在气候变暖背景下,2022年夏季我国出现1961年以来平均气温最高和降水量次少的气候异常,并伴有最强的全国性(东北地区除外)高温过程和长江中下游及川渝地区大范围强伏旱。针对这次高温干旱的持续性和极端性,本文基于2022年6—8月全国216...在气候变暖背景下,2022年夏季我国出现1961年以来平均气温最高和降水量次少的气候异常,并伴有最强的全国性(东北地区除外)高温过程和长江中下游及川渝地区大范围强伏旱。针对这次高温干旱的持续性和极端性,本文基于2022年6—8月全国2162个气象站逐日最高气温和降水量以及NCEP(National Centers for Environmental Prediction)/NCAR(National Center for Atmospheric Research)逐日再分析资料等,分析其时空分布特征及环流形势,将对今后我国南方地区夏季高温干旱不同时间尺度的预报预测有一定参考价值。结果表明:2022年夏季,全国76.0%的站共出现48 198次高温,其中36.6%的站累计出现3001次极端高温事件,20次以上极端高温事件的站点均分布在四川盆地,高温状况远超21世纪以来的典型高温年份。全国性的高温过程从6月13日持续到8月30日,共计79 d,高温最强时段在8月11—24日。按照高温发生站次、持续时间、影响范围、强度等由强到弱综合排序,依次是华东、西南、华中、西北、华北和华南地区,其中西南地区极端性最强,而东北地区未出现高温。干旱时空分布特征与高温基本相似,全国最强干旱时段在8月中旬。2022年夏季,500 hPa欧亚中高纬度呈“两脊一槽”型,尤其在7—8月乌拉尔山和鄂霍次克海附近高压脊形成阶段性阻塞高压,强盛的副热带系统将两高之间活跃的冷空气大部分时段阻挡在50°N以北,造成我国“北涝南旱”的格局;低纬度的伊朗高压异常东伸,西太平洋副热带高压略偏北且异常西伸,两高压长时间贯通形成的高压带控制区气流辐散下沉,并持续阻碍水汽向中纬度输送,不利于长江流域产生降水。同时,对流层高层南亚高压异常偏东,与中层的西太平洋副热带高压相向而行,于8月中下旬在80°E—120°E范围内叠加,致使控制我国大范围的高压系统呈稳定正压结构,中心位于川渝上�展开更多
By use of the NCEP/ NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) is analyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric temperatures, the ...By use of the NCEP/ NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) is analyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric temperatures, the visible heat sources, and the diabatic heating rates in the whole atmospheric column on the seasonal variation of the SAH are discussed. Results show that the SAH has two seasonal balancing modes, one of which is the land high in summer and the other the ocean high in winter. The land high itself can be divided into two patterns as well, that is the Tibetan high and the Iranian high. Heating fields have important impacts on the seasonal variation of the SAH. The SAH is a warm high and its center has the property of heat preference, usually locating over or moving to an area with relatively larger heating rates. The annual cycle of the SAH is mainly controlled by the seasonal process of the latent and sensible heating in South Asia. Strong shortwave radiative heating in the north at high latitudes and over the Tibetan Plateau also has an effects on the northward movement and maintenance of the SAH. The cooling effect of infrared radiation is an important cause in weakening the SAH.展开更多
The tropical Indian Ocean （TIO） is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High （SAH） in summer. When the TIO i...The tropical Indian Ocean （TIO） is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High （SAH） in summer. When the TIO is warmer, the SAH strengthens and its center shifts southward. It is found that the variations in the SAH cannot be accounted for by the precipitation anomaly. A possible mechanism is proposed to explain the connection between the TIO and SAH： warmer SST in the TIO changes the equivalent potential temperature （EPT） in the atmospheric boundary layer （ABL）, alters the temperature profile of the moist atmosphere, warms the troposphere, which produces significant positive height anomaly over South Asia and modifies the SAH. An atmospheric general circulation model, ECHAM5, which has a reasonable prediction skill in the TIO and South Asia, was selected to test the effects of TIO SST on the SAH. The experiment with idealized heating over the TIO reproduced the response of the SAH to TIO warming. The results suggest that the TIO-induced EPT change in the ABL can account for the variations in the SAH.展开更多
