Various investigations have been conducted to analyze the water-coverage area of the Aral Sea and the Aral Sea Basin(ASB). However, the investigations incorporated considerable uncertainty and the used water indices h...Various investigations have been conducted to analyze the water-coverage area of the Aral Sea and the Aral Sea Basin(ASB). However, the investigations incorporated considerable uncertainty and the used water indices had misclassification problem, which made different research groups present different results. Thus we first ascertain the boundaries of the ASB, the Syr and Amu river basins as well as their upper, middle and lower reaches. Then a four-band index for both liquid and solid water(ILSW) is proposed to address the misclassification problems of the classic water indices. ILSW is calculated by using the reflectance values of the green, red, near infrared, and thermal infrared bands, which combines the normalized difference water index(NDWI) and land surface temperature(LST) together. Validation results show that the ILSW water index has the highest accuracy by far in the Aral Sea Basin. Our results indicate that annual average decline of the water-coverage area was 963 km^(2) in the southern Aral Sea, whereas the northern Aral Sea has experienced little change. In the meanwhile, permanent ice and snow in upper reach of ASB has retreated considerably. Annual retreating rates of the permanent ice and snow were respectively 6233and 3841 km^(2) in upper reaches of Amu river basin(UARB) and Syr river basin(USRB). One of major reasons is that climate has become warmer in ASB. The climate change has caused serious water deficit problem. The water deficit had an increasing trend since the 1990s and its increasing rates was 3.778 billion m^(3) yearly on average. The total water deficit was 76.967 billion m^(3) on average in the whole area of ASB in the 2010s. However, up reaches of Syr river basin(USRB), a component area of ASB, had water surplus of 25.461 billion m^(3). These conclusions are useful for setting out a sustainable development strategy in ASB.展开更多
基于CRU(Climate Research Unit)数据集1945—2019年咸海流域月降水序列,利用气候倾向率、集中度与分摊熵、样本熵与排列熵方法,分别分析了咸海流域年降水量变化、降水的年内分配、降水序列复杂性变化的时空特征,并用Mann-Kendall法检...基于CRU(Climate Research Unit)数据集1945—2019年咸海流域月降水序列,利用气候倾向率、集中度与分摊熵、样本熵与排列熵方法,分别分析了咸海流域年降水量变化、降水的年内分配、降水序列复杂性变化的时空特征,并用Mann-Kendall法检验了各方法所得结果的趋势性。结果表明:咸海流域年降水量总体基本保持不变,呈微弱的上升趋势,其中,流域西北部及中东部区域降水量呈显著上升的趋势;咸海流域降水集中于每年的3月左右,降水的年内分配有微弱的均匀化趋势,流域西部、北部及东部降水年内分配相对更均匀,流域中部及南部降水年内分配相对更集中;咸海流域西部、北部及东部降水序列的复杂性相对较高,中部及南部降水序列的复杂性相对较低,流域整体的降水序列的复杂性呈一定的上升趋势,其中,流域北部与南部降水序列的复杂性呈显著下降的趋势,流域西部、中部与东部降水序列的复杂性呈显著上升的趋势。展开更多
In the context of global climate warming,the propagation of meteorological drought(MD)may aggravate the devastating impact of hydrological drought(HD)on water security and sustainable development.There are challenges ...In the context of global climate warming,the propagation of meteorological drought(MD)may aggravate the devastating impact of hydrological drought(HD)on water security and sustainable development.There are challenges in accurately predicting the propagation of drought and effectively quantifying the effects of uncertainty,especially in data-deficient regions.In this study,a novel method called RFCFA is developed through integrating random forest(RF),copula,and factorial analysis(FA)into a general framework as well as applied to the Aral Sea Basin(a typical arid and data-scarce basin in Central Asia)under considering the impact of climate change.Several findings can be summarized:(1)the projected future drought propagation probability of ASB is 39.2%,which is about 8%higher than historical level;(2)drought propagation is mainly affected by mean climate condition,catchment characteristics(i.e.,elevation,LUCC,and slope),and human activities(i.e.,irrigation and reservoir operation);(3)the lower propagation probability in spring is expected under SSP1-2.6 due to increased snow meltwater,and the drought propagation probability in autumn is the highest(reaching 45.4%)under the influence of reservoir operation;(4)the combined effects of meteorological conditions and agricultural irrigation can lead to a higher probability of future propagation in the upper river basin in summer.Findings are valuable for predicting drought propagation risk,revealing main factors and inherent uncertainties,as well as providing support for drought management and disaster prevention.展开更多
