春季青藏高原大气热源季节内振荡特征及其维持机制  

Intraseasonal Oscillation of Atmospheric Heat Source over the Qinghai-Xizang Plateau in Boreal Spring and Its Maintaining Mechanism

作　　者：刘伯奇[1] 段亚楠 李健颖 毛江玉[2] LIU Boqi;DUAN Yanan;LI Jianying;MAO Jiangyu(Institute of Climate System,Chinese Academy of Meteorological Sciences,Beijing 100081,China;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国气象科学研究院气候与气候变化研究所,北京100081 [2]中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG),北京100029

出　　处：《高原气象》2021年第6期1419-1431,共13页Plateau Meteorology

基　　金：科技部科技基础资源调查专项(2019QZKK0105);中国科学院战略性先导科技专项(XDB40000000);国家自然科学基金项目(41775052,41830969,41730963)。

摘　　要：青藏高原大气热源在春季的形成,标志着高原对区域和全球天气气候热力强迫的开始。本文基于1981-2010年台站观测和JRA-55大气环流再分析资料,研究了春季青藏高原大气热源季节内尺度的时空变化特征。发现高原大气热源在春季存在显著的10~20天准双周振荡,在空间分布上表现为纬向偶极子型与单极子型异常模态之间的交替出现。其中,偶极子模态表现为凝结潜热异常在高原西北部和东南部的反相变化,而单极子模态则表现为高原上空感热异常一致性变化。在单极子模态的位相下,高原感热异常势必诱发低层环流异常,改变了高原东、西部的水汽输送,从而引起局地降水和凝结潜热异常,产生偶极子型的大气热源分布;随后,这种偶极子型大气热源异常又导致近地面纬向风调整,令高原整体感热异常不断加强,造成水汽输送再次改变,凝结潜热加热随之逐渐减弱,由此高原大气热源恢复单极子模态。因此,春季高原上空感热、凝结潜热和局地环流的相互作用是维持高原大气热源准双周振荡的关键机制。The formation of atmospheric heat source over the Qinghai-Xizang Plateau(QXP)in boreal spring indicates the beginning of the QXP thermal forcing on regional and global weather and climate. Based on the JRA-55 atmospheric reanalysis and station-based observation data from 1981 to 2010,the present study investigated the spatial and intraseasonal variations of the spring atmospheric heat source over the QXP. A significant 10-20-day intraseasonal oscillation(ISO)was found in the atmospheric heat source over the QXP in boreal spring. It featured an alternation between zonal dipole and monopole mode of the spring atmospheric heat source over the QXP. The dipole mode was characterized by the inverse change of anomalous condensation latent heat between the northwestern and southeastern QXP. While the monopole mode exhibited a predominantly positive or negative sensible heat anomalies over the QXP. In the phases with the dominant monopole mode,the anomalous sensible heat over the QXP could produce the low-level circulation anomaly. It gave rise to the distinct water vapor transport between the eastern and western QXP,inducing the opposite variation of the local precipitation and condensation latent heat anomaly over the eastern and western QXP. The ISO thus entered its zonal dipole mode.As the atmospheric response to the anomalous condensation latent heat in the zonal dipole mode,the near-surface zonal wind was changed to facilitate the sensible heat anomaly over the QXP. In turn,the water vapor transport was altered over the eastern and western QXP but reversed its original property. As a result,the condensation latent heat anomaly decreased gradually over the QXP. On the one hand,the zonal dipole mode started to weaken. On the other hand,the response of the near-surface wind to the zonally asymmetric condensation heat anomaly could enhance the anomalous sensible heat over the QXP. Therefore,the atmospheric heat source over the QXP returned to the monopole mode with the homogeneous sensible heat anomaly. Finally,the inte

关 键 词：青藏高原 大气热源 准双周振荡 感热 凝结潜热 

分 类 号：P466[天文地球—大气科学及气象学]