In the spring of 2021,southwestern China(SWC)experienced extreme drought,accompanied by the highest seasonal-mean temperature record since 1961.This drought event occurred in the decaying phase of a La Niña event...In the spring of 2021,southwestern China(SWC)experienced extreme drought,accompanied by the highest seasonal-mean temperature record since 1961.This drought event occurred in the decaying phase of a La Niña event with negative geopotential height anomalies over the Philippine Sea,which is distinct from the historical perspective.Historically,spring drought over SWC is often linked to El Niño and strong western North Pacific subtropical high.Here,we show that the extreme drought in the spring of 2021 may be mainly driven by the atmospheric internal variability and amplified by the warming trend.Specifically,the evaporation increase due to the high temperature accounts for about 30%of drought severity,with the contributions of its linear trend portion being nearly 20%and the interannual variability portion being about 10%.Since the sea surface temperature forcing from the tropical central and eastern Pacific played a minor role in the occurrence of drought,it is a challenge for a climate model to capture the 2021 SWC drought beyond one-month lead times.展开更多
Daily precipitation data from 149 rain gauge stations in China and NCEP-NCAR reanalysis data during 1961-2018are used to investigate the interdecadal variability of summer precipitation in Northwest China and related ...Daily precipitation data from 149 rain gauge stations in China and NCEP-NCAR reanalysis data during 1961-2018are used to investigate the interdecadal variability of summer precipitation in Northwest China and related causes.The results suggest that,on the interdecadal timescale,Northwest China shifts into a rainy period from the year 1987,with an increase in the precipitation amount and intensity;an increase in the probability of moderate rain,heavy rain,torrential rain,and extremely heavy rain;and a decrease in the probability of light rain.More than 60%of the increase in precipitation can be attributed to rainfall with intensity above the grade of heavy rain.The associated interdecadal variability of atmospheric circulations over midlatitude Eurasia in summer is examined and it is found that the interdecadal variability is mainly characterized by the Silk Road pattern(SRP),with a cyclonic circulation anomaly and an anticyclonic circulation anomaly over central Asia and Mongolia,respectively;enhanced ascending motion and atmospheric instability in Northwest China;and strengthened easterly winds caused by the Mongolian anticyclonic anomaly along the northern boundary of the Tibetan Plateau.On the south side of the Mongolian anticyclone,the water vapor transported from the Pacific and Indian Oceans as well as the South China Sea to Northwest China by easterly winds increases significantly,providing the main water vapor source for the increase in precipitation in Northwest China on the interdecadal timescale.The transition of the Atlantic multidecadal oscillation to a positive phase may be the main cause of the interdecadal transition of the SRP to a positive phase,resulting in the interdecadal increase in summer precipitation in Northwest China.展开更多
基金supported by the National Key R&D Program of China(Grant No.2017YFA0605004)Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030004)+2 种基金National Natural Science Foundations of China(Grant No.42175056)the China Meteorological Administration Innovation and Development Project(CXFZ2022J031)the Joint Open Project of KLME&CIC-FEMD,NUIST(Grant No.KLME202102).
文摘In the spring of 2021,southwestern China(SWC)experienced extreme drought,accompanied by the highest seasonal-mean temperature record since 1961.This drought event occurred in the decaying phase of a La Niña event with negative geopotential height anomalies over the Philippine Sea,which is distinct from the historical perspective.Historically,spring drought over SWC is often linked to El Niño and strong western North Pacific subtropical high.Here,we show that the extreme drought in the spring of 2021 may be mainly driven by the atmospheric internal variability and amplified by the warming trend.Specifically,the evaporation increase due to the high temperature accounts for about 30%of drought severity,with the contributions of its linear trend portion being nearly 20%and the interannual variability portion being about 10%.Since the sea surface temperature forcing from the tropical central and eastern Pacific played a minor role in the occurrence of drought,it is a challenge for a climate model to capture the 2021 SWC drought beyond one-month lead times.
基金Supported by the National Key Research and Development Program of China (2017YFA0605004)National Natural Science Foundation of China (41775082 and 41975100)。
文摘Daily precipitation data from 149 rain gauge stations in China and NCEP-NCAR reanalysis data during 1961-2018are used to investigate the interdecadal variability of summer precipitation in Northwest China and related causes.The results suggest that,on the interdecadal timescale,Northwest China shifts into a rainy period from the year 1987,with an increase in the precipitation amount and intensity;an increase in the probability of moderate rain,heavy rain,torrential rain,and extremely heavy rain;and a decrease in the probability of light rain.More than 60%of the increase in precipitation can be attributed to rainfall with intensity above the grade of heavy rain.The associated interdecadal variability of atmospheric circulations over midlatitude Eurasia in summer is examined and it is found that the interdecadal variability is mainly characterized by the Silk Road pattern(SRP),with a cyclonic circulation anomaly and an anticyclonic circulation anomaly over central Asia and Mongolia,respectively;enhanced ascending motion and atmospheric instability in Northwest China;and strengthened easterly winds caused by the Mongolian anticyclonic anomaly along the northern boundary of the Tibetan Plateau.On the south side of the Mongolian anticyclone,the water vapor transported from the Pacific and Indian Oceans as well as the South China Sea to Northwest China by easterly winds increases significantly,providing the main water vapor source for the increase in precipitation in Northwest China on the interdecadal timescale.The transition of the Atlantic multidecadal oscillation to a positive phase may be the main cause of the interdecadal transition of the SRP to a positive phase,resulting in the interdecadal increase in summer precipitation in Northwest China.