五台山区地形雨减少与能见度减小的可能联系

Possible Relation of Decreasing Orographic Precipitation with Declining Visibility in the Wutai Mountain Region

为了揭示气溶胶对地形雨的影响,以五台山站为研究站,其南部山下的原平、阳泉为对比站,采用相关性分析研究五台山站与对比站年降水量、降水日数的比值与能见度的关系。结果表明,五台山区能见度显著降低,年降水量及降水日数显著减少;研究站与对比站的年降水量比值、年降水日数的比值均显著减小,并且与能见度显著正相关(p<0.05)。究其可能原因,能见度的降低反映出气溶胶浓度的增加,气溶胶浓度的增加抑制了山区地形雨的形成。山区地形雨的减少导致山区水资源的减少;在缺少山顶站的情况下无法捕捉地形雨减少对面平均降水量计算的影响,导致低估面平均降雨量的减少量,低估山区水资源的减少量。

Based on the observations of precipitation and visibility ranges from 1961 to 2005 at the top of the Wutai Mountain, the ratios between the precipitation amount at Wutai Mountain and at the nearby plain stations （Yuanping and Yangquan）, together with the relation between visibility and aerosol concen- tration were analyzed to reveal the effect of aerosols on orographic precipitation. Over the Wutai Mountain region, visibility, together with precipitation and number of wet days have a significant decline. Precipita tion amount and number of wet days at Wutaishan Station, which are much larger than those the plain sta- tions. Further, the ratios of precipitation amount, and numbers of wet days and the days with precipitati- on less than 5 mm between Wutaishan Station and the contrast stations also have a significant decline, which has a significant correlation （p^0.05） with visibility. It can be speculated that declining visibility indicates enhancing aerosol concentration, which possibly suppresses orographic precipitation. Decreasing orographic precipitation results in declining water resources in mountain regions; if no precipitation gauges at the top of peaks, the precipitation monitoring network can not capture the effect of declining orographic rainfall on areal precipitation, which leads to an underestimation of the decrease in areal precipitation, as well as water resources.