摘要
利用常规气象观测资料和MODIS卫星C5气溶胶产品,分析了近60年西安日照时数变化特征及其相关影响因子。结果表明,西安日照时数在1981-2001年之间存在明显的下降趋势,以春、夏季日照时数下降最为明显,秋、冬季次之。渭南、华县的日照时数变化表明,西安及其以东地区的日照时数存在区域性下降,且3个城市的日照时数下降百分率存在明显的相关性。而华山(海拔2064.9m)的日照时数在近几十年中并未出现明显的增加或减少趋势,因此,影响西安及其东部日照时数下降的原因很可能位于近地面2km以下。通过分析气溶胶光学厚度、总云量、低云量和降水量的变化,发现关中东部地区的气溶胶光学厚度明显高于西部地区,高浓度的气溶胶并未导致西安、渭南、华县3个城市的总云量、低云量和降水量的增加,相反云量和降水量均呈现弱的区域性下降趋势。因此,西安及其以东地区日照时数的区域性下降不是气溶胶的间接效应引起的,很可能是在地形和盛行风向的共同作用下导致气溶胶在关中东部地区堆积而产生的直接辐射效应所致。
Using the long term record（about 60 years） of meteorological parameters of Xi′an and east of Guanzhong region in Shaanxi Province and nine years of MODIS data,the causes of decreasing trend for sunshine duration during rapid economic developing period have been analyzed.The result shows that there is an obviously decrease of sunshine duration in Xi′an from 1981 to 2001.The decreasing trends are also found in Weinan and Huaxian,east of Xi′an.And there is the good correlation of percentage reduction of sunshine duration at two different stations.But the decrease of sunshine duration is not found in Hua mountain.The cause of the reduction is at height below 2 km.And there is a high value center of AOD on the east side of Guanzhong region in Shaanxi Province,while after eliminating of fog day,total cloud cover and low cloud cover,there are no obvious increase of fog day and cloud cover based on the increase of aerosol caused by the development of the cities.So the main cause of sunshine duration over east of Guanzhong in Shaanxi Province is not the indirect effect of aerosol,but most probably direct radiation.That means in the special terrain and prevailing wind,anthropogenic aerosol caused by the development of cities in Guanzhong region of Shaanxi Province accumulated in east part of Guanzhong,thus there is a high aerosol concentration layer below 2 km above the surface layer.The existence of high concentration aerosol layer could reduce the amount of solar radiation reaching the earth surface and decrease the sunshine duration.The increasing sunshine duration from 2002 to 2008 probably has some relation with anti-pollution measures and variation of prevailing wind,which need further study.
出处
《高原气象》
CSCD
北大核心
2012年第1期185-192,共8页
Plateau Meteorology
基金
陕西省气象局重点项目(2010Z-6)
国家自然科学基金项目(40975020)共同资助
关键词
西安
日照时数
气溶胶
直接效应
间接效应
Xi′an Sunshine duration Aerosol Direct effect Indirect effect
