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近16年暖季青藏高原东部两类中尺度对流系统(MCS)的统计特征
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国家重点研发计划项目2018YFC0809400,国家自然科学基金项目91637211、41775046、41675045,中国科学院青年创新促进会项目


Statistical Features of Two Types of Mesoscale Convective Systems (MCSs) Generated over the Eastern Tibetan Plateau during 16 Consecutive Warm Seasons
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    摘要:

    利用日本高知大学提供的逐小时分辨率静止卫星云顶黑体亮温(TBB)资料,使用模式匹配算法对2000~2016年(2005年除外)暖季(5~9月)青藏高原东部的两类中尺度对流系统(MCS)进行了识别和追踪,并利用人工验证订正了结果。基于此,利用NOAA的CMORPH(Climate Prediction Center Morphing)降水资料和NCEP的CFSR(Climate Forecast System Reanalysis)再分析资料对高原东部两类MCS进行了统计和对比研究。研究发现,7月和8月是高原东部MCS生成最活跃的季节,然而,此两个月能够东移出高原MCS的比例最小;5月虽然MCS生成数最少,但是移出率高达近40%。对比表明,能够东移出高原的MCS(V-MCS)比不能移出的MCS(N-MCS)生命史更长,触发更早,短生命史个例占比更低。暖季各个月份,相比于N-MCS,V-MCS的对流更旺盛且发展更快,然而,由于其发生频数远低于N-MCS,总体而言,V-MCS对高原东部的降水贡献率仅为15%左右,是N-MCS相应数值的一半左右。高原东部两类MCS的环流特征差异显著,有利于V-MCS发生、维持和东移的因子主要位于对流层中低层(西风带短波槽、西风引导气流、低层风场切变),而在对流层高层,N-MCS拥有更好的高空辐散条件(其对应的南亚高压更强)。

    Abstract:

    Two types of mesoscale convective systems (MCSs) generated over the eastern Tibetan Plateau (TP) during 16 consecutive warm seasons were identified and tracked by an automatic tracking algorithm based on hourly geostationary satellite TBB data that were provided by Kochi University. Following the manual verification of the automatic tracking results, statistical and comparative analyses of these two types of MCSs were conducted using NOAA’s CMORPH (Climate Prediction Center Morphing) precipitation data and NCEP’s CFSR (Climate Forecast System Reanalysis) reanalysis data. The main results show that July and August were the most active months regarding the MCSs’ generation over the eastern section of the plateau, but the percentages of MCSs’ vacating the TP of these two months were the lowest. In May, the number of MCSs generated reached a minimum, but up to nearly 40% of the MCSs could vacate the TP. The MCSs that could vacate the TP (V-MCS) usually showed a longer lifespan, earlier triggering time, and lower proportion of short lifespan cases, compared with the MCSs that could not vacate the TP (N-MCS). During the period of the research, the V-MCSs were usually faster in development and stronger in intensity, compared with the N-MCSs. However, owing to the much lower frequency in the occurrence of V-MCSs, their contribution to the local precipitation was only about 15%, which was approximately half the contribution of the N-MCSs. The composite circulation features of the V-MCSs and N-MCSs that were generated over the eastern plateau were significantly different. The shortwave trough and stronger westerly wind in the middle troposphere and the cyclonic wind shear in the lower troposphere provided more favorable conditions for the V-MCSs’ occurrence, maintenance, and eastward displacement. In contrast, divergence conditions in the upper troposphere were more conducive to the N-MCSs (the associated South Asia high in this type was stronger).

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麦子,傅慎明,孙建华.2020.近16年暖季青藏高原东部两类中尺度对流系统(MCS)的统计特征[J].气候与环境研究,25(4):385-398. MAI Zi, FU Shenming, SUN Jianhua.2020.Statistical Features of Two Types of Mesoscale Convective Systems (MCSs) Generated over the Eastern Tibetan Plateau during 16 Consecutive Warm Seasons[J].Climatic and Environmental Research (in Chinese],25(4):385-398.

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  • 收稿日期:2019-03-22
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  • 在线发布日期: 2020-07-28
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