only in 1%–3%.For about 20%of the analyzed territory,a significant influence of climate on the changes in vegetation cover was revealed.The most pronounced negative impact on vegetation cover was caused by summer air and soil temperatures,spring temperature,and summer winds,and the positive impact was caused by summer precipitation and soil moisture.The response of the vegetation cover to climate was non-uniform concerning the topography.Thus,a significant correlation with the amount of precipitation was observed for~20%–35%of vegetation growing below 600 m above sea level and for less than 5%above this elevation.The negative effect of summer temperatures on plants prevailed mainly at an elevation below~1400 m above sea level.Projected climate change is likely to lead to significant degradation of vegetation in the steppe and foreststeppe in Khakassia in the coming decades.
文摘The study focused on the detection of indicators of climate change in 24-hourly annual maximum series (AMS) rainfall data collected for 36 years (1982-2017) for Warri Township, using different statistical methods yielded a statistically insignificant positive mild trend. The IMD and MCIMD downscaled model’s time series data respectively produced MK statistics varying from 1.403 to 1.4729, and 1.403 to 1.463 which were less than the critical Z-value of 1.96. Also, the slope magnitude obtained showed a mild increasing trend in variation from 0.0189 to 0.3713, and 0.0175 to 0.5426, with the rate of change in rainfall intensity at 24 hours duration as 0.4536 and 0.42 mm/hr.year (4.536 and 4.2 mm/decade) for the IMD and the MCIMD time series data, respectively. The trend change point date occurred in the year 2000 from the distribution-free CUSUM test with the trend maintaining a significant and steady increase from 2010 to 2015. Thus, this study established the existence of a trend, which is an indication of a changing climate, and satisfied the condition for rainfall Non-stationary intensity-duration-frequency (NS-IDF) modeling required for infrastructural design for combating flooding events.
基金The Open Fund Project of Shandong Provincial Key Laboratory of Ocean EngineeringOcean University of China under contract No.kloe201901the Open Research Fund of State Key Laboratory of Estuarine and Coastal Research under contract No.SKLEC-KF201707。
文摘The recognition on the trend of wind energy stability is still extremely rare,although it is closely related to acquisition efficiency,grid connection,equipment lifetime,and costs of wind energy utilization.Using the 40-year(1979–2018)ERA-Interim data from the European Center for Medium-Range Weather Forecasts,this study presented the spatial-temporal distribution and climatic trend of the stability of global offshore wind energy as well as the abrupt phenomenon of wind energy stability in key regions over the past 40 years with the climatic analysis method and Mann-Kendall(M-K)test.The results show the following 5 points.(1)According to the coefficient of variation(C_(v))of the wind power density,there are six permanent stable zones of global offshore wind energy:the southeast and northeast trade wind zones in the Indian,Pacific and Atlantic oceans,the Southern Hemisphere westerly,and a semi-permanent stable zone(North Indian Ocean).(2)There are six lowvalue zones for both seasonal variability index(S_(v))and monthly variability index(M_(v))globally,with a similar spatial distribution as that of the six permanent stable zones.M_(v) and S_(v) in the Arabian Sea are the highest in the world.(3)After C_(v),M_(v) and S_(v) are comprehensively considered,the six permanent stable zones have an obvious advantage in the stability of wind energy over other sea areas,with C_(v) below 0.8,M_(v) within 1.0,and S_(v) within 0.7 all the year round.(4)The global stability of offshore wind energy shows a positive climatic trend for the past four decades.C_(v),M_(v) and S_(v) have not changed significantly or decreased in most of the global ocean during 1979 to2018.That is,wind energy is flat or more stable,while the monthly and seasonal variabilities tend to shrink/smooth,which is beneficial for wind energy utilization.(5)C_(v) in the low-latitude Pacific and M_(v) and S_(v) in both the North Indian Ocean and the low-latitude Pacific have an obvious abrupt phenomenon at the end of the20th century.
基金financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23060301)the National Natural Science Foundation of China(No.41621001).
