Climate change is one of the most important factors that affect vegetation distribution in North China. Among all climatic factors, drought is considered to have the most significant effect on the environment. Based o...Climate change is one of the most important factors that affect vegetation distribution in North China. Among all climatic factors, drought is considered to have the most significant effect on the environment. Based on previous studies, the climate drought index can be used to assess the evolutionary trend of the ecological environment under various arid climatic conditions. It is necessary for us to further explore the relationship between vegetation coverage（index） and climate drought conditions. Therefore, in this study, based on MODIS-NDVI products and meteorological observation data, the Palmer Drought Severity Index（PDSI） and vegetation coverage in North China were first calculated. Then, the interannual variations of PDSI and vegetation coverage during 2001–2013 were analyzed using a Theil-Sen slope estimator. Finally, an ecoregion perspective of the correlation between them was discussed. The experimental results demonstrated that the PDSI index and vegetation coverage value varied over different ecoregions. During the period 2001–2013, vegetation coverage increased in the southern and northern mountains of North China, while it showed a decreasing trend in the Beijing-Tianjin-Tangshan City Circle area and suburban agricultural zone located in Hebei Province and Henan Province）. Over 13 years, the climate of the northeastern part of North China became more humid, while in the southern part of North China, it tended to be dry. According to the correlation analysis results, 73.37% of North China showed a positive correlation between the vegetation coverage and climate drought index. A negative correlation was observed mainly in urban and suburban areas of Beijing, Tianjin, Hebei Province, and Henan Province. In most parts of North China, drought conditions in summer and autumn had a strong influence on vegetation coverage.展开更多
Monthly data of Self-Calibrated Palmer Drought Severity Index (PDSI) from 1951 to 2000 are calculated using historical precipitation and temperature data for Chinese 160 stations. Temporal and spatial pat-terns of the...Monthly data of Self-Calibrated Palmer Drought Severity Index (PDSI) from 1951 to 2000 are calculated using historical precipitation and temperature data for Chinese 160 stations. Temporal and spatial pat-terns of the first empirical orthogonal function (EOF) of the PDSI reveals a fairly linear trend resulting from trends in precipitation and surface temperature, which is similar to the linear PDSI trend during 1951―2000 calculated using all monthly data. The EOF analysis also reveals that the leading mode correlates significantly with ENSO events in time and space. The ENSO EOF shows that during the typical warm phase of ENSO, surface conditions are drier in most regions of China, especially North China, but wetter than normal in the southern regions of Changjiang River, and Northwest China. During the typical cold phase of ENSO, these anomalies reverse sign. From 1951 to 2000, there are large multi-year to decadal variations in droughts and wet spells over China, which are all closely related to strong El Nio events. In other words, when one strong El Nio event happens, there is a possible big variability in droughts and wet spells over China on the multi-year or decadal scale. Studies also sug-gest that during the last 2―3 decades climate changes over China, especially North China's drying and northwest China's wetting, are closely related to the shift in ENSO towards warmer events and global warming since the late 1970s. The instability of the relationship is also studied. It is revealed that there is a good correlation between ENSO and Chinese variations in droughts and wet spells in the 3―8-year band, but the correlation between ENSO and Chinese variations in droughts and wet spells is instable. Studies suggest that there are decadal changes in the correlation: the wavelet coherency between ENSO and Chinese variations in droughts and wet spells is high during 1951―1962 and 1976―1991, but low during 1963―1975 and 1992―2000.展开更多
