A compilation of paleoclimate records from ice core, tree-rings, lake sediments and historical documents provides a view of temperature change in China over the recent 2000 years. For all-China temperature reconstruct...A compilation of paleoclimate records from ice core, tree-rings, lake sediments and historical documents provides a view of temperature change in China over the recent 2000 years. For all-China temperature reconstruction, six sub-stages are identified for the last two millennia. Around AD 0－240, AD 800－1100, AD 1320－1400 and the period from AD 1880 on were warm while around AD 240－800, AD 1100－1320, AD 1400－1880 were cold. Also, temperature varied from region to region in each of the warm or cold periods. The Eastern Han warm period (0－AD 240), the cold period covering the span of Wei, Jin, and the Southern and Northern Dynasties, the MWP (AD 800－1100) and succeeding LIA occurred in eastern China and the Qilian Mountains. Only the first two climatic events were recorded in Guliya ice core while the so-called MWP and LIA was far weaker. Also, the warming between AD 800 and 1100 didn′t occur in the south of Xizang (Tibet) Plateau. Instead, the southern Xizang Plateau experienced warming in AD 1150－1400. The aggregated China temperature agrees well with North-hemisphere temperature in the past millennia, indicating close relationship of temperature changes between China and North-hemisphere.展开更多
Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world’s three prairies, is undergoing a process of prominent warming and dr...Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world’s three prairies, is undergoing a process of prominent warming and drying. It is essential to investigate the effects of climatic change （temperature and precipitation） on vegetation dynamics for a better understanding of climatic change. NDVI （Normalized Difference Vegetation Index）, reflecting characteristics of plant growth, vegetation coverage and biomass, is used as an indicator to monitor vegetation changes. GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation changes in Hulun Buir Grassland. The responses of vegetation coverage to climatic change on the yearly, seasonal and monthly scales were analyzed combined with temperature and precipitation data of seven meteorological sites. In the past 30 years, vegetation coverage was more correlated with climatic factors, and the correlations were dependent on the time scales. On an inter-annual scale, vegetation change was better correlated with precipitation, suggesting that rainfall was the main factor for driving vegetation changes. On a seasonal-interannual scale, correlations between vegetation coverage change and climatic factors showed that the sensitivity of vegetation growth to the aqueous and thermal condition changes was different in different seasons. The sensitivity of vegetation growth to temperature in summers was higher than in the other seasons, while its sensitivity to rainfall in both summers and autumns was higher, especially in summers. On a monthly-interannual scale, correlations between vegetation coverage change and climatic factors during growth seasons showed that the response of vegetation changes to temperature in both April and May was stronger. This indicates that the temperature effect occurs in the early stage of vegetation growth. Correlations between vegetation growth and precipitation of the month before the current month, were better from May to August, showing a hysteresis response of vegetation growth to rainfall. Grasses get green and begin to grow in April, and the impacts of temperature on grass growth are obvious. The increase of NDVI in April may be due to climatic warming that leads to an advanced growth season. In summary, relationships between monthly-interannual variations of vegetation coverage and climatic factors represent the temporal rhythm controls of temperature and precipitation on grass growth largely.展开更多
Examining the direct and indirect effects of climatic factors on vegetation growth is critical to understand the complex linkage between climate change and vegetation dynamics. Based on the Moderate Resolution Imaging...Examining the direct and indirect effects of climatic factors on vegetation growth is critical to understand the complex linkage between climate change and vegetation dynamics. Based on the Moderate Resolution Imaging Spectroradiometer(MODIS) Normalized Difference Vegetation Index(NDVI) data and meteorological data(temperature and precipitation) from 2001 to 2012, the trend of vegetation dynamics were examined in the Ziya-Daqing basins, China. The path analysis was used to obtain the information on the relationships among climatic factors and their effects on vegetation growth. It was found that the trends of growing season NDVI were insignificant in most plain dry land, while the upward trends were significant in forest, grass and dry land in Taihang Mountains. According to the path analysis, in 23% of the basins the inter-annual NDVI variation was dominated by the direct effect of precipitation, in 5% by the direct effects of precipitation and temperature, and in less than 1% by the direct effect of temperature or indirect effects of these two climatic factors. It indicated that precipitation significantly affected the vegetation growth in the whole basins, and this effect was not regulated by temperature. Precipitation increase(especially in July, August and September) was favorable to greenness enhancement. Summer temperature rising showed negative effect on plant productivity enhancement, but temperature rise in April was beneficial for the vegetation growth. When April temperature increases by 1℃, the onset date of greenness for natural vegetation will be 2 days in advance. There was a lag-time effect of precipitation or temperature on monthly NDVI for all land use types except grass.展开更多
Climate change is supposed to have influences on water quality and ecosystem. However, only few studies have assessed the effect of climate change on environmental toxic contaminants in urban lakes. In this research, ...Climate change is supposed to have influences on water quality and ecosystem. However, only few studies have assessed the effect of climate change on environmental toxic contaminants in urban lakes. In this research, response of several toxic contaminants in twelve urban lakes in Beijing, China, to the seasonal variations in climatic factors was studied. Fluorides, volatile phenols, arsenic, selenium, and other water quality parameters were analyzed monthly from2009 to 2012. Multivariate statistical methods including principle component analysis, cluster analysis, and multiple regression analysis were performed to study the relationship between contaminants and climatic factors including temperature, precipitation, wind speed, and sunshine duration. Fluoride and arsenic concentrations in most urban lakes exhibited a significant positive correlation with temperature/precipitation, which is mainly caused by rainfall induced diffuse pollution. A negative correlation was observed between volatile phenols and temperature/precipitation, and this could be explained by their enhanced volatilization and biodegradation rates caused by higher temperature. Selenium did not show a significant response to climatic factor variations, which was attributed to low selenium contents in the lakes and soils. Moreover, the response degrees of contaminants to climatic variations differ among lakes with different contamination levels. On average, temperature/precipitation contributed to 8%, 15%, and 12% of the variations in volatile phenols, arsenic, and fluorides,respectively. Beijing is undergoing increased temperature and heavy rainfall frequency during the past five decades. This study suggests that water quality related to fluoride and arsenic concentrations of most urban lakes in Beijing is becoming worse under this climate change trend.展开更多