文摘在气候变暖背景下,2022年夏季我国出现1961年以来平均气温最高和降水量次少的气候异常,并伴有最强的全国性(东北地区除外)高温过程和长江中下游及川渝地区大范围强伏旱。针对这次高温干旱的持续性和极端性,本文基于2022年6—8月全国2162个气象站逐日最高气温和降水量以及NCEP(National Centers for Environmental Prediction)/NCAR(National Center for Atmospheric Research)逐日再分析资料等,分析其时空分布特征及环流形势,将对今后我国南方地区夏季高温干旱不同时间尺度的预报预测有一定参考价值。结果表明:2022年夏季,全国76.0%的站共出现48 198次高温,其中36.6%的站累计出现3001次极端高温事件,20次以上极端高温事件的站点均分布在四川盆地,高温状况远超21世纪以来的典型高温年份。全国性的高温过程从6月13日持续到8月30日,共计79 d,高温最强时段在8月11—24日。按照高温发生站次、持续时间、影响范围、强度等由强到弱综合排序,依次是华东、西南、华中、西北、华北和华南地区,其中西南地区极端性最强,而东北地区未出现高温。干旱时空分布特征与高温基本相似,全国最强干旱时段在8月中旬。2022年夏季,500 hPa欧亚中高纬度呈“两脊一槽”型,尤其在7—8月乌拉尔山和鄂霍次克海附近高压脊形成阶段性阻塞高压,强盛的副热带系统将两高之间活跃的冷空气大部分时段阻挡在50°N以北,造成我国“北涝南旱”的格局;低纬度的伊朗高压异常东伸,西太平洋副热带高压略偏北且异常西伸,两高压长时间贯通形成的高压带控制区气流辐散下沉,并持续阻碍水汽向中纬度输送,不利于长江流域产生降水。同时,对流层高层南亚高压异常偏东,与中层的西太平洋副热带高压相向而行,于8月中下旬在80°E—120°E范围内叠加,致使控制我国大范围的高压系统呈稳定正压结构,中心位于川渝上�
基金This research was jointly sponsored by "The National Key Programme for Developing Basic Sciences"project (1998040900)Part Ⅰ, and the National Natural Science Foundation of China Project:"Studies on Interaction between the South Asia High and the Asian Monsoon and lts Mechanisms"under Grant No.40175021.
文摘By use of the NCEP/ NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) is analyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric temperatures, the visible heat sources, and the diabatic heating rates in the whole atmospheric column on the seasonal variation of the SAH are discussed. Results show that the SAH has two seasonal balancing modes, one of which is the land high in summer and the other the ocean high in winter. The land high itself can be divided into two patterns as well, that is the Tibetan high and the Iranian high. Heating fields have important impacts on the seasonal variation of the SAH. The SAH is a warm high and its center has the property of heat preference, usually locating over or moving to an area with relatively larger heating rates. The annual cycle of the SAH is mainly controlled by the seasonal process of the latent and sensible heating in South Asia. Strong shortwave radiative heating in the north at high latitudes and over the Tibetan Plateau also has an effects on the northward movement and maintenance of the SAH. The cooling effect of infrared radiation is an important cause in weakening the SAH.
基金supported by the National Key Technology R&D Program 2008BAK50B02CAS Innovation Key Program (Grant No. KZCX2-YW-BR-14)+2 种基金National Basic Research Program of China(2011CB309704)Special Scientific Research Project for Public Interest (Grant No. GYHY201006021)the National Natural Science Foundation of China (Grant Nos.40890155, 40775051, U0733002)
文摘The tropical Indian Ocean （TIO） is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High （SAH） in summer. When the TIO is warmer, the SAH strengthens and its center shifts southward. It is found that the variations in the SAH cannot be accounted for by the precipitation anomaly. A possible mechanism is proposed to explain the connection between the TIO and SAH： warmer SST in the TIO changes the equivalent potential temperature （EPT） in the atmospheric boundary layer （ABL）, alters the temperature profile of the moist atmosphere, warms the troposphere, which produces significant positive height anomaly over South Asia and modifies the SAH. An atmospheric general circulation model, ECHAM5, which has a reasonable prediction skill in the TIO and South Asia, was selected to test the effects of TIO SST on the SAH. The experiment with idealized heating over the TIO reproduced the response of the SAH to TIO warming. The results suggest that the TIO-induced EPT change in the ABL can account for the variations in the SAH.
