Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5 ° N, 76.9 ° E) during ...Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5 ° N, 76.9 ° E) during the last week of June and the first week of September for the two contrasting summer monsoon years 1975 (a very strong monsoon year) and 1979 (a very weak monsoon year), a study has been made to examine the mean circulation features of the troposphere over India, and the structures of the temperatures and the winds of the middle atmosphere over Thumba. The study suggested that the axis of the monsoon trough (AMT) at 700 hPa shifted southward in 1975 and northward towards the foothills of the Himalayas in 1979, from its normal position. Superimposed on the low-pressure area (AMT) at 700 hPa, a well-defined divergence was noticed at 200 hPa over the northern India in 1975.The mean temperatures at 25,50 and 60 km (middle atmosphere) over Thumba were cooler in 1975 than in 1979. While a cooling trend in 1975 and warming trend in 1979 were observed at 25 and 50 km, a reversed picture was noticed at 60 km. There was a weak easterly / westerly (weak westerly phase) zonal wind in 1975 and a strong easterly zonal wind in 1979. A phase reversal of the zonal wind was observed at 50 km. A tentative physical mechanism was offered, in terms of upward propagation of the two equatorially trapped planetary waves i.e. the Kelvin and the mixed Rossby-gravity waves, to explain the occurrence of the two spells of strong warmings in the mesosphere in 1975.展开更多
In this study,the climatology and long-term trends of middle atmospheric temperatures at mid-latitudes are investigated using Rayleigh/Sodium lidar observations collected from January 2010 to December 2021 over Hefei,...In this study,the climatology and long-term trends of middle atmospheric temperatures at mid-latitudes are investigated using Rayleigh/Sodium lidar observations collected from January 2010 to December 2021 over Hefei,China(32°N,117°E).The seasonal variations and vertical profiles of lidar-derived temperatures demonstrate strong agreement with temperature measurements from the Microwave Limb Sounder(MLS)instrument on the Earth Observing System(EOS)Aura satellite.In terms of seasonal variation,middle atmospheric temperatures primarily exhibit annual oscillations(AO)and semi-annual oscillations(SAO).Harmonic analysis of the lidar and MLS temperature data reveals close phase alignment for both AO and SAO,with AO amplitudes ranging from 2 to 6 K,and SAO amplitudes from 1 to 4 K.The dependence of temperature on solar forcing was analyzed using the F10.7 index as a proxy,showing positive solar response coefficients at all altitudes,with a maximum of 15±1.1 K/100 SFU observed near 42–44 km.After removing the temperature response to solar cycle variations,a cooling trend in mid-latitude temperatures is evident across all altitudes,ranging from 3 to 6 K/decade.展开更多
全球变暖加剧了气候系统的不稳定性和极端天气的频发,“热岛效应”和高温热浪的叠加,给人们的生命安全和经济生产造成巨大损失,本文利用1971—2022年长江中游234个站点日降水量和最高气温数据、美国国家环境预报中心/国家大气研究中心(N...全球变暖加剧了气候系统的不稳定性和极端天气的频发,“热岛效应”和高温热浪的叠加,给人们的生命安全和经济生产造成巨大损失,本文利用1971—2022年长江中游234个站点日降水量和最高气温数据、美国国家环境预报中心/国家大气研究中心(National Centers for Environmental Predic⁃tion/National Center for Atmospheric Research,NCEP/NCAR)再分析资料和美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration,NOAA)海表温度(简称“海温”)资料,分析夏季高温异常年的大气环流特征及其与海温的关系。结果表明:近52 a来尤其是进入21世纪,长江中游夏季高温日呈显著增加趋势,年均高温日为19 d。其中,2022年高温日数最多达74 d,与近30 a气候态平均相比,距平百分率高出163%,1987年高温日最少仅5 d。夏季高温日偏多年,在副极地波导的遥相关波列影响下,东亚大陆高压增强,反气旋性环流控制长江中游地区,同时东亚夏季西风急流位置偏北,促使西太平洋副热带高压西伸北抬,强烈的下沉运动抑制低层对流发展,辐射增温作用明显。高温日数与赤道北印度洋、北大西洋和中低纬西太平洋海温,尤其是夏季海温呈正相关关系,与赤道中东太平洋海温呈负相关。从前冬开始赤道北印度洋和北大西洋海温持续偏高,中低纬西太平洋海温逐渐开始升高,同时夏季赤道中东太平洋呈异常La Niña状态,有利于长江中游夏季高温日异常偏多。展开更多
文摘Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5 ° N, 76.9 ° E) during the last week of June and the first week of September for the two contrasting summer monsoon years 1975 (a very strong monsoon year) and 1979 (a very weak monsoon year), a study has been made to examine the mean circulation features of the troposphere over India, and the structures of the temperatures and the winds of the middle atmosphere over Thumba. The study suggested that the axis of the monsoon trough (AMT) at 700 hPa shifted southward in 1975 and northward towards the foothills of the Himalayas in 1979, from its normal position. Superimposed on the low-pressure area (AMT) at 700 hPa, a well-defined divergence was noticed at 200 hPa over the northern India in 1975.The mean temperatures at 25,50 and 60 km (middle atmosphere) over Thumba were cooler in 1975 than in 1979. While a cooling trend in 1975 and warming trend in 1979 were observed at 25 and 50 km, a reversed picture was noticed at 60 km. There was a weak easterly / westerly (weak westerly phase) zonal wind in 1975 and a strong easterly zonal wind in 1979. A phase reversal of the zonal wind was observed at 50 km. A tentative physical mechanism was offered, in terms of upward propagation of the two equatorially trapped planetary waves i.e. the Kelvin and the mixed Rossby-gravity waves, to explain the occurrence of the two spells of strong warmings in the mesosphere in 1975.
