Climatological distribution and diurnal variation

Authors: YongGuang Zheng Jiong Chen PeiJun Zhu

Publish Date: 2008/06/15

Volume: 53, Issue: 10, Pages: 1574-1586

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Abstract

The climatological distribution of mesoscale convective systems MCSs over China and its vicinity during summer is statistically analyzed based on the 10year 1996–2006 2004 excluded June–August infrared TBB Temperature of black body dataset Comparing the results obtained in this paper with the distribution of thunderstorms from surface meteorological stations over China and the distribution of lightning from loworbit satellites over China and its vicinity in the previous studies we find that the statistic characteristics of TBB less than −52°C can better represent the spatiotemporal distribution of MCSs over China and its vicinity during summer The spreading pattern of the MCSs over this region shows three transmeridional bands of active MCSs with obvious fluctuation of active MCSs in the band near 30°N It can be explained by the atmospheric circulation that the three bands of active MCSs are associated with each other by the summer monsoon over East Asia We focus on the diurnal variations of MCSs over different underlying surfaces and the result shows that there are two types of MCSs over China and its vicinity during summer One type of MCSs has only one active period all day long singlepeak MCSs and the other has multiple active periods multipeak MCSs Singlepeak MCSs occur more often over plateaus or mountains and multipeak MCSs are more common over plains or basins Depending on lifetimes and active periods singlepeak MCSs can be classified as Tibetan Plateau MCSs general mountain MCSs Ryukyu MCSs and so on The diurnal variation of multipeak MCSs is very similar to that of MCCs mesoscale convective complexes and it reveals that multipeak MCSs has longer life cycle and larger horizontal scale becomes weaker after sunset and develops again after midnight Tibetan Plateau MCSs and general mountain MCSs both usually develop in the afternoon but Tibetan Plateau MCSs have longer life cycle and more active MαCSs Ryukyu MCSs generally develop after midnight last longer time and also have more active MαCS The abundant moisture and favorable largescale environment over Indian monsoon surge areas lead to active MCSs and MαCSs almost at any hour all day during summer Due to local mountainvalley breeze circulation over the Sichuan Basin MCSs are developed remarkably more often during the nighttime and again there are also more active MαCSs Because of local prominent sealand breeze circulation over Guangxi and Guangdong the MCSs over this region propagate from sea to land in the afternoon and from land to sea after midnight The statistic characteristics of TBB less than −52°C clearly display the different climatological characteristics of MCSs owing to the thermal difference among water land and rough terrain Not only the largescale atmospheric circulation but also the local atmospheric circulation caused by the thermal difference among water land and rough terrain to a great extent determines the climatological distribution of MCSs over China and its vicinity during summer

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