近50年来中国西北地区干湿状况时空分布

根据西北地区77个气象台站气候资料,并利用改进的Penman公式,计算了该地区1958年~2001年的44年平均潜在蒸散量的时空分布,并分析了与降水量变化之间的关系,得到4种类型潜在蒸散量与降水量年际变化的组合分布型。其中年平均潜在蒸散量减小而年降水量增大的组合占研究区站点总数的40%以上。分析潜在蒸散量及观测蒸发量与各气候因子的相关性,发现干旱区的蒸发与太阳辐射和风速有关。定义干燥指数为潜在蒸散量与降水量的比值,用来描述西北干旱区的干湿状况。对干旱区四个季节(春、夏、秋、冬)干燥指数近50年的线性变化趋势分析结果显示,干旱区春季大部分区域干燥指数呈增加趋势,即趋于变干;夏季大部分地区趋于变湿,但仅在新疆东部和甘肃西部较为明显;秋季新疆大部、甘肃西部和青海北部等地区趋于变湿,而干旱区东部区域则趋于变干。冬季干旱区大部分区域趋于变湿,只有新疆西南部和西北部及东部部分地区、甘肃西部和内蒙西部等地有变干趋势。

The Temporal and Spatial Distribution of Surface Dry-wet Conditions over Northwestern China in Recent 50 Years

Based on the climate data of 77 meteorological stations covering 1958-2001 in northwestern China (the area is within the north of 35oN and west of 105oE in China), and using the integrated Penman formula, the mean potential evapotranspiration (PE) in our study area is calculated. Four patterns of variations of PE and precipitation were detected, showing that the solar radiation and wind speed are two main reasons responsible for the evaporation in the arid area. The aridity index is defined to the ratio of PE and precipitation and is used to describe distribution of the wet-dry conditions in northwestern China. The linear regression trends of the aridity index for the last 50 years show that there are a drying trend in spring and a wetting trend in summer (pronounced only in east Xinjiang and west Gansu) over large parts of the arid areas, and a wetting trend in autumn in most parts of Xinjiang and west Gansu as well as north Qinghai, and in winter, part of the arid area tends to be wetter, and only parts of Xinjiang, Gansu and Inner Mongolia tend to be drier.