基金supported by the Key Program of National Natural Science Foundation of China(Grant No.42230708)the Strategic Priority Research Program of the Chinese Academy of Sciences,Pan-Third Pole Environment Study for a Green Silk Road(Grant No.XDA20060303)the K.C.Wong Education Foundation(Grant No.GJTD-2020-14)。
文摘Various investigations have been conducted to analyze the water-coverage area of the Aral Sea and the Aral Sea Basin(ASB). However, the investigations incorporated considerable uncertainty and the used water indices had misclassification problem, which made different research groups present different results. Thus we first ascertain the boundaries of the ASB, the Syr and Amu river basins as well as their upper, middle and lower reaches. Then a four-band index for both liquid and solid water(ILSW) is proposed to address the misclassification problems of the classic water indices. ILSW is calculated by using the reflectance values of the green, red, near infrared, and thermal infrared bands, which combines the normalized difference water index(NDWI) and land surface temperature(LST) together. Validation results show that the ILSW water index has the highest accuracy by far in the Aral Sea Basin. Our results indicate that annual average decline of the water-coverage area was 963 km^(2) in the southern Aral Sea, whereas the northern Aral Sea has experienced little change. In the meanwhile, permanent ice and snow in upper reach of ASB has retreated considerably. Annual retreating rates of the permanent ice and snow were respectively 6233and 3841 km^(2) in upper reaches of Amu river basin(UARB) and Syr river basin(USRB). One of major reasons is that climate has become warmer in ASB. The climate change has caused serious water deficit problem. The water deficit had an increasing trend since the 1990s and its increasing rates was 3.778 billion m^(3) yearly on average. The total water deficit was 76.967 billion m^(3) on average in the whole area of ASB in the 2010s. However, up reaches of Syr river basin(USRB), a component area of ASB, had water surplus of 25.461 billion m^(3). These conclusions are useful for setting out a sustainable development strategy in ASB.
文摘基于CRU(Climate Research Unit)数据集1945—2019年咸海流域月降水序列,利用气候倾向率、集中度与分摊熵、样本熵与排列熵方法,分别分析了咸海流域年降水量变化、降水的年内分配、降水序列复杂性变化的时空特征,并用Mann-Kendall法检验了各方法所得结果的趋势性。结果表明:咸海流域年降水量总体基本保持不变,呈微弱的上升趋势,其中,流域西北部及中东部区域降水量呈显著上升的趋势;咸海流域降水集中于每年的3月左右,降水的年内分配有微弱的均匀化趋势,流域西部、北部及东部降水年内分配相对更均匀,流域中部及南部降水年内分配相对更集中;咸海流域西部、北部及东部降水序列的复杂性相对较高,中部及南部降水序列的复杂性相对较低,流域整体的降水序列的复杂性呈一定的上升趋势,其中,流域北部与南部降水序列的复杂性呈显著下降的趋势,流域西部、中部与东部降水序列的复杂性呈显著上升的趋势。
基金supported by the Innovative Research Group of the National Natural Science Foundation of China(52221003)the Strategic Priority Research Program of Chinese Academy of Sciences(XDA20060302)the National Natural Science Foundation of China(52279003 and 52279002)
文摘In the context of global climate warming,the propagation of meteorological drought(MD)may aggravate the devastating impact of hydrological drought(HD)on water security and sustainable development.There are challenges in accurately predicting the propagation of drought and effectively quantifying the effects of uncertainty,especially in data-deficient regions.In this study,a novel method called RFCFA is developed through integrating random forest(RF),copula,and factorial analysis(FA)into a general framework as well as applied to the Aral Sea Basin(a typical arid and data-scarce basin in Central Asia)under considering the impact of climate change.Several findings can be summarized:(1)the projected future drought propagation probability of ASB is 39.2%,which is about 8%higher than historical level;(2)drought propagation is mainly affected by mean climate condition,catchment characteristics(i.e.,elevation,LUCC,and slope),and human activities(i.e.,irrigation and reservoir operation);(3)the lower propagation probability in spring is expected under SSP1-2.6 due to increased snow meltwater,and the drought propagation probability in autumn is the highest(reaching 45.4%)under the influence of reservoir operation;(4)the combined effects of meteorological conditions and agricultural irrigation can lead to a higher probability of future propagation in the upper river basin in summer.Findings are valuable for predicting drought propagation risk,revealing main factors and inherent uncertainties,as well as providing support for drought management and disaster prevention.
