四川盆地气溶胶变化对弱降水的影响:基于干能见度的气候分析

The Effects of Aerosol Variation on Light Rain over the Sichuan Basin: Base on Dry Visibility

降水是气候变化中最主要也是变化较大的因素,相对于较大量级的降水,小量级降水对增暖、气溶胶等因素的变化更为敏感,但目前有关小量级降水与气溶胶相互关系的研究较少.利用1973-2010 年四川盆地及周边46 个气象台站逐日降水、能见度、相对湿度等资料,分析了弱降水（0-1 mm）日数和干能见度资料替代的气溶胶浓度变化趋势及二者可能的关系.结果表明,（1）近38 年来,四川盆地的平均年弱降水日为72.2 d,年平均弱降水日数呈减少趋势,减少率达3.3 d/10 a,盆地的中南部和西部经济发达区域减少明显.（2）盆地半数以上站点的消光系数变化与弱降水日数变化呈负相关,弱降水日数的减少在干能见度低值区（即气溶胶高值区）比干能见度高值区更显著;（3）借鉴降水地形强化因子（Orographicenhancement factor）的概念,提出弱降水变化因子R0（干能见度低值区弱降水日与干能见度高值区弱降水日比值）,R0 反映了气溶胶浓度的差异影响弱降水日数相对变化的程度.弱降水变化因子R0 有逐年减少趋势,弱降水日R0 在38 年间减少了7%,即相较于干能见度高值区,干能见度低值区的弱降水的发生频率较少,这说明气溶胶对于降水的抑制作用在气溶胶高值区较明显.

Precipitation is the major but more variable factor of climate change, light rain is more sensitive to temperature variation and aerosol. By using the daily data of precipitation, visibility and relative humidity observed at 46 weather stations over Sichuan Basin during 1973─2010, we analyzed the long term trend of light rain (0~1 mm) over Sichuan basin, and further discussed the possible relationship between light rain and aerosol variation. The results showed that, (1) precipitation contributed by light rain days exhibits a decrease trend over Sichuan Basin. The annual light rain days is 72.2 day, The decreasing rate of light rain days is -3.3 d/10 a, especially at west and north Sichuan Basin. (2) The variations of Aerosol optical extinct coefficients (AEC) are significantly positive-correlated with light rain days over most area of Sichuan basin, which is especially apparent in the areas with low visibility. (3) The variation factor of light rain days (R0) decrease 7% during the study years, while aerosol burden (represented by visibility in the study) increase, which implied that the reduction of light rain is probably related to the variation of aerosol, i.e. increasing of aerosol suppress light rain over Sichuan Basin.