文摘Understanding temperature variability especially elevation dependent warming(EDW)in high-elevation mountain regions is critical for assessing the impacts of climate change on water resources including glacier melt,degradation of soils,and active layer thickness.EDW means that temperature is warming faster with the increase of altitude.In this study,we used observed temperature data during 1979-2017 from 23 meteorological stations in the Qilian Mountains(QLM)to analyze temperature trend with Mann-Kendall(MK)test and Sen’s slope approach.Results showed that the warming trends for the annual temperature followed the order of T_min>T_mean>T_max and with a shift both occurred in 1997.Spring and summer temperature have a higher increasing trend than that in autumn and winter.T_mean shifts occurred in 1996 for spring and summer,in 1997 for autumn and winter.T_max shifts occurred in 1997 for spring and 1996 for summer.T_min shifts occurred in 1997 for spring,summer and winter as well as in 1999 for autumn.Annual mean diurnal temperature range(DTR)shows a significant decreasing trend(-0.18°C/10a)from 1979 to 2017.Summer mean DTR shows a significant decreasing trend(-0.26°C/10a)from 1979 to 2017 with a shift occurred in 2010.After removing longitude and latitude factors,we can learn that the warming enhancement rate of average annual temperature is 0.0673°C/km/10a,indicating that the temperature warming trend is accelerating with the continuous increase of altitude.The increase rate of elevation temperature is 0.0371°C/km/10a in spring,0.0457°C/km/10a in summer,0.0707°C/km/10a in autumn,and 0.0606°C/km/10a in winter,which indicates that there is a clear EDW in the QLM.The main causes of warming in the Qilian Mountains are human activities,cloudiness,ice-snow feedback and El Nino phenomenon.
文摘In this study, the trends of upper-air temperatures are analysed by utilising radiosonde observations for the barometric levels at 700, 500, 300, 200, 150, 100 and 50 hPa from five meteorological stations within the Arabian Peninsula from January 1986 to August 2015. The mean monthly variations of the temperatures at these levels are characterised and established. The magnitudes of the annual trends of the mean temperatures for each site for the selected barometric levels are studied and statistically tested using Mann-Kendall rank statistics at different significance levels. The temperature trends at different pressure levels show that the upper troposphere and lower stratosphere are warming, while the middle troposphere is cooling which is consistent with the findings of other studies. The variations in upper air temperature observed in this study can be attributed to a range of factors, including increasing greenhouse gas concentrations, changes in atmospheric circulation patterns, variations in solar activity, aerosols and volcanic eruptions, and land use and land cover change.
文摘Rainfall and temperature are climatic variables mostly affected by global warming. This study aimed to investigate the temporal trend analysis in annual temperature and rainfall in the Southern Togo for the 1970-2014 period. Daily and annual rainfall and temperature were collected from four weather stations at Atakpame, Kouma-Konda, Lome, and Tabligbo. The temperature variability was determined by the Standardized Anomaly Index (SAI) and the annual rainfall variability was determined using the Standardized Precipitation Index (SPI). The Mann-Kendall test was used for trend analysis. Mann-Kendall statistical test for the mean annual, mean annual minimum and maximum temperature from 1970 to 2014 showed significant warming trends for all stations except Kouma-Konda where mean annual maximum temperature had exhibited non significant cooling trend (P = 0.01). For Standardized Precipitation Index in the 12-month time scale, dry tendency dominates Atakpamé (55.7%) and Kouma-Konda (55.5%) while wet tendency dominates slightly Lomé (50.9%) and Tabligbo (51.4%). The Mann-Kendall test revealed an increasing trend in standardized anomaly index at all the sites, prejudicial to rainfed agriculture practiced by about 90% of Togolese crop growers. The trend analysis in the climate variables indicated a change in climate that necessitates some specific actions for resources management sustainability and conservation.
文摘In this paper, the impacts of climate change on development rate and production of corn in the northeastern China are discussed. The results show that the higher the temperature is, the faster the development rate will be. And the more the precipitation is, the slower the development rate will be. Of which, air temperature is the controlling factor of corn development rate. The influences of development rate on corn yield are remarkable. The impacts of development rate on production in first and last periods are great, and small in the middle two periods. The development rate is positive by relate with corn production from sowing to emergence stage and negative during other periods. So, it is very important to arrange a suitable sowing time for com cultivating in the northeastern China.
文摘In the context of climate change, the frequency and intensity of extreme events such as floods and droughts will increase which could put tremendous challenges in water resources management in the coming days. While scientific knowledge on climate threats and changing climate patterns are essential, it is also important to consider the impacts in relation to how the threats are perceived and handled by local people. This paper intends to assess the trend and people’s perception on temperature and precipitation. Three focus groups’ discussion and a total number of 240 households were interviewed during field visit. The collected information was scaled from the least preferred-1 to the most preferred-5 based on their preferences. The trend of mean of annual average, maximum and minimum temperature indicates that the temperature has increased significantly and precipitation intensity and magnitude are also in increasing trend in the monsoon and postmonsoon seasons which may raise the extreme flood events. These facts were verified with the people’s perception. This finding could be useful for formulation of effective flood management policy and plan in this river basin as well as very applicable for other similar areas.
