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方宗义, 覃丹宇, 黄勇, 李博. 梅雨锋云系的模态研究Ⅱ:出现频率及转换特点[J]. 大气科学, 2014, 38(4): 719-726. DOI: 10.3878/j.issn.1006-9895.2013.13099
引用本文: 方宗义, 覃丹宇, 黄勇, 李博. 梅雨锋云系的模态研究Ⅱ:出现频率及转换特点[J]. 大气科学, 2014, 38(4): 719-726. DOI: 10.3878/j.issn.1006-9895.2013.13099
FANG Zongyi, QIN Danyu, HUANG Yong, LI Bo. Modes of Meiyu Frontal Cloud Systems. Part Ⅱ:Frequencies and Transitional Characteristics[J]. Chinese Journal of Atmospheric Sciences, 2014, 38(4): 719-726. DOI: 10.3878/j.issn.1006-9895.2013.13099
Citation: FANG Zongyi, QIN Danyu, HUANG Yong, LI Bo. Modes of Meiyu Frontal Cloud Systems. Part Ⅱ:Frequencies and Transitional Characteristics[J]. Chinese Journal of Atmospheric Sciences, 2014, 38(4): 719-726. DOI: 10.3878/j.issn.1006-9895.2013.13099

梅雨锋云系的模态研究Ⅱ:出现频率及转换特点

Modes of Meiyu Frontal Cloud Systems. Part Ⅱ:Frequencies and Transitional Characteristics

  • 摘要: 基于经验正交函数(EOF)分解方法提取的1998~2008年梅雨活跃期共16次过程的梅雨锋云系主导模态,讨论了这些主导模态的发生频率、维持时间及相互转换特征。结果表明,在16个梅雨活跃期内,云系的第1主导模态正相位出现的频率最高,并且在4个活跃期内作为首次出现模态率先出现;第5模态正位相的出现频率最低,且该模态多数伴随其他模态一同出现,为过渡模态。统计发现,各主导模态的维持时间并不相同,其中第2模态负位相持续时间最长,为81 h;第5模态正位相的最大持续时间最短,仅为18 h;第6模态负位相的平均持续时间最长。对不同主导模态转换方向和频次的计算表明,各个位相的模态最多(最少)向9种(3种)(含正负位相)其他模态进行转换。除第6模态负位相和第5模态负位相向其他模态的转化具有较好的方向性外,其他模态间的相互转换多表现出随机性特征。其中,第6模态负位相在超过半数的情况下向第5模态负位相转换,而第5模态负位相则多向第3模态正位相和第1模态负位相进行转换。

     

    Abstract: On the basis of the leading modes of the Meiyu frontal cloud system extracted by the empirical orthogonal function (EOF) from the black body temperatures (TBBs) in the active periods of Meiyu during 1998 to 2008, the frequency of occurrence, persistence time, and transitional characteristics are investigated. There are seven independent leading modes for TBB anomalies (EOF1 to EOF7). The statistics show that the positive phase of EOF1 has the highest frequency of occurrence and can explain the first appearance mode in 25% of the total Meiyu processes. The positive phase of EOF5 has the lowest frequency of occurrence of all of these leading modes and is often mixed with other modes as a transition mode. In addition, the longest persistence time of the negative EOF2 is 81 h and is longer than that of the other leading modes, whereas the longest duration time of the positive EOF5 is only 18 h, which is shorter than that of the other leading modes. The negative phase of EOF6 has the longest mean duration time. The conversions between the leading modes are random, whereas only the negative EOF5 and EOF6 show better directionality. Among them, the probability for the transition from the negative phase of EOF6 to the negative phase of EOF5 is 66.67%, whereas the negative phase of EOF5 often transites to the positive phase of EOF3 and the negative phase of EOF1.

     

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