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An analysis of the spatial pattern of summer persistent moderate-to-heavy rainfall regime in Guizhou Province of Southwest China and the control factors |
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| Authors: | Zhi-Yong Yin Yunlong Cai Xinyi Zhao Xiaoling Chen |
| Institution: | 1. Marine Science & Environmental Studies, University of San Diego, 5998 Alcala Park, San Diego, CA, 92110, USA 2. SKLLQG, Institute of Earth Environment, Chinese Academy of Science, Xi’an, 710075, People’s Republic of China 3. Department of Resources, Environment and Geography, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, People’s Republic of China 4. LIESMARS, Wuhan University, Wuhan, 430079, People’s Republic of China |
| Abstract: | In this study, we investigated spatial and temporal variation patterns of persistent moderate-to-heavy rainfall events in Guizhou Province of southwest China during 1951–2004. We first performed conventional frequency analysis using the annual maximum daily series at 36 weather stations fit to log-normal distribution curves. Then, we examined the frequencies of moderate-to-heavy rainfall events (>?=?20 mm/day) and persistent rainfall events (10–day running sum >?=?100 mm) during the summer season (June through August). Using principal component analysis, we identified various spatial patterns of the rainfall regime and macroscale atmospheric conditions that influence these patterns. It was found that a minor mode of variation in the 500 hPa geopotential height anomaly field over East Asia (the third principal component) had a very good relationship to the dominant regional precipitation regime (Spearman’s correlation coefficient?=?–0.623). This mode of circulation represents the N–S variation of the upper-air pressure gradients over East Asia. During its positive phase, the pressure gradient south of 40°N is reduced and accompanied by a ridge over the East China coast, while the pressure gradient north of this latitude is enhanced. Correspondingly, the study region experiences fewer persistent moderate-to-heavy rainfall events. In its negative phase, the pattern in the 500 hPa geopotential height anomaly field is reversed and the study region experiences more persistent moderate-to-heavy rainfall events. This circulation mode is related to both East Asian and Indian summer monsoons. It is also associated with the northward intrusion of the West Pacific subtropical high, the size of the circumpolar vortex over the Pacific, and the impact of the Tibetan Plateau. |
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