Analysis of Temporal and Spatial Distribution Characteristics of Precipitation from May to September in Helan Mountains and Its Relationship with Topography Based on CLDAS Data
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Abstract:
Fine observation of precipitation in mountainous areas is limited by many factors. To understand the distribution characteristics of precipitation in the Helan Mountains region and its relationship with the terrain, we are applying the hourly CLDAS integrated grid precipitation data from May to September, 2008 to 2016, based on availability, evaluating and verifying, to analyse the spatial and temporal distribution characteristics of precipitation in the Helan Mountains region. The results show that: (1) The CLDAS precipitation data are basically consistent with the measured precipitation, can be applied to analyse the precipitation characteristics in the Helan Mountains region. The CLDAS precipitation data tend to underestimate precipitation when heavy rainfall events occur. (2) Precipitation in the Helan Mountains is more abundant in the eastern and southern regions and less in the western and northern regions. The maximum precipitation centre exceeding 240 mm is located at the 0.1 longitude position west from the main peak of the Helan Mountains, and the maximum daily precipitation tends to be higher in the western region than in the eastern region. (3) Most precipitation tends to occur in August, with precipitation in August accounting for 25.6% of the total precipitation from May to September, with July and September being the second and third highest months for precipitation. Short-term heavy precipitation mostly occurs in August, constituting up to 56.4% of the total number of short-duration heavy precipitation events from May to September. Most precipitation occurs from 11:00 to 18:00 on a daily basis, and most short-term heavy precipitation occurs in the period from noon to midnight. (4) The spatial distribution of heavy and moderate rainfall days in the Helan Mountains is basically consistent with the distribution of total precipitation, indicating an overall spatial distribution of high in the east and low in the west, and high in the south and low in the north. The predominant precipitation process in the Helan Mountain is the light rain, then followed by moderate rain. The proportion of moderate rain and light rain processes accounts for 85% of the total regional precipitation processes, and the contribution of heavy rain process is significant. (5) The precipitation in the Helan Mountains tends to increase with the increase of altitude, and the precipitation increasing rate is 5.1 mm/hm in the west slope and 2.1 mm/hm in the east slope. The precipitation increasing rate along with altitude is evidently higher on the west slope than that on the east slope; the correlation between the number of moderate rain days and the terrain height is good, while the correlation between the number of rainy days at other levels and the terrain is relatively weak.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.