资源环境科技发展态势分析平台

The Ili River Valley is a trumpet-like terrain facing westward. From west to east, the elevation of the valley floor increases and the width of the valley decreases. Using hourly rainfall data of 2009–2016 obtained from 100 gauge stations over the Ili River Valley, the climatic features of summer regional rainfall events (RREs) are investigated. The mean amount and frequency of rainfall during summer show considerable spatial variabilities in terms of along-valley and across-valley directions. Along the valley, the rainfall gradually increases with increasing elevations. Across the valley, the rainfall also increases from the valley floor to the northern or southern slopes. Three distinct types of RREs are identified: western-local, eastern-local, and eastward-movement RREs. The eastern-local and western-local RREs are located over the east and west of the valley, respectively. The eastern-local RREs have more numbers and longer duration than the western-local ones, resulting in more rainfall in the east than in the west of the valley. In contrast, the eastward-movement RREs with the longest duration initiate from the west of the valley and gradually move to the east of the valley. For these RREs, the spatial distribution of the composite rainfall exhibits a similar pattern to that of the summer mean rainfall. These contribute to more than half of the summer total rainfall in most stations. It is found that the circulation structure accompanying the eastward-movement RREs exhibits a consistent feature with that of the Central Asia vortex/trough systems, and the eastward movement of the entire circulation system is in correspondence with that of the rainfalll center.