The recorded meteorological data of monthly mean surface air temperature from 72 meteorological stations over the Qinghal-Tibet Plateau in the period of 1960-2003 have been analyzed by using Empirical Orthogonal Funct...The recorded meteorological data of monthly mean surface air temperature from 72 meteorological stations over the Qinghal-Tibet Plateau in the period of 1960-2003 have been analyzed by using Empirical Orthogonal Function （EOF） method, to understand the detailed features of its temporal and spatial variations. The results show that there was a high consistency of the monthly mean surface air temperature, with a secondarily different variation between the north and the south of the plateau. Warming trend has existed at all stations since the 1960s, while the warming rates were different in various zones. The source regions of big rivers had intense warming tendency. June, November and December were the top three fast-warming months since the 1960s; while April, July and September presented dramatic warming tendency during the last decade.展开更多
High topographies, such as the Tibetan plateau （TP） in China, have been considered as the sensitive areas in response to global climate change. By analyzing the relationship between warming structure and altitude （...High topographies, such as the Tibetan plateau （TP） in China, have been considered as the sensitive areas in response to global climate change. By analyzing the relationship between warming structure and altitude （1 000-5 000 m） in the TP and its vicinities using the 46-year January mean observed temperature data, we found that there was a significant altitude effect of temperature warming onset time （mutation time） on the plateau and the neighboring regions： the higher the altitude, the later the climate warming happens, and vice versa. There also seems a slight altitude effect on warming magnitude： the higher the altitude, the less the warming magnitude. Therefore, the temperature warming in the high altitude area of the TP （below 5 000 m） responds to global warming less sensitively than the low-altitude neighboring areas both in onset time and magnitude, which may be mainly caused by high albedo and large thermal capacity of the ice/snow cover on the higher part of the plateau and possible heat island effect in the lower part of the plateau.展开更多
Based on the analyses of environmental proxy data in lake sediments and instrumental records of Xinjiang in northwest China, the Holocene climate and hydrological variability and its environmental responses were studi...Based on the analyses of environmental proxy data in lake sediments and instrumental records of Xinjiang in northwest China, the Holocene climate and hydrological variability and its environmental responses were studied in different time scales and regions. The results showed that the Holocene climate variability had obvious differences between the north and south of Xinjiang. In northern Xinjiang, the Holocene climate was dry in the early period, humid in the middle period, and then changed to dry in the late period. However, the climate transition times were not consistent in different regions. In southern Xin- jiang, although there were many different types of climate change patterns inferred from different catch- ments, the warm and wet climate was recorded in most lake sediments in the middle Holocene. According to comparisons of some millennium scale records in lake sediments, the climate was warm and dry in the past 100 years. It can be concluded the climate showed a trend of aridity in Holocene. Especially in recent 50 years, the lake area has been shrinking rapidly because of the population growth and social economic development, which brings some environmental problems. Lake level and area changes were sensitively affected by the climate variation in geological history of Xinjiang and the lake level will continue to shrink because of the drought climate and strengthened human activities.展开更多
The preliminary analysis of climatic variation in China during the last 39 years has been made in this paper. The results show that although the global climate is getting warmer, some parts of China are cooling. The w...The preliminary analysis of climatic variation in China during the last 39 years has been made in this paper. The results show that although the global climate is getting warmer, some parts of China are cooling. The warming only occurs in Northeast, North and the west part of Northwest China while the areas between about 35°N and Nanling Mountain, east of the Tibetan Plateau in China are getting cooler. The cooling centers are located in Sichuan, the south part of Shaanxi and the north part of Yunnan respectively. According to the theory of greenhouse effect, there are much precipitation at low and high latitudes and less precipitation in middle latitude. However, the precipitation in the most parts of China has been decreased, especially in North and Northwest China.展开更多
Total sea level variations（SLVs） are caused by two major components：steric variations due to thermal expansion of seawater,and mass-induced variations due to mass exchange between ocean and land.In this study,the g...Total sea level variations（SLVs） are caused by two major components：steric variations due to thermal expansion of seawater,and mass-induced variations due to mass exchange between ocean and land.In this study,the global SLV and its steric and mass components were estimated by satellite altimetry,Argo float data and the Gravity Recovery and Climate Experiment（GRACE） data over 2005-2014.Space gravimetry observations from GRACE suggested that two-thirds of the global mean sea level rise rate observed by altimetry（i.e.,3.1 ± 0.3 mm/a from 2005 to 2014） could be explained by an increase in ocean mass.Furthermore,the global mean sea level was observed to drop significantly during the2010/2011 La Nina event,which may be attributed to the decline of ocean mass and steric SLV.Since early 2011,the global mean sea level began to rise rapidly,which was attributed to an increase in ocean mass.The findings in this study suggested that the global mean sea-level budget was closed from 2005 to 2014 based on altimetry,GRACE,and Argo data.展开更多
