甘肃河东雨养农业区旬降水变化及其与土壤湿度关系

摘要

利用甘肃省河东雨养农业区分布均匀的13个农业气象试验站1971～2007年的逐日降水量和土壤湿度资料,分析了该区域作物生长期(3～11月)逐旬降水量的空间分布特征、变化趋势及其与相应时段土壤湿度之间的关系.结果表明,近37 a来,河东雨养农业区逐旬平均降水量的空间分布表现为两种主要的形式--南部型和东部型.南部型,降水量的大值区位于雨养农业区的南部,降水量由南向北减少,这种降水分布型发生的机率占37%,主要发生时段在3月上旬到6月中旬;东部型,降水量的大值区位于雨养农业区的东部,降水量由东向西减少,这种降水分布型发生的机率占63%,主要发生时段在6月下旬到11月下旬.近37 a来,3月上旬、4月中旬、9月上旬和11月上旬的降水量呈显著减少的变化趋势,其余旬的降水量的增加或减少的趋势都不明显.旬降水量与相应旬的土壤湿度一般呈显著的正相关关系,但各站土壤解冻时间,以及各站降水量的相对大小对这种相关关系有一定的影响.%Based on the daily precipitation and the soil moisture data from 1971 ～ 2007, analysis is made of the spatial distribution and climatic variability of ten-day precipitation, and the relationship between the change of ten-day precipitation and soil moisture. The data are from 13 meteorological stations over the rain-fed area east of Yellow River in Gansu Province. The results show that the distribution of every ten-day average precipitation presents as two styles, i .e.the southern type and the eastern type. The area with the biggest amount of precipitation is located in the southern (eastern) part of the study area and the precipitation decreases from south (east) to north (west) when the distribution of precipitation shows the southern (eastern) type. In recent 37 yearn, the occurrence probability of southern (eastern) type is 37 (63) percent and the main occurrence period is during the first ten-day in March (last ten-day in June) and the mid ten-day in June (last ten-day in November). The tendency of precipitation change appears significant decreasing for the first ten-day in March, the mid ten-day in April, the first ten-day in September and the first ten-day in October. There exists, in a sense, a significant positive correlation between the ten-day precipitation and the corresponding ten-day soil moisture, while the time of soil thawing and the relative amount of precipitation also have influence on this correlation.