一次暴雨过程中重力波和湿位涡分析

Analysis on Gravity Waves and Moist Potential Vorticity During a Rainstorm Process

利用NCEP逐日再分析资料和常规的地面观测资料,对四川中东部2009年7月31日的局地暴雨过程的湿位涡场及重力波进行了诊断与分析。由于绝热、无摩擦大气中湿位涡守恒,可以得出湿位涡的分布及时空变化与暴雨的发生发展有密切的关系。散度场分布和非线性平衡方程的诊断结果表明,暴雨过程中重力波特征有非常明显的变化。大气的不稳定性不仅是暴雨的激发源,伴随的还有重力波的产生发展,因此湿位涡和重力波都对暴雨预报有很好的效果。

Based on the NCEP daily reanalysis data and the conventional surface observations in the middle and eastern part of Sichuan Province, an analysis of gravity waves and wet vorticity during the rainstorm on July 31,2009 was carried out.As the motion in the atmosphere without diabatic heating and frictional dissipation conserves moist potential vorticity,it is showed that the moist potential vorticity distribution and temporal change was closely related to the development of the heavy rainfall.The divergence fields and diagnostic results of the non-linear balance equation showed that the gravity wave characteristics had a very significant change during heavy rainfall.The atmospheric instability not only is the excitation source of heavy rain ,but also generates gravity waves, so moist potential vorticity and gravity waves play a good role in the forecast of the heavy rainfall.