[Objective] The research aimed to study the influence of climatic variation on rice production in Anqing zone.[Method] Based on temperature and precipitation data in rice growth period (May-November) during 1980-2009,...[Objective] The research aimed to study the influence of climatic variation on rice production in Anqing zone.[Method] Based on temperature and precipitation data in rice growth period (May-November) during 1980-2009,by using five-year sliding average method,the moving average charts of temperature and rainfall were made.The variation characteristics of main factors (temperature and precipitation) which affected rice growth were analyzed.By using line moving average simulation method,the climatic yield was separated,and the influence of climatic factor on rice yield in Anqing zone was analyzed.[Result] In recent 30 years,the temperature presented rise trend in rice growth period in Anqing zone.Started from 1993,the rise was obvious.But the rainfall had decline trend,and the rainfall was stable after 2000.These were the climatic background for that rice yield had a wave of quick increase after 2000.Seen from the separated results of trend yield and meteorological yield,the variation range of relative meteorological yield was big,and the maximum yield reduction reached 27.5%.In recent 30 years,there were four yield reduction years.The relationship between meteorological yield of rice and temperature was positive correlation except in September.The excessive rainfall in the rice harvest period had unfavorable influence on rice yield.The drought was the main meteorological agricultural disaster which affected rice yield in the zone.[Conclusion] The research provided the theoretical basis for improving grain yield in Anqing zone.展开更多
Permafrost temperatures from the surface down to about 9 m from 3 boreholes distributed around Kangiqsualujjuaq village on the coast of Hudson Strait were recorded and analyzed for the period 1989 1998. The results i...Permafrost temperatures from the surface down to about 9 m from 3 boreholes distributed around Kangiqsualujjuaq village on the coast of Hudson Strait were recorded and analyzed for the period 1989 1998. The results indicate that the permafrost is getting warm along the southern shore of Hudson Strait from 1993 to 1998 though it became cooling for the past 40 a or more. The observed trend in the order of 0.098℃/a at the 9 m depth is consistent with the long term regional warming observed in air temperatures. It also coincides with that all the global circulation models predict an enhanced warming in polar regions associated with the increase in concentration of greenhouse gases in the atmosphere.展开更多
By using the daily average relative humidity data in Urumqi during 1961-2000,the basic climate characteristics and the variation trend of relative humidity in Urumqi in recent 40 years were analyzed.The results showed...By using the daily average relative humidity data in Urumqi during 1961-2000,the basic climate characteristics and the variation trend of relative humidity in Urumqi in recent 40 years were analyzed.The results showed that the yearly average relative humidity in Urumqi was 57.5%.The relative humidity in winter was 77.5% which was the biggest all the year round,and the relative humidity in summer was 41.2% which was the smallest.The relative humidity in spring,summer,autumn,winter and the yearly relative humidity all displayed the increase trend.The yearly mean relative humidity had the periods of mainly 2,3-4 and quasi-7 years.The periodic oscillation of quasi-7 years was the strongest.展开更多
In the context of climate change, the study of the variability of the climatic extremes in several regions of the world is of capital importance. This study has as main objective to analyze the variability of extreme ...In the context of climate change, the study of the variability of the climatic extremes in several regions of the world is of capital importance. This study has as main objective to analyze the variability of extreme temperature events in the Beninese basin of the Niger River for the recent and the near future. To achieve this objective, seven (07) extreme temperature indices based on historical daily temperature observations (1976 to 2019) and REMO RCM simulation outputs of RCP4.5 and RCP8.5 scenarios (2021-2050) were calculated. The obtained results were represented by calculating the means for each index and analyzing the trends and their significance by the Mann-Kendall method. The results show that the indices of extreme temperature intensity (TNn, TXx, and DTR), and those related to the frequency of warm sequences (WSDI, TN90p and TX90p) have experienced a significant increase in the past. This increase will continue until 2050. In contrast, the cold sequence frequency index (CSDI) decrease over the historical period as well as over the future period. These indices show much more change with the RCP8.5 scenario than with the RCP4.5 of the REMO climate model. Only the TXx and CSDI indices show statistically significant changes at all stations.展开更多
Decadal/interdecadal climate variability is an important element in the CLIVAR (Climate Variability and Predictability) and has received much attention in the world. Many studies in relation to interdecadal variation ...Decadal/interdecadal climate variability is an important element in the CLIVAR (Climate Variability and Predictability) and has received much attention in the world. Many studies in relation to interdecadal variation have also been completed by Chinese scientists in recent years. In this paper, an introduction in outline for interdecadal climate variation research in China is presented. The content includes the features of interdecadal climate variability in China, global warming and interdecadal temperature variability, the NAO (the North Atlantic Oscillation)/NPO (the North Pacific Oscillation) and interdecadal climate variation in China, the interdecadal variation of the East Asian monsoon, the interdecadal mode of SSTA (Sea Surface Temperature Anomaly) in the North Pacific and its climate impact, and abrupt change feature of the climate.展开更多
This study examines the expansion of drylands and regional climate change in northern China by analyzing the variations in aridity index （AI）, surface air temperature （SAT）, precipitation and potential evapotransp...This study examines the expansion of drylands and regional climate change in northern China by analyzing the variations in aridity index （AI）, surface air temperature （SAT）, precipitation and potential evapotranspiration （PET） from 1948 to 2008. It is found that the drylands of northern China have expanded remarkably in the last 61 years. The area of drylands of the last 15 years （1994--2008） is 0.65 × 106 km2 （12%） larger than that in the period 1948-62. The boundary of drylands has extended eastward over Northeast China by about 2 °of longitude and by about 1° of latitude to the south along the middle- to-lower reaches of the Yellow River. A zonal band of expansion of semi-arid regions has occurred, stretching from western Heilongjiang Province to southern Gansu Province, while shifts to the east of semi-arid regions in dry subhumid regions have also occurred. Results show that the aridity trend of drylands in northern China is highly correlated with the long-term trend of precipitation and PET, and the expansion of semi-arid regions plays a dominant role in the areal extent of drylands, which is nearly 10 times larger than that in arid and subhumid regions.展开更多
