利用青藏高原地区代表站点的实测地表热通量数据、JRA-55和NCEP再分析资料以及中国西北地区东部代表站点的降水资料等数据,通过波文比分析、奇异值分析(下称SVD)以及环流场的合成分析等方法,研究了青藏高原地区春季地表加热场异常与同期中国西北地区东部降水变率的关系,结果表明:(1)高原春季波文比值的变化反映出高原地表的非绝热加热中,春季感热加热的贡献较为显著,是高原春季地表加热的主要成分;(2)SVD分析表明,春季高原地表感热的异常与同期中国西北地区东部的降水存在负相关关系,春季高原地表感热增强的年份,中国西北地区东部的春季降水减少;(3)春季地表感热强-弱年的高原周边垂直环流偏差场表明,春季高原地表感热的年际异常增强(减弱)会引起高原周边地区的垂直环流场上升气流的减弱(增强);(4)相对涡度场、位势高度场、风场和水汽通量散度场的合成分析表明,春季高原地表感热偏强的年份,中国西北地区东部对流层高层以正涡度和气流的辐合运动异常为主,中低层以负涡度和辐散下沉运动异常为主,因此中国西北地区东部春季的水汽辐合由低层向高层逐渐减弱,不利于春季降水的发生。
To study the relationship between spring surface heat abnormal field over the Qinghai-Xizang Plateau and the precipitation in eastern part of Northwest China,in-situ surface heat flux data on four representative sites to analysis the change characteristics of atmospheric boundary layer of the Qinghai-Xizang Plateau,then the relationship between spring surface sensible heat over the Qinghai-Xizang Plateau and spring rainfall in the eastern part of Northwest China at interannual time scale was studied by using JRA-55 and NCEP reanalysis data and site observation of rainfall in the eastern part of Northwest China,research results indicate that:(1)The sensible heat flux contributes more than the latent heat flux and is the main part of the surface diabatic heating field over the Qinghai-Xizang Plateau in spring.(2)There is a negative correlation between the rainfall anomalies of the eastern part of Northwest China and the surface sensible heat anomalies over the Qinghai-Xizang Plateau;(3)Stronger surface sensible heating over the Qinghai-Xizang Plateau in spring leads to weaker upward movement of the vertical circulation over the Qinghai-Xizang Plateau and its surrounding areas in the same season and vice versa;(4)Composite analysis of relative vorticity,geopotential height,wind and water vapor flux divergence in the eastern part of Northwest China shows that when the inter-annual anomalies of spring surface sensible heating on the Qinghai-Xizang Plateau is positive,there is positive anomaly of vorticity in the upper troposphere and negative vorticity in the middle and lower troposphere in the studied areas,airflows exit convergence movement on the higher level and sinking motion on the lower levels,weakening the moisture convergence from lower to higher level,resulting in the decrease of spring rainfall in the eastern part of Northwest China.