Based on daily observation data in the Three Gorges Region(TGR)of the Yangtze River Basin and global reanalysis data,the authors analyzed the climate characteristics and associated temporal variations in the main mete...Based on daily observation data in the Three Gorges Region(TGR)of the Yangtze River Basin and global reanalysis data,the authors analyzed the climate characteristics and associated temporal variations in the main meteorological factors in 2021,as well as the year’s climatic events and meteorological disasters.The 2021 average temperature was 0.2℃above the 1991-2020 average and the 13 th-warmest year since 1961.Seasonally,winter and autumn were both warmer than usual.The annual mean precipitation was 12.8%above normal,and most regions experienced abundant rainfall throughout the year.The seasonal variation in precipitation was significant and the TGR had a wetter-than-normal spring and summer.The number of rainstorm days was higher than normal;the wind speed was above normal;and the relative humidity was higher than normal.In terms of rain acidity,2021 was tied with 2020 as the lowest since 1999.From mid-September to early October 2021,the TGR experienced exceptional high-temperature weather,which was driven by abnormal activity of mid-and high-latitude atmospheric circulation over the Eurasian continent and the western Pacific subtropical high(WPSH).In addition,a strong blocking high over the Ural Mountains accompanied by intense mid-latitude westerly winds prevented cyclonic disturbances from extending to the subtropical region.As a result,under the combined effect of the weaker-than-normal cold-air activities and the anomalous WPSH,the TGR experienced extreme high-temperature weather during early autumn 2021.展开更多
Using the Arctic Oscillation(AO) index,the exceptional winter(DJF) of 2009 has been analyzed.The middle-to-high latitudes of the Northern Hemisphere suffered from a nearly zonally symmetric anomaly of temperature and ...Using the Arctic Oscillation(AO) index,the exceptional winter(DJF) of 2009 has been analyzed.The middle-to-high latitudes of the Northern Hemisphere suffered from a nearly zonally symmetric anomaly of temperature and pressure.This situation revealed that two negative AO events occurred in the winter of 2009/2010,with unprecedented low values in January 2009 and February 2010.The negative AO event in January 2009 can be further divided into two stages:the first stage was mainly driven by enhanced upward-propagating planetary waves,which led to a weak stratospheric polar vortex associated with a downward-propagating negative AO signal;the second stage was caused by a lower tropospheric positive temperature anomaly in the high latitudes,which maintained the positive geopotential height anomaly of the first stage.The two successively occurring stages interacted and caused the lower troposphere to experience a strong and lengthy persistence of the negative AO event.We consider that the second event of negative AO in February 2010 is related to the downward-propagating negative AO after sudden stratospheric warming.Eleven long-persistence negative AO events were analyzed using reanalysis data.The results suggest that the negative AO in the troposphere might have been caused by stratospheric sudden warming,a downward-propagating weak stratospheric circulation anomaly or dynamic processes in the troposphere.Further study shows that the negative phase of the AO in the winter of 2009/2010 corresponded to a wide range of temperature and precipitation anomalies in the Northern Hemisphere.Therefore,to improve the accuracy of weather forecasting and climate prediction,more attention should be paid to the AO anomaly and its impact.展开更多
基金jointly supported by the funds of the Strategic Cooperation Agreement Project between the China Meteorological Administration and the Three Gorges Corporation[Grant No.0704182]the Comprehensive Monitoring Program for Operational Safety of the Three Gorges Project[Grant No.SK2021015]financed by the Ministry of Water Resources of China.
文摘Based on daily observation data in the Three Gorges Region(TGR)of the Yangtze River Basin and global reanalysis data,the authors analyzed the climate characteristics and associated temporal variations in the main meteorological factors in 2021,as well as the year’s climatic events and meteorological disasters.The 2021 average temperature was 0.2℃above the 1991-2020 average and the 13 th-warmest year since 1961.Seasonally,winter and autumn were both warmer than usual.The annual mean precipitation was 12.8%above normal,and most regions experienced abundant rainfall throughout the year.The seasonal variation in precipitation was significant and the TGR had a wetter-than-normal spring and summer.The number of rainstorm days was higher than normal;the wind speed was above normal;and the relative humidity was higher than normal.In terms of rain acidity,2021 was tied with 2020 as the lowest since 1999.From mid-September to early October 2021,the TGR experienced exceptional high-temperature weather,which was driven by abnormal activity of mid-and high-latitude atmospheric circulation over the Eurasian continent and the western Pacific subtropical high(WPSH).In addition,a strong blocking high over the Ural Mountains accompanied by intense mid-latitude westerly winds prevented cyclonic disturbances from extending to the subtropical region.As a result,under the combined effect of the weaker-than-normal cold-air activities and the anomalous WPSH,the TGR experienced extreme high-temperature weather during early autumn 2021.
文摘Using the Arctic Oscillation(AO) index,the exceptional winter(DJF) of 2009 has been analyzed.The middle-to-high latitudes of the Northern Hemisphere suffered from a nearly zonally symmetric anomaly of temperature and pressure.This situation revealed that two negative AO events occurred in the winter of 2009/2010,with unprecedented low values in January 2009 and February 2010.The negative AO event in January 2009 can be further divided into two stages:the first stage was mainly driven by enhanced upward-propagating planetary waves,which led to a weak stratospheric polar vortex associated with a downward-propagating negative AO signal;the second stage was caused by a lower tropospheric positive temperature anomaly in the high latitudes,which maintained the positive geopotential height anomaly of the first stage.The two successively occurring stages interacted and caused the lower troposphere to experience a strong and lengthy persistence of the negative AO event.We consider that the second event of negative AO in February 2010 is related to the downward-propagating negative AO after sudden stratospheric warming.Eleven long-persistence negative AO events were analyzed using reanalysis data.The results suggest that the negative AO in the troposphere might have been caused by stratospheric sudden warming,a downward-propagating weak stratospheric circulation anomaly or dynamic processes in the troposphere.Further study shows that the negative phase of the AO in the winter of 2009/2010 corresponded to a wide range of temperature and precipitation anomalies in the Northern Hemisphere.Therefore,to improve the accuracy of weather forecasting and climate prediction,more attention should be paid to the AO anomaly and its impact.