This article discusses the interannual variation of the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO), its relationship with the interdecadal climate variation in China which is associated with ...This article discusses the interannual variation of the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO), its relationship with the interdecadal climate variation in China which is associated with the climate jump in the Northern Hemisphere in the 1960’s, using the data analyses. It is clearly shown that both the amplitudes of the NAO and NPO increase obviously in the 1960’s and the main period of the oscillations changes from 3-4 years before the 1960’s to 8–15 years after the 1960’s. Therefore, interdecadal climate variation in China or the climate jump in the 1960’s is closely related to the anomalies of the NAO and NPO. Key words North Atlantic Oscillation (NAO) - North Pacific Oscillation (NPO) - Climate Jump - Interdecadal climate variation This work was supported by National Key Basic Science Program in China (G1998040903), Chinese Academy of Science and the National Natural Science Fundation of China (Grant No.49823002).The authors are also grateful to Ms. Wang Xuan for typing the manuscript.展开更多
Based on the 1990, 2000 and 2011 Landsat TM/ETM+ remote sensing data, glacier information of three periods in the Chinese Tianshan Mountains were extracted by using ratio threshold method(TM3/TM5) and visual interpret...Based on the 1990, 2000 and 2011 Landsat TM/ETM+ remote sensing data, glacier information of three periods in the Chinese Tianshan Mountains were extracted by using ratio threshold method(TM3/TM5) and visual interpretation, combined with digital processing of satellite images and analysis in GIS. The climate data in the surrounding area were analyzed by using linear regression, Mann-Kendall abrupt test, and Morlet wavelet analysis. Study results showed that: over the 23 years investigation, the glacier areas have markedly decreased. In the last 12 years(2000 to 2011), the rate of retreat has begun to accelerate. The most dramatic glacier shrinkage occurred in the central region, the lowest in the eastern region. The mean summer temperature and warm precipitation in Chinese Tianshan Mountains had an increasing trend, with rates of 0.22°C /10 a and 5.1mm/10 a from 1960 to 2011, respectively. Mean summer temperature have experienced a strong increase in 1998. The analysis of the results showed that the rise of mean summer temperature was the main factor that contributed to glacier shrinkage. Regional differences of glacier area changes were investigated by analyzing glacier behavior in five study sub-regions; regional differences are related to local climate, to the relative proportion of glaciers in different size classes, altitudinal and aspect distribution of glaciated areas. In addition, the lag theory indicated that glaciers may accelerate the retreat in the next decade, considering climate trends recognized for the period 2000-2011.展开更多
Vegetation plays a key role in maintaining ecosystem stability,promoting biodiversity conservation,serving as windbreaks,and facilitating sand fixation in deserts.Based on the Moderate Resolution Imaging Spectroradiom...Vegetation plays a key role in maintaining ecosystem stability,promoting biodiversity conservation,serving as windbreaks,and facilitating sand fixation in deserts.Based on the Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index(MODIS NDVI)and climate data,a Theil-Sen median trend analysis combined with the Mann-Kendall test and partial correlation and residual analyses were employed to explore spatiotemporal patterns of vegetation dynamics and key drivers in the Badain Jaran and Tengger deserts and Mu Us Sandy Land.Data were collected during the growing season between 2001 and 2020.Further analyses quantified the relative contribution of climate variation and anthropogenic activities to NDVI changes.Results revealed a predominantly increasing trend for average NDVI.The spread of average annual NDVI and growth trends of the vegetation were determined to be influenced by spatial differences.The area with improved vegetation was greater than that of the degraded region.Climate variability and human activities were driving forces controlling vegetation cover changes,and their effects on vegetation dynamics varied by region.The response of vegetation dynamics was stronger for precipitation than temperature,indicating that precipitation was the main climate variable influencing the NDVI changes.The relative role of human activities was responsible for>70%of the changes,demonstrating that human activities were the main driving factor of the NDVI changes.The implementation of ecological engineering is a key driver of increased vegetation coverage and has improved regional environmental quality.These results enhance our knowledge regarding NDVI change affected by climate variation and human activities and can provide future theoretical guidance for ecological restoration in arid areas.展开更多
The spatial distribution and monthly/annual variation of foggy days in China are analyzed based on the monthly mean fog data collected from 604 observational stations for the period 1961-2000. Results show that there ...The spatial distribution and monthly/annual variation of foggy days in China are analyzed based on the monthly mean fog data collected from 604 observational stations for the period 1961-2000. Results show that there are six fog regions in China： the middle reaches of the Yangtze River, coastal areas, Yunnan-Gulzhou Plateau, eastern Gansu-Shaanxi region, Huaihe River valley, Tianshan mountainous area and northern Xinjiang. On the whole the interannual variation trend of foggy days is descending, especially an obvious decline after the 1980s. The areas where the foggy days have obvious tendency present a southwest-northeast direction. The rising trend regions alternate with descending trend regions, forming a SE-NW directional wave structure. In general, the number of foggy days in autumn and winter is larger than in spring and summer over most fog regions. The monthly variation curves of foggy days are bimodal in the coastal area of the Yellow Sea and northern Xinjiang, and unimodal in other regions.展开更多
A case study on the driving forces of desertification in the semi-arid region was carried out in the Ejin Horo Banner of Inner Mongolia. The occurrence and development of desertification were demonstrated and its driv...A case study on the driving forces of desertification in the semi-arid region was carried out in the Ejin Horo Banner of Inner Mongolia. The occurrence and development of desertification were demonstrated and its driving factors were identified and analyzed. The results obtained indicated that over-reclamation of land overgrazing and denudation of natural vegetation cover were immediate and dominant factors causing land vulnerability to desertification. For a better understanding of the deep-rooted causes of the inappropriate land use and agricultural practices, the problems arising from various socioeconomic facets were comprehensively discussed.展开更多
基金Under the auspices of the KZCX2-304 and KI 951-A1-202-04 Project of the Chinese Academy of Sciences.