基金support of the U.S.National Science Foundation (awards 8206992,8906869,9405933,9909947,0948585 to S.P.Hubbell)the John D.and Catherine D.McArthur Foundationthe Smithsonian Tropical Research Institute
文摘Background:The first three censuses of the 50-ha plot at Barro Colorado Island spanned an unusually harsh dry season during the 1983 El Nino.By the early 1990 s,we had documented increases in tree mortality,tree growth,and large population fluctuations of many species during the 1982-1985 census interval.At the time,we asserted that increasing drought frequency would greatly affect the forest.With the benefit of five more censuses at Barro Colorado from 1995-2015,we can now put the 1980 conditions in a longer perspective and test the hypothesis that increasing droughtiness has continued to change the forest.Methods:A 50-ha forest plot on Barro Colorado Island was censused eight times,in 1982 and every five years since1985.All free-standing woody stems were measured,mapped,and identified In each census.Results:1) The period 1982-1992 included several extreme dry seasons,not just 1983,but since then there have been few such droughts.2) Dbh growth declined from a peak in the early 1980 s to its lowest in the early 1990 s.From 1995-2015 it increased slightly,but not returning to the initial peak.Nearly every species and all dbh categories followed the same pattern.3) The elevated stand-wide mortality rate of large trees during the 1982-1985 drought has not returned,and most individual species showed the same pattern of elevated mortality in the 1980 s followed by low and fairly stable mortality after 1990.4) Sapling mortality declined after 1985,but rose again in the late-90 s,so the 1980 s drought period no longer looks unusual.Mortality of individual species' saplings fluctuated erratically,including cases where mortality during the drought was lower than after.5) Population sizes of individual species fluctuated in all possible directions.Some species declined precipitously during the drought,then recovered,but others did not recover.Other species increased in abundance during the drought.Conclusions:Droughts of the 1980 s elevated tree growth and mortality at Barro Colorado,but since 1990,demographic rates have remained lower,paralleling a moderate climate with few severe droughts after 1990.Moisture-demanding species suffered during the drought,but many have since recovered.We do not know how often such drought periods recur.Moreover,many species' abundances fluctuated over 35 years with no known cause.
基金supported by the Major State Basic Research Development Program of China (973 Program) under grant No. 2005CB321703the National Natural Science Foundation of China under Grant Nos. 40523001, 40221503, and 40625014the China Meteorological Administration under Grant No. GYHY200706010
文摘The authors exploit the remarkable connection between the Chinese climate trends and the annular modes by partitioning the trends into components linearly congruent with and linearly independent of the annular modes. Results show that the winter hemisphere annular mode has closer connection to Chinese climate than the summer one, e.g., the wetting JJA (June-July-August) rainfall trend along the Yangtze River valley and the associated temperature trends are significantly linearly congruent with the trend of the southern annular mode, while the JFM (January-February-March) climate trends are closely linked to the northern annular mode. The seasonal differences of a meridional wave-train-like chain across the equatorial Pacific associated with the annular modes are responsible for the seasonal-dependent connections to Chinese climate.
基金supported by National Natural Science Foundation of China under GrantNos. 40625014, 40821092, and 90711004the National Basic Research Program of China (2006CB403603)the China Meteorological Administration (GYHY200706010,GYHY200706005)
文摘The authors examine the effects of external forcing agents such as greenhouse gases (GHGs) and aerosols, as well as solar variability and ozone, on global land monsoon precipitation by using a coupled climate model HadGEM1, which was developed by the Met Office Hadley Centre for Climate Research. The results indicate that HadGEM1 performs well in simulating the observed decreasing trend of global land monsoon precipitation over the past 50 years. This trend mainly occurred in the Northern Hemisphere and is significantly different from the trend of natural variability due to ocean-atmosphere-land interactions. The coherence between the simulation and the observations indicates that the specified external forcing agents, including GHGs and aerosols as well as solar variability and ozone, are important factors that have affected the decreasing trend of global land monsoon precipitation in the past 50 years.
