THERMAL FORCING IMPACTS OF THE EASTERLY VORTEX ON THE EAST-WEST SHIFT OF THE SUBTROPICAL ANTICYCLONE OVER WESTERN PACIFIC OCEAN

By employing the NCEP/NCAR reanalysis data sets(1 000 to 10 hPa,2.5°× 2.5°),the thermal forcing impacts are analyzed of an easterly vortex(shortened as EV) over the tropical upper troposphere on the quasi-horizontal movement of the Western Pacific Subtropical Anticyclone(shortened as WPS A) during 22-25 June 2003.The relevant mechanisms are discussed as well.It is shown that the distribution and intensity of the non-adiabatic effect near the EV result in the anomalous eastward retreat of the WPSA.The WPSA prefers extending to the colder region,i.e.,it moves toward the region in which the non-adiabatic heating is weakening or the cooling is strengthening.During the WPSA retreat,the apparent changes of non-adiabatic heating illustrate the characteristics of enhanced cooling in the east side of the EV.Meanwhile,the cooling in the west side exhibits a weakened eastward trend,most prominently at 300 hPa in the troposphere.The evidence on the factors causing the change in thermal condition is found:the most important contribution to the heating-rate trend is the vertical transport term,followed in turn by the local change in the heating rate term and the horizontal advection term.As a result,the atmospheric non-adiabatic heating generated by the vertical transport and local change discussed above is mainly connected to the retreat of the WPSA.     

热带对流层上空东风带扰动影响西太平洋副热带高压的个例分析

利用NCEP/NCAR1000—10hPa2.5°×2.5°日平均和每日4次再分析资料,分析了2003年6月19—25日热带对流层上空东风带扰动对西太平洋副热带高压东西向进退的影响。结果表明:热带对流层上空东风带扰动从对流层中低层伸展到50hPa高度附近,在200hPa上表现最为明显,在热力场上表现出“上暖强,下冷弱”的垂直分布特征。当西太平洋副热带高压南/北侧的东/西风带上的扰动在相向运动中抵达同一经度上时,对应于西太平洋副热带高压的异常东退。垂直涡度方程的诊断分析表明:在东风带扰动附近,涡度倾向效应贯穿于对流层整层到50hPa高度上,在200hPa高度附近表现最显著,当高层东风带扰动东/西侧的负/正变涡增强时,当东/西风带扰动在相向移动过程中,它们涡度倾向正值区在130°E南北打通时,西太平洋副热带高压出现突然东撤。涡度方程分析还表明,对于涡度倾向变化的贡献中,水平涡度平流的贡献最大、β效应的贡献最小;当东风带扰动附近的水平涡度平流和β效应增强时、且由β效应所引起的东/西风带扰动中的南、北风分量在130°E附近南北同相迭加出现“正压发展”时,有显著的正涡度增长,对应于西太平洋副热带高压的东撤。     

2006年黑龙江省4次区域性大(暴)雨过程对比分析

2006年夏季黑龙江省多次发生大范围强降雨过程,导致局地频发暴雨洪涝灾害,本文对2006年夏季的4次区域性大(暴)雨过程进行对比分析,综合运用了天气图、静止卫星云场和物理量诊断场,分析了区域性大(暴)雨产生的环流形势、基本物理量条件等,得出了对预报具有指导意义的特征。     

Case Study on the Impact of the Vortex in the Easterlies in the Tropical Upper Troposphere on the Western Pacific Subtropical Anticyclone

By employing the NCEP/NCAR reanalysis data （1000-10 hPa, 2.5°×2.5°）, the impact of the vortex in the easterlies （EV） over the tropical upper troposphere on the zonal movement of the western Pacific subtropical anticyclone （WPSA） during 19-25 June 2003 is analyzed in this paper. It is shown that the EV can extend from middle troposphere to the height of 50 hPa, reaching a maximum at 200 hPa. The vertical thermal distribution appears to be ＂warmer in the upper layer and colder in the lower layer＂. The WPSA retreats eastward abnormally when the EV and the vortex in the westerlies （WV） encounter around the same longitude while they move toward each other. It is also shown that the vorticity variation extends from the troposphere to the height of 50 hPa, with the most prominent change occurring at 200 hPa by the diagnostic analyses of the vertical vorticity equation. The WPSA appears to retreat abnormally eastward while the negative/positive vorticity change becomes stronger near the east/west side of the EV, and the areas with positive vorticity tendency both in the EV and WV join together into one belt along 130°E during the process of the EV and the WV moving toward each other. In the vorticity equation, the positive contribution caused by the horizontal advection term is the maximum, and the minimum is caused by theβ effect. It is also found that enhanced horizontal vorticity advection andβ effect, as well as the ＂barotropic development＂ resulted from the in-phase superposition of the southerly and the northerly winds in the easterlies and westerlies near 130~E, are in agreement with the WPSA eastward retreat.