以渭河流域为例,从流域水文循环的角度出发,在SWAT(Soil and Water Assessment Tool)分布式水文模型和Palmer干旱指数(Palmer Drought Severity Index)原理的基础上提出了干旱分析模型SWAT-PDSI,对渭河流域干旱的时空演变规律和发生频...以渭河流域为例,从流域水文循环的角度出发,在SWAT(Soil and Water Assessment Tool)分布式水文模型和Palmer干旱指数(Palmer Drought Severity Index)原理的基础上提出了干旱分析模型SWAT-PDSI,对渭河流域干旱的时空演变规律和发生频率进行了分析。研究结果表明:1经率定和验证的SWAT模型能够较好地模拟渭河流域的水文变化过程;2利用SWAT-PDSI对典型干旱事件(1995年干旱)的评估结果显示,该模型能较好地反映渭河流域干旱的时空差异和变化规律;3渭河流域、渭河干流和泾河流域均表现为变干的趋势,而北洛河流域表现为变湿的趋势,但均未通过95%的置信水平检验;4渭河流域多数子流域的SWAT-PDSI多年平均值处于-1~1,说明该流域多数地区处于正常状态;5渭河流域北部的北洛河流域和泾河流域的上游地区易发生干旱,发生中等以上、严重以上和极端干旱事件的频率最高。展开更多
Northwest China is one of the most arid regions in the world and has experienced intriguing climate warming and humidification.Nonetheless,future climate conditions in Northwest China still remain uncertain.In this st...Northwest China is one of the most arid regions in the world and has experienced intriguing climate warming and humidification.Nonetheless,future climate conditions in Northwest China still remain uncertain.In this study,we applied an ensemble of the 12 latest model simulations of the Coupled Model Intercomparison Project Phase 6(CMIP6)to assess future drought conditions until 2099 in Northwest China,as inferred from the Palmer Drought Severity Index(PDSI).Future drought conditions were projected under three climate change scenarios through the combination of shared socioeconomic pathways(SSPs)and representative concentration pathways(RCPs),namely,SSP126(SSP1+RCP2.6,a green development pathway),SSP245(SSP2+RCP4.5,an intermediate development pathway),and SSP585(SSP5+RCP8.5,a high development pathway).For 2015-2099,drought severity showed no trend under SSP126,in contrast,for the SSP245 and SSP585 scenarios,a rapid increase during 2015-2099 was observed,especially under SSP585.We also found that the drought frequency in Northwest China under SSP585 was generally lower than that under SSP126 and SSP245,although the drought duration under SSP585 tended to be longer.These findings suggest the green development pathway in drought mitigation and adaptation strategies in Northwest China,an arid and agricultural region along the Silk Road.展开更多
基金International Science & Technology Cooperation Program of China,No.2014DFA21620The China Scholarship Fund
文摘Climate change is one of the most important factors that affect vegetation distribution in North China. Among all climatic factors, drought is considered to have the most significant effect on the environment. Based on previous studies, the climate drought index can be used to assess the evolutionary trend of the ecological environment under various arid climatic conditions. It is necessary for us to further explore the relationship between vegetation coverage（index） and climate drought conditions. Therefore, in this study, based on MODIS-NDVI products and meteorological observation data, the Palmer Drought Severity Index（PDSI） and vegetation coverage in North China were first calculated. Then, the interannual variations of PDSI and vegetation coverage during 2001–2013 were analyzed using a Theil-Sen slope estimator. Finally, an ecoregion perspective of the correlation between them was discussed. The experimental results demonstrated that the PDSI index and vegetation coverage value varied over different ecoregions. During the period 2001–2013, vegetation coverage increased in the southern and northern mountains of North China, while it showed a decreasing trend in the Beijing-Tianjin-Tangshan City Circle area and suburban agricultural zone located in Hebei Province and Henan Province）. Over 13 years, the climate of the northeastern part of North China became more humid, while in the southern part of North China, it tended to be dry. According to the correlation analysis results, 73.37% of North China showed a positive correlation between the vegetation coverage and climate drought index. A negative correlation was observed mainly in urban and suburban areas of Beijing, Tianjin, Hebei Province, and Henan Province. In most parts of North China, drought conditions in summer and autumn had a strong influence on vegetation coverage.
