The Characteristics of “OLR” for 1991 Mei–yu
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摘要: 该文利用美国NOAA卫星1991年(及1980和1985年)雨季候平均OLR资料及常规天气观测资料,对1991年江淮洪涝梅雨的OLR场特征进行分析。分析了1991梅雨期的OLR及其距平场以及季内变化(ISV)的经、纬向传播特征;揭示了ITCZ与副热带高压的变化与梅雨的关系以及青藏高原OLR的异常与梅雨的关系;指出西太平洋ITCZ的提前出现以及青藏高原冬季OLR的正距平(积雪少)是1991年洪涝梅雨提前发生的先兆。最后分析了1991年梅雨活跃期与中断期的OLR分布特征,并与印度季风雨相比较,发现两者开始日期Abstract: Using the mean pentad Outgoing Longwave Radiation (OLR) data observed from the NOAA satellites and the conventional weather observations for the 1991 Mei–yu season, the diagnostic study of the characteristics of the OLR is conducted. The paper describes the OLR and its anomalies pattern and the characteristics of propagation of the intraseasonal variation (ISV) of OLR during the 1991 flood Mei–yu periods. It is revealed that the variation of the ITCZ and the subtropical high are related to the evolution of the Mei–yu. The relationship between the anomalies of OLR over Tibet Plateau and the flood Mei–yu is also revealed. The results show that the earlier ITCZ occurrence in the western Pacific and the positive OLR anomalies (snow cover less than normal) over Tibet Plateau in winter are the important indications for the earlier onset date of the 1991 Mei–yu. Finally, by analyzing the features of the OLR pattern for the active and break phases of the 1991 Mei–yu and comparing with that of Indian monsoon, it is found that their onset dates are different from each other and their active phases either same or contrary. It is suggexted that the complication of the Mei–yu in China is mainly due to the interaction between the middle latitude cold air and two kinds (east Asia and south Asia) of monsoon events.
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Key words:
- OLR;
- ITCZ;
- Mei–yu;
- Monsoon;
- Tibet Plateau
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