基金supported by the National Natural Science Foundation of China(Grant No.51179005)the Special Fund for Public Welfare Industry of the Ministry of Water Resources of China(Grant No.201401036)
文摘Linhe National Meteorological Station, a representative weather station in the Hetao Irrigation District of China, was selected as the research site for the present study. Changes in climatic variables and reference evapotranspiration(ET_0)(estimated by the Penman-Monteith method) were detected using Mann-Kendall tests and Sen's slope estimator, respectively. The authors analyzed the relationship between the ET_0 change and each climatic variable's change. From 1954 to 2012, the air temperature showed a significant increasing trend, whereas relative humidity and wind speed decreased dramatically. These changes resulted in a slight increase in ET_0. The radiative component of total ET_0 increased from 50% to 57%, indicating that this component made a greater contribution to the increase in total ET_0 than the aerodynamic component, especially during the crop growing season(from April to October). The sensitivity analysis showed that ET_0 in Hetao is most sensitive to mean daily air temperature(11.8%), followed by wind speed(-7.3%) and relative humidity(4.8%). Changes in sunshine duration had only a minor effect on ET_0 over the past 59 years.
基金supported by NSFC National Outstanding Youth Science Foundation of China (Grant No.71103111)MOST Special Project of Innovative Methodology (Grant No.2012IM010300)Twelfth Five-Year National Science and Technology Support Program (Grant No.2012BAC20B01)
文摘This paper has organized and summarized the economic analysis on climate change from five angles,namely,connotation of discount rate,identification of and dispute about discount rate,discounting way,impact of the discount rate,and the integrated evaluation model of climate change impact and the discount evaluation.As the climate change economic analysis shows,there is a major dispute about discount rate between the market school and the ethic school.Rate of discount largely relates to the present value of potential loss attributable to climate change,and then influences the selection of policies for adapting and slowing down climate change.In the past,the constant index discount was adopted as the main way.But with the full understanding of discount rate,the uncertainty of loss attributable to climate change has been considered in the discount.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No. KGCX2-YW-356)the R & D Special Fund for Public Welfare Industry (Meteorology) (Grant No. GYHY201006023)the National Natural Science Foundation of China (Grant No.40805032)
文摘In this study,the ability of dynamical downscaling for reduction of artificial climate trends in global reanalysis is tested in China.Dynamical downscaling is performed using a 60-km horizontal resolution Regional Integrated Environmental Model System (RIEMS) forced by the NCEP-Department of Energy (DOE) reanalysis II (NCEP-2).The results show that this regional climate model (RCM) can not only produce dynamically consistent fine scale fields of atmosphere and land surface in the regional domain,but it also has the ability to minimize artificial climate trends existing in the global reanalysis to a certain extent.As compared to the observed 2-meter temperature anomaly averaged across China,our model can simulate the observed inter-annual variation and variability as well as reduce artificial climate trends in the reanalysis by approximately 0.10 C decade 1 from 1980 to 2007.The RIEMS can effectively reduce artificial trends in global reanalysis for areas in western China,especially for regions with high altitude mountains and deserts,as well as introduce some new spurious changes in other local regions.The model simulations overestimated observed winter trends for most areas in eastern China with the exception of the Tibetan Plateau,and it greatly overestimated observed summer trends in the Sichuan Basin located in southwest China.This implies that the dynamical downscaling of RCM for long-term trends has certain seasonal and regional dependencies due to imperfect physical processes and parameterizations.
基金National Natural Foundation of China (No.90502001), the doctoral project of the Ministry ofEducation of China and the State Key Development Program for Basic Research of China (2006CB400501)
文摘Identifying the Northern Hemisphere (NH) temperature reconstruction and instrumental data forthe past 1000 years shows that climate change in the last millennium includes long-term trends and variousoscillations. Two long-term trends and the quasi-70-year oscillation were detected in the global temperatureseries for the last 140 years and the NH millennium series. One important feature was emphasized thattemperature decreases slowly but it increases rapidly based on the analysis of different series. Benefits can beobtained of climate change from understanding various long-term trends and oscillations. Millennial temperatureproxies from the natural climate system and time series of nonlinear model system are used in understanding thenatural climate change and recognizing potential benefits by using the method of wavelet transform analysis. Theresults from numerical modeling show that major oscillations contained in numerical solutions on theinterdecadal timescale are consistent with that of natural proxies. It seems that these oscillations in the climatechange are not directly linked with the solar radiation as an external forcing. This investigation may concludethat the climate variability at the interdecadal timescale strongly depends on the internal nonlinear effects in theclimate system.
