In this study, the seasonal transition of precipitation over the middle and lower reaches of the Yang-tze River Valley (YRV) from late spring to early summer is investigated. The results show that the seasonal transit...In this study, the seasonal transition of precipitation over the middle and lower reaches of the Yang-tze River Valley (YRV) from late spring to early summer is investigated. The results show that the seasonal transition of precipitation exhibits multi-modes. One of these modes is characterized by an abrupt transition from drought to flood (ATDF) over the middle and lower reaches of the YRV in the seasonal transition of precipitation. It is shown that the ATDF event from May to June 2011 is simply one prominent case of the ATDF mode. The ATDF mode exhibits an obvious decadal variability. The mode has occurred more frequently since 1979, and its amplitude has apparently strengthened since 1994. From the climatic view, the ATDF mode configures a typical seasonal circulation transition from winter to summer, for which the winter circulations are prolonged, and the summer circulations with the rainy season are built up early over the YRV.展开更多
It has been shown by the observed data that during the early 1990′s, the severe disastrous climate occurred in East Asia. In the summer of 1991, severe flood occurred in the Yangtze River and the Huaihe River basin o...It has been shown by the observed data that during the early 1990′s, the severe disastrous climate occurred in East Asia. In the summer of 1991, severe flood occurred in the Yangtze River and the Huaihe River basin of China and in South Korea, and it also appeared in South Korea in the summer of 1993. However, in the summer of 1994, a dry and hot summer was caused in the Huaihe River basin of China and in R. O. K.. In order to investigate the seasonal predictability of the summer droughts and floods during the early 1990′s in East Asia, the seasonal prediction experiments of the summer droughts and floods in the summers of 1991-1994 in East Asia have been made by using the Institute of Atmopsheric Physics-Two-Level General Circulation Model (IAP-L2 AGCM), the IAP-Atmosphere/Ocean Coupled Model (IAP-CGCM) and the IAP-L2 AGCM including a filtering scheme, respectively. Compared with the observational facts, it is shown that the IAP-L2 AGCM or IAP-CGCM has some predictability for the summer droughts and floods during the early 1990′s in East Asia, especially for the severe droughts and floods in China and R. O. K.. In this study, a filtering scheme is used to improve the seasonal prediction experiments of the summer droughts and floods during the early 1990′s in East Asia. The predicted results show that the filtering scheme to remain the planetary-scale disturbances is an effective method for the improvement of the seasonal prediction of the summer droughts and floods in East Asia.展开更多
[Objective]The research aimed to analyze precipitation change and agricultural drought and flood degrees during crop growth season in Binzhou.[Method]Based on monthly rainfall and average temperature data at Binzhou m...[Objective]The research aimed to analyze precipitation change and agricultural drought and flood degrees during crop growth season in Binzhou.[Method]Based on monthly rainfall and average temperature data at Binzhou meteorological observatory during March-November of1981-2010,by using linear regression,climatic tendency rate and dry-wet coefficient,precipitation change and agricultural drought and flood degrees during crop growth season of the past 30 years in Binzhou were analyzed from natural precipitation tendency change and satisfaction degree of agricultural water demand during crop growth season.[Result]In the past 30 years,precipitation during growth season in Binzhou presented increasing tendency.Spring,summer and autumn precipitation all increased somewhat,especially summer precipitation.Monthly average rainfall distribution was very uneven,and rainfall in July and August was more.In the past 30 years,average dry-wet coefficient K value during crop growth season in Binzhou was 0.60,it overall belonged to moderate drought climate type,and occurrence frequency of drought was 97%.It belonged to serious drought climate type in spring and autumn and light drought climate type in summer.Dry-wet coefficient presented rising tendency,illustrating that climate was developing toward wet direction.Seen from mean over the years,except humid in July,it was over light drought in other months.[Conclusion]Climate was overall arid during crop growth season in Binzhou,but precipitation somewhat increased in the past 30 years.Therefore,we suggested that artificial rainfall work should be enhanced.展开更多
Based on monthly precipitation data during 1961-2008 in 50 stations in Fushun,drought and flood indicators of three counties were calculated with Z index method. The geographical and seasonal distribution characterist...Based on monthly precipitation data during 1961-2008 in 50 stations in Fushun,drought and flood indicators of three counties were calculated with Z index method. The geographical and seasonal distribution characteristics of Fushun were analyzed,and so was the impact of droughts and floods on food production. It shows that,since 1961,there are 7 poor harvest years in Fushun,with quadrennial caused by continuous seasonal floods or droughts,two years by year drought,one year by summer flood.展开更多