基金supported by the National Natural Science Foundation of China(Grant 42125402,42174183 and 42304165)the National Key Technologies R&D Program of China(Grant 2022YFF0503703)+7 种基金the B-type Strategic Priority Program of CAS(Grant XDB0780000)the Chinese Meridian Projectthe Fundamental Research Funds for the Central Universitiesthe Joint Open Fund of Mengcheng National Geophysical Observatory(MENGO-202406,MENGO-202407)the National Natural Science Foundation of China(NSFC)Distinguished Overseas Young Talents ProgramBasic Research Project of the National Key Laboratory of Deep Space Exploration(NKLDSE2023A002)the Pre-research project on Civil Aerospace Technologies No.D010305 and D010301 funded by China National Space Administration(CNSA)Supported by the Specialized Research Fund for State Key Laboratory of Solar Activity and Space Weathe.
文摘In this study,the climatology and long-term trends of middle atmospheric temperatures at mid-latitudes are investigated using Rayleigh/Sodium lidar observations collected from January 2010 to December 2021 over Hefei,China(32°N,117°E).The seasonal variations and vertical profiles of lidar-derived temperatures demonstrate strong agreement with temperature measurements from the Microwave Limb Sounder(MLS)instrument on the Earth Observing System(EOS)Aura satellite.In terms of seasonal variation,middle atmospheric temperatures primarily exhibit annual oscillations(AO)and semi-annual oscillations(SAO).Harmonic analysis of the lidar and MLS temperature data reveals close phase alignment for both AO and SAO,with AO amplitudes ranging from 2 to 6 K,and SAO amplitudes from 1 to 4 K.The dependence of temperature on solar forcing was analyzed using the F10.7 index as a proxy,showing positive solar response coefficients at all altitudes,with a maximum of 15±1.1 K/100 SFU observed near 42–44 km.After removing the temperature response to solar cycle variations,a cooling trend in mid-latitude temperatures is evident across all altitudes,ranging from 3 to 6 K/decade.
文摘全球变暖加剧了气候系统的不稳定性和极端天气的频发,“热岛效应”和高温热浪的叠加,给人们的生命安全和经济生产造成巨大损失,本文利用1971—2022年长江中游234个站点日降水量和最高气温数据、美国国家环境预报中心/国家大气研究中心(National Centers for Environmental Predic⁃tion/National Center for Atmospheric Research,NCEP/NCAR)再分析资料和美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration,NOAA)海表温度(简称“海温”)资料,分析夏季高温异常年的大气环流特征及其与海温的关系。结果表明:近52 a来尤其是进入21世纪,长江中游夏季高温日呈显著增加趋势,年均高温日为19 d。其中,2022年高温日数最多达74 d,与近30 a气候态平均相比,距平百分率高出163%,1987年高温日最少仅5 d。夏季高温日偏多年,在副极地波导的遥相关波列影响下,东亚大陆高压增强,反气旋性环流控制长江中游地区,同时东亚夏季西风急流位置偏北,促使西太平洋副热带高压西伸北抬,强烈的下沉运动抑制低层对流发展,辐射增温作用明显。高温日数与赤道北印度洋、北大西洋和中低纬西太平洋海温,尤其是夏季海温呈正相关关系,与赤道中东太平洋海温呈负相关。从前冬开始赤道北印度洋和北大西洋海温持续偏高,中低纬西太平洋海温逐渐开始升高,同时夏季赤道中东太平洋呈异常La Niña状态,有利于长江中游夏季高温日异常偏多。