文摘A compilation of paleoclimate records from ice core, tree-rings, lake sediments and historical documents provides a view of temperature change in China over the recent 2000 years. For all-China temperature reconstruction, six sub-stages are identified for the last two millennia. Around AD 0－240, AD 800－1100, AD 1320－1400 and the period from AD 1880 on were warm while around AD 240－800, AD 1100－1320, AD 1400－1880 were cold. Also, temperature varied from region to region in each of the warm or cold periods. The Eastern Han warm period (0－AD 240), the cold period covering the span of Wei, Jin, and the Southern and Northern Dynasties, the MWP (AD 800－1100) and succeeding LIA occurred in eastern China and the Qilian Mountains. Only the first two climatic events were recorded in Guliya ice core while the so-called MWP and LIA was far weaker. Also, the warming between AD 800 and 1100 didn′t occur in the south of Xizang (Tibet) Plateau. Instead, the southern Xizang Plateau experienced warming in AD 1150－1400. The aggregated China temperature agrees well with North-hemisphere temperature in the past millennia, indicating close relationship of temperature changes between China and North-hemisphere.
基金Open Project of Hulun Buir Grassland Ecosystem Observation and Research Station, No.2010-10Open Project of Ministry of Agriculture Key Laboratory of Resource Remote Sensing and Digital Agriculture, No.RDA0803+1 种基金 No.RDA0903Basic Research Project of the Ministry of Science and Technology, No.2007FY110300
文摘Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world’s three prairies, is undergoing a process of prominent warming and drying. It is essential to investigate the effects of climatic change （temperature and precipitation） on vegetation dynamics for a better understanding of climatic change. NDVI （Normalized Difference Vegetation Index）, reflecting characteristics of plant growth, vegetation coverage and biomass, is used as an indicator to monitor vegetation changes. GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation changes in Hulun Buir Grassland. The responses of vegetation coverage to climatic change on the yearly, seasonal and monthly scales were analyzed combined with temperature and precipitation data of seven meteorological sites. In the past 30 years, vegetation coverage was more correlated with climatic factors, and the correlations were dependent on the time scales. On an inter-annual scale, vegetation change was better correlated with precipitation, suggesting that rainfall was the main factor for driving vegetation changes. On a seasonal-interannual scale, correlations between vegetation coverage change and climatic factors showed that the sensitivity of vegetation growth to the aqueous and thermal condition changes was different in different seasons. The sensitivity of vegetation growth to temperature in summers was higher than in the other seasons, while its sensitivity to rainfall in both summers and autumns was higher, especially in summers. On a monthly-interannual scale, correlations between vegetation coverage change and climatic factors during growth seasons showed that the response of vegetation changes to temperature in both April and May was stronger. This indicates that the temperature effect occurs in the early stage of vegetation growth. Correlations between vegetation growth and precipitation of the month before the current month, were better from May to August, showing a hysteresis response of vegetation growth to rainfall. Grasses get green and begin to grow in April, and the impacts of temperature on grass growth are obvious. The increase of NDVI in April may be due to climatic warming that leads to an advanced growth season. In summary, relationships between monthly-interannual variations of vegetation coverage and climatic factors represent the temporal rhythm controls of temperature and precipitation on grass growth largely.
基金Under the auspices of National Natural Science Foundation of China(No.41471026,31171451)Strategic Science and Technology Program in the Thirteenth Five-Year Plan of Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Sciences(No.2012ZD003)
文摘Examining the direct and indirect effects of climatic factors on vegetation growth is critical to understand the complex linkage between climate change and vegetation dynamics. Based on the Moderate Resolution Imaging Spectroradiometer(MODIS) Normalized Difference Vegetation Index(NDVI) data and meteorological data(temperature and precipitation) from 2001 to 2012, the trend of vegetation dynamics were examined in the Ziya-Daqing basins, China. The path analysis was used to obtain the information on the relationships among climatic factors and their effects on vegetation growth. It was found that the trends of growing season NDVI were insignificant in most plain dry land, while the upward trends were significant in forest, grass and dry land in Taihang Mountains. According to the path analysis, in 23% of the basins the inter-annual NDVI variation was dominated by the direct effect of precipitation, in 5% by the direct effects of precipitation and temperature, and in less than 1% by the direct effect of temperature or indirect effects of these two climatic factors. It indicated that precipitation significantly affected the vegetation growth in the whole basins, and this effect was not regulated by temperature. Precipitation increase(especially in July, August and September) was favorable to greenness enhancement. Summer temperature rising showed negative effect on plant productivity enhancement, but temperature rise in April was beneficial for the vegetation growth. When April temperature increases by 1℃, the onset date of greenness for natural vegetation will be 2 days in advance. There was a lag-time effect of precipitation or temperature on monthly NDVI for all land use types except grass.
