陇东地表湿润指数的年际变化特征

Characteristics of temporal and spatial variation of surface humid index in East Gansu

利用能够代表陇东气候类型的三个代表站1971-2005年月平均气温和降水资料,分析该地地表湿润指数的时空变化特征。结果表明：地表湿润指数变化多年平均,东南部的正宁最大,中部的西峰次之,北部的环县最小,呈现由东南向中部和北部逐渐干旱的空间变化特征;东南部的正宁和中部的西峰地表湿润指数以0.0028/a和0.0034/a的速率减小,地表趋于干旱化,北部的环县以0.005/a的速率增加,地表湿润程度有所增加;地表湿润指数的季节分布以春季最小,秋季次之,夏季最大,且春季和秋季有逐年减小的趋势,干旱化程度逐年加重,夏季呈增加趋势,地表湿润状况有所改善;地表湿润指数变化主要依靠降水的影响,但同时也受温度变化的影响,温度高,地表水分蒸发蒸散量大,地表易于变干,温度低,水分蒸发蒸散量小,地表不易变干。

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 multi-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.