In spring and early summer of 2019, Yunnan Province experienced the most severe seasonal drought on record,with days of extreme drought area exceeding 10^5 km^2 far more than normal. Consistently, the precipitation in...In spring and early summer of 2019, Yunnan Province experienced the most severe seasonal drought on record,with days of extreme drought area exceeding 10^5 km^2 far more than normal. Consistently, the precipitation in each month from February to June is over 30% less than normal, and about 50% less in the most severe drought period(April–June). The rainy season in Southwest China(SWC) started on the third pentad in June 2019, which is the second latest in history. The rainy season in Yunnan started on 24 June, which is the latest(29 days later than normal). On the contrary, the onset of the South China Sea summer monsoon(SCSSM) is abnormally early. The lag time between the start of the rainy season in SWC and the onset of the SCSSM in 2019 is 7 pentads, which is the largest since 1961, much longer than the climate mean(less than 1 pentad). The present study analyzes the possible reasons why the rainy season came extremely late and the drought disaster persisted and intensified after a much early SCSSM, at both seasonal and subseasonal timescales. The abnormally late onset of the rainy season and the second greatest potential evapotranspiration(PET) since 1981 are the direct reasons for the persistent drought. Statistical results show that the water vapor from southwest of Yunnan in April–June contributes more than that from the east at the seasonal scale. In April–June 2019, however, the southern branch trough(SBT) was abnormally weak, the large and strong anticyclonic wind anomaly prevailed over the Bay of the Bengal(BOB), and the meridional water vapor transport to Yunnan was weak. At the subseasonal scale, the weaker SBT lasted the longest, and the strong convection over the BOB came up late despite of an early onset of the SCSSM, which resulted in reduced low-level moisture convergence in Yunnan and development of drought prior to the SCSSM onset. From the onset of SCSSM to the start of rainy season in SWC, the SBT and meridional water vapor transport from the BOB were still weak, and the water vapor was mainly transported into the coastal area of South and Southeast China rather than Yunnan. After the start of the rainy season in SWC, the SBT was still weak. This led to less moisture transport in the westerlies to the west of Yunnan and the persistent extreme drought. Both the statistical results and case analysis indicate that the stronger Australian high in spring and early summer of 2019 was associated with the abnormally strong anticyclone over the BOB and the always weak SBT. In sum, the anomalous weakness of SBT played a critical role in the extreme drought occurrence and persistence in Yunnan of Southwest China in 2019.展开更多
基金supported by the National Basic Research Program of China (Grant No.2009CB421401)the National Key Technologies R&D Program of China (Grant No. 2009BAC51B02)+1 种基金the National Natural Science Foundation of China (Grant No. 40975022)the Special Scien-tific Research Fund of the Meteorological Public Welfare Profession of China (Grant No. GYHY200906018)
文摘In this study, the seasonal transition of precipitation over the middle and lower reaches of the Yang-tze River Valley (YRV) from late spring to early summer is investigated. The results show that the seasonal transition of precipitation exhibits multi-modes. One of these modes is characterized by an abrupt transition from drought to flood (ATDF) over the middle and lower reaches of the YRV in the seasonal transition of precipitation. It is shown that the ATDF event from May to June 2011 is simply one prominent case of the ATDF mode. The ATDF mode exhibits an obvious decadal variability. The mode has occurred more frequently since 1979, and its amplitude has apparently strengthened since 1994. From the climatic view, the ATDF mode configures a typical seasonal circulation transition from winter to summer, for which the winter circulations are prolonged, and the summer circulations with the rainy season are built up early over the YRV.
文摘It has been shown by the observed data that during the early 1990′s, the severe disastrous climate occurred in East Asia. In the summer of 1991, severe flood occurred in the Yangtze River and the Huaihe River basin of China and in South Korea, and it also appeared in South Korea in the summer of 1993. However, in the summer of 1994, a dry and hot summer was caused in the Huaihe River basin of China and in R. O. K.. In order to investigate the seasonal predictability of the summer droughts and floods during the early 1990′s in East Asia, the seasonal prediction experiments of the summer droughts and floods in the summers of 1991-1994 in East Asia have been made by using the Institute of Atmopsheric Physics-Two-Level General Circulation Model (IAP-L2 AGCM), the IAP-Atmosphere/Ocean Coupled Model (IAP-CGCM) and the IAP-L2 AGCM including a filtering scheme, respectively. Compared with the observational facts, it is shown that the IAP-L2 AGCM or IAP-CGCM has some predictability for the summer droughts and floods during the early 1990′s in East Asia, especially for the severe droughts and floods in China and R. O. K.. In this study, a filtering scheme is used to improve the seasonal prediction experiments of the summer droughts and floods during the early 1990′s in East Asia. The predicted results show that the filtering scheme to remain the planetary-scale disturbances is an effective method for the improvement of the seasonal prediction of the summer droughts and floods in East Asia.