基金supported by the Major State Basic Research Development Program(No.2010CB951104)the National Science Foundation for Distinguished Young Scholars(No.51325902)the National Natural Science Foundation of China(No.51279010)
文摘Climate change is supposed to have influences on water quality and ecosystem. However, only few studies have assessed the effect of climate change on environmental toxic contaminants in urban lakes. In this research, response of several toxic contaminants in twelve urban lakes in Beijing, China, to the seasonal variations in climatic factors was studied. Fluorides, volatile phenols, arsenic, selenium, and other water quality parameters were analyzed monthly from2009 to 2012. Multivariate statistical methods including principle component analysis, cluster analysis, and multiple regression analysis were performed to study the relationship between contaminants and climatic factors including temperature, precipitation, wind speed, and sunshine duration. Fluoride and arsenic concentrations in most urban lakes exhibited a significant positive correlation with temperature/precipitation, which is mainly caused by rainfall induced diffuse pollution. A negative correlation was observed between volatile phenols and temperature/precipitation, and this could be explained by their enhanced volatilization and biodegradation rates caused by higher temperature. Selenium did not show a significant response to climatic factor variations, which was attributed to low selenium contents in the lakes and soils. Moreover, the response degrees of contaminants to climatic variations differ among lakes with different contamination levels. On average, temperature/precipitation contributed to 8%, 15%, and 12% of the variations in volatile phenols, arsenic, and fluorides,respectively. Beijing is undergoing increased temperature and heavy rainfall frequency during the past five decades. This study suggests that water quality related to fluoride and arsenic concentrations of most urban lakes in Beijing is becoming worse under this climate change trend.
基金Under the auspices of the National Natural Science Foundation of China (No. 40401054, No. 40121101), Hundred Talents Program of Chinese Academy of Sciences, President Foundation of Chinese Academy of Sciences, Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX3-SW-339), National Basic Research Program of China (No. 2005CB422004)
文摘The recorded meteorological data of monthly mean surface air temperature from 72 meteorological stations over the Qinghal-Tibet Plateau in the period of 1960-2003 have been analyzed by using Empirical Orthogonal Function （EOF） method, to understand the detailed features of its temporal and spatial variations. The results show that there was a high consistency of the monthly mean surface air temperature, with a secondarily different variation between the north and the south of the plateau. Warming trend has existed at all stations since the 1960s, while the warming rates were different in various zones. The source regions of big rivers had intense warming tendency. June, November and December were the top three fast-warming months since the 1960s; while April, July and September presented dramatic warming tendency during the last decade.
基金supported by the National Natural Science Foundation of China (Nos.40830743,40771187)Scientific Effort of Education Department of Shaanxi Province (No.09JK429)
文摘High topographies, such as the Tibetan plateau （TP） in China, have been considered as the sensitive areas in response to global climate change. By analyzing the relationship between warming structure and altitude （1 000-5 000 m） in the TP and its vicinities using the 46-year January mean observed temperature data, we found that there was a significant altitude effect of temperature warming onset time （mutation time） on the plateau and the neighboring regions： the higher the altitude, the later the climate warming happens, and vice versa. There also seems a slight altitude effect on warming magnitude： the higher the altitude, the less the warming magnitude. Therefore, the temperature warming in the high altitude area of the TP （below 5 000 m） responds to global warming less sensitively than the low-altitude neighboring areas both in onset time and magnitude, which may be mainly caused by high albedo and large thermal capacity of the ice/snow cover on the higher part of the plateau and possible heat island effect in the lower part of the plateau.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-EW-308)the National Basic Research Program of China (2006FY110600)the National Natural Science Foundation of China (41071139 and 40971117)
文摘Based on the analyses of environmental proxy data in lake sediments and instrumental records of Xinjiang in northwest China, the Holocene climate and hydrological variability and its environmental responses were studied in different time scales and regions. The results showed that the Holocene climate variability had obvious differences between the north and south of Xinjiang. In northern Xinjiang, the Holocene climate was dry in the early period, humid in the middle period, and then changed to dry in the late period. However, the climate transition times were not consistent in different regions. In southern Xin- jiang, although there were many different types of climate change patterns inferred from different catch- ments, the warm and wet climate was recorded in most lake sediments in the middle Holocene. According to comparisons of some millennium scale records in lake sediments, the climate was warm and dry in the past 100 years. It can be concluded the climate showed a trend of aridity in Holocene. Especially in recent 50 years, the lake area has been shrinking rapidly because of the population growth and social economic development, which brings some environmental problems. Lake level and area changes were sensitively affected by the climate variation in geological history of Xinjiang and the lake level will continue to shrink because of the drought climate and strengthened human activities.
基金This work is supported by National Environment and Protect Agency under Program 891205
文摘The preliminary analysis of climatic variation in China during the last 39 years has been made in this paper. The results show that although the global climate is getting warmer, some parts of China are cooling. The warming only occurs in Northeast, North and the west part of Northwest China while the areas between about 35°N and Nanling Mountain, east of the Tibetan Plateau in China are getting cooler. The cooling centers are located in Sichuan, the south part of Shaanxi and the north part of Yunnan respectively. According to the theory of greenhouse effect, there are much precipitation at low and high latitudes and less precipitation in middle latitude. However, the precipitation in the most parts of China has been decreased, especially in North and Northwest China.
基金supported by the National Key Basic Research Program of China(973 program,2012CB957703 and2013CB733305)the National Natural Science Foundation of China(41431070,41174066 and 41321063)
文摘Total sea level variations（SLVs） are caused by two major components：steric variations due to thermal expansion of seawater,and mass-induced variations due to mass exchange between ocean and land.In this study,the global SLV and its steric and mass components were estimated by satellite altimetry,Argo float data and the Gravity Recovery and Climate Experiment（GRACE） data over 2005-2014.Space gravimetry observations from GRACE suggested that two-thirds of the global mean sea level rise rate observed by altimetry（i.e.,3.1 ± 0.3 mm/a from 2005 to 2014） could be explained by an increase in ocean mass.Furthermore,the global mean sea level was observed to drop significantly during the2010/2011 La Nina event,which may be attributed to the decline of ocean mass and steric SLV.Since early 2011,the global mean sea level began to rise rapidly,which was attributed to an increase in ocean mass.The findings in this study suggested that the global mean sea-level budget was closed from 2005 to 2014 based on altimetry,GRACE,and Argo data.
