利用欧洲中心再分析资料(ERA-40)中1958-2001年气象场资料(世界时00时),分析了降水异常年850hPa湿位涡及其分量差异的原因。结果表明,降水异常年湿位涡和湿位涡正压部分的差异主要是由水汽的垂直分布差异引起稳定度的变化所致,而相对湿位涡和湿位涡斜压部分的差异,分别主要是由垂直涡度及纬向风的垂直切变和暖湿气流的经向切变所致。另外,还利用湿位涡的正压部分和斜压部分讨论了江淮夏季850hPa大气性质的变化,结果表明,近50年来,大气对流不稳定减弱,而斜压不稳定增强。
Based on the ERA-40 reanalysis data at GMT 00:00 during 1958-2001, the difference of moist potential vorticity (MPV) and its components in more and less years of protecipitation are analyzed. The results show that: (1) both MPV and MPV1 are affected by the variation of convective stability, which is mainly induced by the discrepancy of the moisture vertical gradient (2) relative MPVand MPV2 are mostly caused by the vertical vorticity and vertical shear of zonal wind as well as the meridional shear of warm and moist airflow, respectively. Additionally, MPV1 and MPV2 are used to investigate the atmospheric property of 850 hPa over Yangtze-Huaihe River basins. The result indicates that the atmospheric convective (baroclinic) instability weakens (strengthens) in recent 50 years.