文摘[Objective]The research aimed to analyze precipitation change and agricultural drought and flood degrees during crop growth season in Binzhou.[Method]Based on monthly rainfall and average temperature data at Binzhou meteorological observatory during March-November of1981-2010,by using linear regression,climatic tendency rate and dry-wet coefficient,precipitation change and agricultural drought and flood degrees during crop growth season of the past 30 years in Binzhou were analyzed from natural precipitation tendency change and satisfaction degree of agricultural water demand during crop growth season.[Result]In the past 30 years,precipitation during growth season in Binzhou presented increasing tendency.Spring,summer and autumn precipitation all increased somewhat,especially summer precipitation.Monthly average rainfall distribution was very uneven,and rainfall in July and August was more.In the past 30 years,average dry-wet coefficient K value during crop growth season in Binzhou was 0.60,it overall belonged to moderate drought climate type,and occurrence frequency of drought was 97%.It belonged to serious drought climate type in spring and autumn and light drought climate type in summer.Dry-wet coefficient presented rising tendency,illustrating that climate was developing toward wet direction.Seen from mean over the years,except humid in July,it was over light drought in other months.[Conclusion]Climate was overall arid during crop growth season in Binzhou,but precipitation somewhat increased in the past 30 years.Therefore,we suggested that artificial rainfall work should be enhanced.
基金Supported by Fushun Government Financed Subject(20071209)
文摘Based on monthly precipitation data during 1961-2008 in 50 stations in Fushun,drought and flood indicators of three counties were calculated with Z index method. The geographical and seasonal distribution characteristics of Fushun were analyzed,and so was the impact of droughts and floods on food production. It shows that,since 1961,there are 7 poor harvest years in Fushun,with quadrennial caused by continuous seasonal floods or droughts,two years by year drought,one year by summer flood.
基金Supported by the National Key Research and Development Program of China(2018YFC1505603 and 2017YFC1502402)China Meteorological Administration Special Public Welfare Research Fund(GYHY201306033)。
文摘In spring and early summer of 2019, Yunnan Province experienced the most severe seasonal drought on record,with days of extreme drought area exceeding 10^5 km^2 far more than normal. Consistently, the precipitation in each month from February to June is over 30% less than normal, and about 50% less in the most severe drought period(April–June). The rainy season in Southwest China(SWC) started on the third pentad in June 2019, which is the second latest in history. The rainy season in Yunnan started on 24 June, which is the latest(29 days later than normal). On the contrary, the onset of the South China Sea summer monsoon(SCSSM) is abnormally early. The lag time between the start of the rainy season in SWC and the onset of the SCSSM in 2019 is 7 pentads, which is the largest since 1961, much longer than the climate mean(less than 1 pentad). The present study analyzes the possible reasons why the rainy season came extremely late and the drought disaster persisted and intensified after a much early SCSSM, at both seasonal and subseasonal timescales. The abnormally late onset of the rainy season and the second greatest potential evapotranspiration(PET) since 1981 are the direct reasons for the persistent drought. Statistical results show that the water vapor from southwest of Yunnan in April–June contributes more than that from the east at the seasonal scale. In April–June 2019, however, the southern branch trough(SBT) was abnormally weak, the large and strong anticyclonic wind anomaly prevailed over the Bay of the Bengal(BOB), and the meridional water vapor transport to Yunnan was weak. At the subseasonal scale, the weaker SBT lasted the longest, and the strong convection over the BOB came up late despite of an early onset of the SCSSM, which resulted in reduced low-level moisture convergence in Yunnan and development of drought prior to the SCSSM onset. From the onset of SCSSM to the start of rainy season in SWC, the SBT and meridional water vapor transport from the BOB were still weak, and the water vapor was mainly transported into the coastal area of South and Southeast China rather than Yunnan. After the start of the rainy season in SWC, the SBT was still weak. This led to less moisture transport in the westerlies to the west of Yunnan and the persistent extreme drought. Both the statistical results and case analysis indicate that the stronger Australian high in spring and early summer of 2019 was associated with the abnormally strong anticyclone over the BOB and the always weak SBT. In sum, the anomalous weakness of SBT played a critical role in the extreme drought occurrence and persistence in Yunnan of Southwest China in 2019.