文摘[Objective] The research aimed to study the influence of climatic variation on rice production in Anqing zone.[Method] Based on temperature and precipitation data in rice growth period (May-November) during 1980-2009,by using five-year sliding average method,the moving average charts of temperature and rainfall were made.The variation characteristics of main factors (temperature and precipitation) which affected rice growth were analyzed.By using line moving average simulation method,the climatic yield was separated,and the influence of climatic factor on rice yield in Anqing zone was analyzed.[Result] In recent 30 years,the temperature presented rise trend in rice growth period in Anqing zone.Started from 1993,the rise was obvious.But the rainfall had decline trend,and the rainfall was stable after 2000.These were the climatic background for that rice yield had a wave of quick increase after 2000.Seen from the separated results of trend yield and meteorological yield,the variation range of relative meteorological yield was big,and the maximum yield reduction reached 27.5%.In recent 30 years,there were four yield reduction years.The relationship between meteorological yield of rice and temperature was positive correlation except in September.The excessive rainfall in the rice harvest period had unfavorable influence on rice yield.The drought was the main meteorological agricultural disaster which affected rice yield in the zone.[Conclusion] The research provided the theoretical basis for improving grain yield in Anqing zone.
文摘Permafrost temperatures from the surface down to about 9 m from 3 boreholes distributed around Kangiqsualujjuaq village on the coast of Hudson Strait were recorded and analyzed for the period 1989 1998. The results indicate that the permafrost is getting warm along the southern shore of Hudson Strait from 1993 to 1998 though it became cooling for the past 40 a or more. The observed trend in the order of 0.098℃/a at the 9 m depth is consistent with the long term regional warming observed in air temperatures. It also coincides with that all the global circulation models predict an enhanced warming in polar regions associated with the increase in concentration of greenhouse gases in the atmosphere.
文摘By using the daily average relative humidity data in Urumqi during 1961-2000,the basic climate characteristics and the variation trend of relative humidity in Urumqi in recent 40 years were analyzed.The results showed that the yearly average relative humidity in Urumqi was 57.5%.The relative humidity in winter was 77.5% which was the biggest all the year round,and the relative humidity in summer was 41.2% which was the smallest.The relative humidity in spring,summer,autumn,winter and the yearly relative humidity all displayed the increase trend.The yearly mean relative humidity had the periods of mainly 2,3-4 and quasi-7 years.The periodic oscillation of quasi-7 years was the strongest.
文摘In the context of climate change, the study of the variability of the climatic extremes in several regions of the world is of capital importance. This study has as main objective to analyze the variability of extreme temperature events in the Beninese basin of the Niger River for the recent and the near future. To achieve this objective, seven (07) extreme temperature indices based on historical daily temperature observations (1976 to 2019) and REMO RCM simulation outputs of RCP4.5 and RCP8.5 scenarios (2021-2050) were calculated. The obtained results were represented by calculating the means for each index and analyzing the trends and their significance by the Mann-Kendall method. The results show that the indices of extreme temperature intensity (TNn, TXx, and DTR), and those related to the frequency of warm sequences (WSDI, TN90p and TX90p) have experienced a significant increase in the past. This increase will continue until 2050. In contrast, the cold sequence frequency index (CSDI) decrease over the historical period as well as over the future period. These indices show much more change with the RCP8.5 scenario than with the RCP4.5 of the REMO climate model. Only the TXx and CSDI indices show statistically significant changes at all stations.
基金supported by the National Natural Science Foundation of China(Grant No.40233033)the Chinese Academy of Sciences(ZKCX2-SW-210 and KZCX2-203).
文摘Decadal/interdecadal climate variability is an important element in the CLIVAR (Climate Variability and Predictability) and has received much attention in the world. Many studies in relation to interdecadal variation have also been completed by Chinese scientists in recent years. In this paper, an introduction in outline for interdecadal climate variation research in China is presented. The content includes the features of interdecadal climate variability in China, global warming and interdecadal temperature variability, the NAO (the North Atlantic Oscillation)/NPO (the North Pacific Oscillation) and interdecadal climate variation in China, the interdecadal variation of the East Asian monsoon, the interdecadal mode of SSTA (Sea Surface Temperature Anomaly) in the North Pacific and its climate impact, and abrupt change feature of the climate.
基金jointly supported by the National Basic Research Program of China (Grant No. 2012CB 955301)the National Science Foundation of China (Grant Nos. 41175134 and 41305060)a China 111 project (Grant No. B13045)
文摘This study examines the expansion of drylands and regional climate change in northern China by analyzing the variations in aridity index （AI）, surface air temperature （SAT）, precipitation and potential evapotranspiration （PET） from 1948 to 2008. It is found that the drylands of northern China have expanded remarkably in the last 61 years. The area of drylands of the last 15 years （1994--2008） is 0.65 × 106 km2 （12%） larger than that in the period 1948-62. The boundary of drylands has extended eastward over Northeast China by about 2 °of longitude and by about 1° of latitude to the south along the middle- to-lower reaches of the Yellow River. A zonal band of expansion of semi-arid regions has occurred, stretching from western Heilongjiang Province to southern Gansu Province, while shifts to the east of semi-arid regions in dry subhumid regions have also occurred. Results show that the aridity trend of drylands in northern China is highly correlated with the long-term trend of precipitation and PET, and the expansion of semi-arid regions plays a dominant role in the areal extent of drylands, which is nearly 10 times larger than that in arid and subhumid regions.
