| Characteristics of temporal and spatial variation of surface humid index in East Gansu |
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| DOI：10.7606/j.issn.1000-7601.2008.04.46 |
| Key Words: East Gansu surface humid index aridity temporal and spatial distribution |
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| Abstract: |
| Using the average temperature and monthly precipitation data of three representative stations whose climate change can denote the climatic pattern of East Gansu the spatial and temporal characteristic of surface humid index was analyzed from 1971 to 2005．The results show that the mult-i annual mean index of the surface humid changes in Zhengning in the southeast is the most significant then is that in Xifeng in the middle while that in Huanxian in the north is the least presenting a characteristic of gradual spatial variation to drought from the southeast to middle to north．The surface humid index in southeast area Zhengning and the middle Xifeng reduces by 0．0028／a and the 0．0034／a speed the surface tends to does the desiccation while that in the north Huanxian increases by the 0．005／a speed and the surface moist degree increases．The surface humid index season distribution is the smallest in spring then autumn and is the biggest in summer．There is also a tendency of decrease year by year in spring and the autumn with a worsening of drought year by year while it assumes an increase tendency in summer and the surface moist condition is improving．Surface humid index changes are mainly influenced by precipitation and also by the temperature change．When the temperature is high the surface moisture evaporation and evapotranspiration quantity is big and the surface is easy to get dry．When the temperature is low the moisture evaporation and evapotranspiration quantity is small the surface keeps stable. |