高原及冷空气对1998和1991年夏季西太副高及雨带的影响

Impact of Plateau and Cold Air on SHWP and Rain Belt Summer in 1998 and 1991

为了寻找西太副高南北急剧摆动的中、短期预报着眼点 ,本文利用 1998和 1991年 6～ 8月的逐日天气图资料、第二次青藏高原气象科学试验的实测资料 ,以及NCEP/NCAR的 2 .5°× 2 .5°经 /纬度格点的日平均u、v及高度再分析资料等 ,分析了高原涡东移、南亚高压南北摆动 ,以及北方冷空气入侵等对西太副高脊线及其相伴雨带摆动的影响。主要结论如下 :1)凡高原东部气柱平均厚度ΔH3 0 050 0 ≥392gpdm时 ,未来高原涡将东移出高原 ,激发西南涡产生东移 ,使西太副高南落 ,长江中、下游流域产生暴雨 ;2 )南亚高压东段脊线和西太副高西段脊线的南北摆动趋势相同 ,但前者更稳定 ,且常提前 3天 ,可据此预报西太副高的摆动及其相伴雨带的位置 ;3)若北方有冷空气持续南下 ,华北与华南、江南分别出现 2m·s-1以上的南风负、正距平 ,将易在该南风正、负距平过渡区且偏于负距平区一侧产生暴雨 ,并使西太副高稳定少动。

The 500 hPa Subtropical High over the West Pacific (SHWP) is one of the members of summery monsoon systems in Eastern Asia, it has the important influence on the main rain belt in China summer. In this paper to seek the forecast precursors for medium\| and short\|range forecast of the SHWP moving southward and northward suddenly, the impacts on the SHWP moving southward and northward and associated rain belt of the Qinghai\|Xizang Plateau (QXP) vortexes moving eastward, the 100 hPa Southern Asia High (SAH) moving southward and northward, as well as the cold air invading from the North have been analyzed, utilizing the daily weather maps from June to August in 1998 and 1991, and the observational data from the Second Meteorology Science Test on the QXP, and the daily averaged gridded reanalysis data (e.g. \%u, v, h\%) on 2.5°×2.5° from NCEP/NCAR. The main conclusions are as follows: 1) If the air\|column thickness between 300 and 500 layers over the eastern QXP is greater than or equal to 392 gpdm, then the QXP vortexes moves eastward out of the QXP, and the southwest vortexes occurs and moves eastward, as a result, the SHWP moves southward and the rainstorm belt occurs in mid\| and lower reaches of Changjiang River in the future. 2) Both the eastern section of SAH ridge line and the west section of the SHWP ridge line have the same trend of moving southward and northward. But the former is much more stable and changes three days ahead. We can predict the moving of SWHP and the associated rain belt. 3) If there are the cold air invading in North China and more than 2 m·s\+\{-1\} positive and negative south wind anomaly on 850 hPa occurring Changjiang River, the rainstorm belt occurs easily in the transition band of the positive and negative anomaly of the south wind, especially on the negative anomaly side. It makes the SWHP more stable. 4) Certainly, the combined consideration will be needed in real forecast, and the first priority will be given to the SAH moving and the north cold air invading.