基金This work was supported by National Key Basic Science Program in China !(G 1998040903)Chinese Academy of Science and the Nat
文摘This article discusses the interannual variation of the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO), its relationship with the interdecadal climate variation in China which is associated with the climate jump in the Northern Hemisphere in the 1960’s, using the data analyses. It is clearly shown that both the amplitudes of the NAO and NPO increase obviously in the 1960’s and the main period of the oscillations changes from 3-4 years before the 1960’s to 8–15 years after the 1960’s. Therefore, interdecadal climate variation in China or the climate jump in the 1960’s is closely related to the anomalies of the NAO and NPO. Key words North Atlantic Oscillation (NAO) - North Pacific Oscillation (NPO) - Climate Jump - Interdecadal climate variation This work was supported by National Key Basic Science Program in China (G1998040903), Chinese Academy of Science and the National Natural Science Fundation of China (Grant No.49823002).The authors are also grateful to Ms. Wang Xuan for typing the manuscript.
基金supported by the National Science Foundation of China (Grant No. 41271024)the Fund Project for National Basic Science Talents Cultivation (Grant No. J1210065)the Fundamental Research Funds for the Central Universities- Excellent Graduate Innovation Project (Grant No. Lzujbky-2014-274)
文摘Based on the 1990, 2000 and 2011 Landsat TM/ETM+ remote sensing data, glacier information of three periods in the Chinese Tianshan Mountains were extracted by using ratio threshold method(TM3/TM5) and visual interpretation, combined with digital processing of satellite images and analysis in GIS. The climate data in the surrounding area were analyzed by using linear regression, Mann-Kendall abrupt test, and Morlet wavelet analysis. Study results showed that: over the 23 years investigation, the glacier areas have markedly decreased. In the last 12 years(2000 to 2011), the rate of retreat has begun to accelerate. The most dramatic glacier shrinkage occurred in the central region, the lowest in the eastern region. The mean summer temperature and warm precipitation in Chinese Tianshan Mountains had an increasing trend, with rates of 0.22°C /10 a and 5.1mm/10 a from 1960 to 2011, respectively. Mean summer temperature have experienced a strong increase in 1998. The analysis of the results showed that the rise of mean summer temperature was the main factor that contributed to glacier shrinkage. Regional differences of glacier area changes were investigated by analyzing glacier behavior in five study sub-regions; regional differences are related to local climate, to the relative proportion of glaciers in different size classes, altitudinal and aspect distribution of glaciated areas. In addition, the lag theory indicated that glaciers may accelerate the retreat in the next decade, considering climate trends recognized for the period 2000-2011.
基金National Natural Sciences Foundation of China,No.41871021。
文摘Vegetation plays a key role in maintaining ecosystem stability,promoting biodiversity conservation,serving as windbreaks,and facilitating sand fixation in deserts.Based on the Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index(MODIS NDVI)and climate data,a Theil-Sen median trend analysis combined with the Mann-Kendall test and partial correlation and residual analyses were employed to explore spatiotemporal patterns of vegetation dynamics and key drivers in the Badain Jaran and Tengger deserts and Mu Us Sandy Land.Data were collected during the growing season between 2001 and 2020.Further analyses quantified the relative contribution of climate variation and anthropogenic activities to NDVI changes.Results revealed a predominantly increasing trend for average NDVI.The spread of average annual NDVI and growth trends of the vegetation were determined to be influenced by spatial differences.The area with improved vegetation was greater than that of the degraded region.Climate variability and human activities were driving forces controlling vegetation cover changes,and their effects on vegetation dynamics varied by region.The response of vegetation dynamics was stronger for precipitation than temperature,indicating that precipitation was the main climate variable influencing the NDVI changes.The relative role of human activities was responsible for>70%of the changes,demonstrating that human activities were the main driving factor of the NDVI changes.The implementation of ecological engineering is a key driver of increased vegetation coverage and has improved regional environmental quality.These results enhance our knowledge regarding NDVI change affected by climate variation and human activities and can provide future theoretical guidance for ecological restoration in arid areas.
基金The key project of Ministry of Science and Technology of China, No.2003DEA2C009-02
文摘The spatial distribution and monthly/annual variation of foggy days in China are analyzed based on the monthly mean fog data collected from 604 observational stations for the period 1961-2000. Results show that there are six fog regions in China： the middle reaches of the Yangtze River, coastal areas, Yunnan-Gulzhou Plateau, eastern Gansu-Shaanxi region, Huaihe River valley, Tianshan mountainous area and northern Xinjiang. On the whole the interannual variation trend of foggy days is descending, especially an obvious decline after the 1980s. The areas where the foggy days have obvious tendency present a southwest-northeast direction. The rising trend regions alternate with descending trend regions, forming a SE-NW directional wave structure. In general, the number of foggy days in autumn and winter is larger than in spring and summer over most fog regions. The monthly variation curves of foggy days are bimodal in the coastal area of the Yellow Sea and northern Xinjiang, and unimodal in other regions.
基金UNDP-supporting SPPD project !(Support for Policy Planning Development) Conducted in Ejin Horo Banner, Inner Mongolia
文摘A case study on the driving forces of desertification in the semi-arid region was carried out in the Ejin Horo Banner of Inner Mongolia. The occurrence and development of desertification were demonstrated and its driving factors were identified and analyzed. The results obtained indicated that over-reclamation of land overgrazing and denudation of natural vegetation cover were immediate and dominant factors causing land vulnerability to desertification. For a better understanding of the deep-rooted causes of the inappropriate land use and agricultural practices, the problems arising from various socioeconomic facets were comprehensively discussed.
