夏季青藏高原加热和环流场的日变化

通过使用NCEP/NCAR再分析资料，分析了夏季青藏高原地区非绝热加热场的日变化特征以及高原上空环流场的日变化特点。分析发现青藏高原及其邻近地区上空环流的日变化在欧亚地区大气环流系统中表现最为显著。环流日变化是被非绝热加热的日变化所驱动的，特别是被太阳辐射日变化所驱动。由于高原上空大气柱质量远小于低海拔的平原地区，故太阳辐射日变化引起的加热日变化可在高原地区产生更为显著的环流日变化。通过位涡方程的诊断证实，白天高原加热增强，可在大气上层制造大量负位涡并向周边地区辐散，使高原地区大气高层成为负涡源。而低层则是加热制造正位涡，并使周边地区向高原的辐合增强，摩擦耗散是低层抑制正位涡增长的主要因素。而夜间加热减弱使高原对局地环流的影响作用大为减弱。故而高原及其周边地区的局地环流也具有明显的日变化特征。

The Diurnal Variation of the Atmospheric Circulation and Diabatic Heating over the Tibetan Plateau

The NCEP/NCAR reanalysis data are employed to analyze the diurnal variation of the diabatie heating and atmospheric circulation over the Tibetan Plateau and itg surrounding areas. The atmosphere over the TP is most sensitive to the diurnal change of heating, and it results in the vivid diurnal change feature over the TP and its surrounding areas. Its diurnal change is consistent with that of the heating fieldg, especially with diurnal change of the solar heating. Because the mass of the atmospheric column over the TP is much lighter than other regions, the diurnal change of solar radiation heating causes more significant circulation variation over the TP. The equation of the potential vorticity is employed to diagnose the dynamics of diurnal circulation variation in the paper. The result shows while the solar radiation gradually enhanced in the daytime, the positive vorticity of lower level atmosphere and negative vorticity of high level atmosphere over the TP is increase. All these lead to the most significant circulation and weather diurnal changes over the TP and its surrounding areas. The features of the diurnal change of the atmospheric circulation are in accordance with both theory and data analysis results in their phase and circulation patterns.