基金Supported by the Key Program of the Chinese Academy of Sciences (Grant No. KZCX3-SW-221)the National Natural Science Foundation of China (Grant No. 40475037)
文摘Monthly data of Self-Calibrated Palmer Drought Severity Index (PDSI) from 1951 to 2000 are calculated using historical precipitation and temperature data for Chinese 160 stations. Temporal and spatial pat-terns of the first empirical orthogonal function (EOF) of the PDSI reveals a fairly linear trend resulting from trends in precipitation and surface temperature, which is similar to the linear PDSI trend during 1951―2000 calculated using all monthly data. The EOF analysis also reveals that the leading mode correlates significantly with ENSO events in time and space. The ENSO EOF shows that during the typical warm phase of ENSO, surface conditions are drier in most regions of China, especially North China, but wetter than normal in the southern regions of Changjiang River, and Northwest China. During the typical cold phase of ENSO, these anomalies reverse sign. From 1951 to 2000, there are large multi-year to decadal variations in droughts and wet spells over China, which are all closely related to strong El Nio events. In other words, when one strong El Nio event happens, there is a possible big variability in droughts and wet spells over China on the multi-year or decadal scale. Studies also sug-gest that during the last 2―3 decades climate changes over China, especially North China's drying and northwest China's wetting, are closely related to the shift in ENSO towards warmer events and global warming since the late 1970s. The instability of the relationship is also studied. It is revealed that there is a good correlation between ENSO and Chinese variations in droughts and wet spells in the 3―8-year band, but the correlation between ENSO and Chinese variations in droughts and wet spells is instable. Studies suggest that there are decadal changes in the correlation: the wavelet coherency between ENSO and Chinese variations in droughts and wet spells is high during 1951―1962 and 1976―1991, but low during 1963―1975 and 1992―2000.
文摘以渭河流域为例,从流域水文循环的角度出发,在SWAT(Soil and Water Assessment Tool)分布式水文模型和Palmer干旱指数(Palmer Drought Severity Index)原理的基础上提出了干旱分析模型SWAT-PDSI,对渭河流域干旱的时空演变规律和发生频率进行了分析。研究结果表明:1经率定和验证的SWAT模型能够较好地模拟渭河流域的水文变化过程;2利用SWAT-PDSI对典型干旱事件(1995年干旱)的评估结果显示,该模型能较好地反映渭河流域干旱的时空差异和变化规律;3渭河流域、渭河干流和泾河流域均表现为变干的趋势,而北洛河流域表现为变湿的趋势,但均未通过95%的置信水平检验;4渭河流域多数子流域的SWAT-PDSI多年平均值处于-1~1,说明该流域多数地区处于正常状态;5渭河流域北部的北洛河流域和泾河流域的上游地区易发生干旱,发生中等以上、严重以上和极端干旱事件的频率最高。
基金financially supported by the National Key Research and Development Program of China(2017YFA0603804)the Key Project of National Social and Scientific Fund Program(16ZDA047)+2 种基金the European Union's Framework Programme for Research and Innovation Horizon 2020(2014—2020)under the Marie Sklodowska-Curie Agreement(795179)the Alexander von Humboldt Foundation of GermanyPostgraduate Research&Practice Innovation Program of Jiangsu Province(SJKY19_0961).
文摘Northwest China is one of the most arid regions in the world and has experienced intriguing climate warming and humidification.Nonetheless,future climate conditions in Northwest China still remain uncertain.In this study,we applied an ensemble of the 12 latest model simulations of the Coupled Model Intercomparison Project Phase 6(CMIP6)to assess future drought conditions until 2099 in Northwest China,as inferred from the Palmer Drought Severity Index(PDSI).Future drought conditions were projected under three climate change scenarios through the combination of shared socioeconomic pathways(SSPs)and representative concentration pathways(RCPs),namely,SSP126(SSP1+RCP2.6,a green development pathway),SSP245(SSP2+RCP4.5,an intermediate development pathway),and SSP585(SSP5+RCP8.5,a high development pathway).For 2015-2099,drought severity showed no trend under SSP126,in contrast,for the SSP245 and SSP585 scenarios,a rapid increase during 2015-2099 was observed,especially under SSP585.We also found that the drought frequency in Northwest China under SSP585 was generally lower than that under SSP126 and SSP245,although the drought duration under SSP585 tended to be longer.These findings suggest the green development pathway in drought mitigation and adaptation strategies in Northwest China,an arid and agricultural region along the Silk Road.