基金the framework of the Gio Mon Project,co-financed by“Fondazione Cassa di Risparmio di Torino”。
文摘Alps are an important geographical area of the European continent and,in this area,temperature increase is most evident.However,the 1991-2020 climate normal in the Alps has still not been thoroughly investigated.Aiming to fill this gap with a focus on high-elevation environments,minimum and maximum daily air temperature acquired by 23 automatic weather station were used.The results show that the mean annual values of minimum and maximum temperature for the 1991-2020 climate normal in the Alps are-2.4℃ and 4.4℃,respectively,with a warming rate of 0.5℃/10 years.The mean annual temperature comparison between 1961-1990 and 1971-2000,1961-1990 and 1981-2010,1961-1990 and 1991-2020 climate normal show an increase of 0.3℃,0.5℃ and 0.9℃,respectively.The results also confirm that seasonal and annual temperatures are rising through the whole Alpine arc,mainly in summer and autumn.This work highlights that annual minimum and maximum temperature do not seem to be affected by a positive elevation-dependent warming.Instead,a positive elevation-dependent warming in the maximum values of the annual minimum temperature was found.If anthropogenic emissions maintain the trend of the last decades,the expected mean annual temperature of the 2001-2030 climate normal is-0.2℃,with an increase of 0.5℃ if compared to the 1991-2020 climate normal and with an increase of 1.5℃ if compared to the 1961-1990 climate normal.This study highlights the warming rate that is now present in the European Alps,provides indications on the warming rate that will occur in the coming years and highlights the importance of carrying out investigations that consider not only the last 30-year climate normal,but also the most recent 30-year climate normal by comparing them with each other.
文摘Groundwater is reported to account for 87% of all drinking water resources in Dhaka which has suffered a decline of up to 75 m in some specific location. Over-extraction of groundwater is an extensive social problem in Dhaka and Gazipur city which needs to be investigating thoroughly. This study presents the diagnosis of groundwater depletion pattern and the yearly rate of decline over the last three decades for Dhaka and Gazipur metropolitan area. Groundwater data were collected from the relevant institutions in order to analyse the trend line and the rate of decline of groundwater levels for more than 30 years period to understand the long-time variability. Ten individual stations datasets for GWL have been analyzed for Dhaka and Gazipur within a selected reference time period (1980-2012). The highest depleted GWL were found in the Mirpur station which is now 68 m below ground. To find out the time span when the depletion rate is highest, the rate of decline of all datasets has been computed which shows that 1998-2005 is the consecutive eight years time span with the fastest depletion rate. On the other hand, the annual trend-line analysis shows rapid depletion pattern after the year 2000.
文摘Trends in 20 extreme indices of temperature and precipitation are examined for Sri Lanka using high-quality datasets for 19 meteorological stations, for a period between 1980 and 2015. It is evident that annually averaged mean minimum temperatures are increasing across most of Sri Lanka. The difference between maximum and minimum temperatures, diurnal temperature range is decreasing, indicating that the minimum temperature is increasing faster than the maximum temperature. Significant decrease in the annual occurrence of cold nights and increase in the annual occurrence of warm nights are also obvious. When compared with temperature changes, less spatially coherent pattern of change and a lower level of statistical significance were observed in precipitation indices. The annual total precipitation (PRCPTOT) has indicated a significant increasing over 1980-2015. More than 80% of stations showed an increasing trend in precipitation indices. The trends in extreme precipitation events such as maximum one-day precipitation, maximum five-day precipitation, and total precipitation on extreme rainfall days (R95p and R99p) are increasing at most locations, indicating that the intensity of the rainfall is increasing. Increase of precipitation extreme trends indicates that occurrence of extreme rainfall events notably influences total annual precipitation in Sri Lanka. Therefore, the observed increases in total rainfall observed in many locations may be due in part to an increase in of extreme rainfall events. Patterns of change in precipitation extremes are more heavily influencing the climate variability by aggravating the variability, significantly influencing climate sensitive sectors such as agriculture and water resource management.
文摘Despite the extreme events impact on various climate events frequency and intensity in many developing countries, there has been dearth information on daily climate trends and climatic extremes. This study comes to characterize the climate type and its evolution in Morocco, specially the two regions Beni Mellal-Khenifra and Daraa-Tafilalt. RClimdex software has been used to calculate pluvio-thermal and ombro-thermic indices in the studied stations to reveal climate type in the two regions, their evolutions, and the daily extreme temperatures and precipitations. A cartographic representation has been done for the calculated indices and climatic trends in the stations from 1970 to 2016. As results, the temperature trend for hot day’s number shows a significant increase, while the cold night’s numbers, warm sequences, and precipitation are gradually decreases especially at Khouribga and Midelt. These observed modifications influence negatively the annual rainfall total in the year, the consecutive wet days, the maximums rainy days, and the increase of consecutively dry days. As a conclusion, the Martonne aridity and ombro-thermic indices, show that the temperatures and precipitations evolutions do not induce a change in the climate type for the studied regions.
