基于CALIPSO数据的沿海区域气溶胶光学特性时空特征

气溶胶可以直接和间接地影响大气辐射,从而对全球气候产生重要影响。利用AERONET地基气溶胶光学厚度观测数据对CALIPSO气溶胶光学厚度数据进行验证,并利用2010年3月至2020年2月的CALIPSO Level 2数据产品分析了沿海区域及两个典型区域(京津区域和珠江三角洲区域)气溶胶光学特性时空分布,通过分析气溶胶光学厚度、消光系数、退偏比和色比得到沿海区域及两个典型区域气溶胶光学特性的变化特征。结果表明:①沿海区域气溶胶光学厚度存在明显的时空分布特征及季节变化规律,整体呈现北高南低的分布; 沿海区域北部气溶胶光学厚度夏季最大,南部春季最大,南、北部夏季气溶胶光学厚度差值最大。②沿海区域北部的天津及河北中部气溶胶消光系数较大,消光范围主要集中在4 km以下,气溶胶色比及退偏比较大; 沿海区域中部秋季和冬季气溶胶消光系数高值范围大于沿海区域北部; 沿海区域南部气溶胶消光系数四季都较小,消光范围主要集中在2 km以下,气溶胶退偏比较小,但气溶胶色比较大。③京津区域气溶胶光学厚度总体高于珠江三角洲区域; 京津区域夏季气溶胶光学厚度平均值最大,珠江三角洲区域春季气溶胶光学厚度平均值最大; 两个典型区域气溶胶光学厚度整体呈下降趋势。④京津区域每年消光系数都偏大,消光系数高值集中于夏季,2017年气溶胶消光系数开始逐渐减少,气溶胶退偏比及色比相对较大,两者随着高度的增加大体上也呈现增加趋势,该区域主要以非球形大颗粒气溶胶为主; 珠江三角洲区域气溶胶消光系数整体小于京津区域,春季气溶胶消光系数较大,气溶胶退偏比较小,粒子偏球形,但气溶胶色比较大,说明粒子颗粒比较大。

Spatial-temporal Variation of Aerosol Optical Properties in Coastal Region,China Based on CALIPSO Data

Aerosols can directly and indirectly affect atmospheric radiation, and thus have a significant impact on global climate. Based on AERONET data, CALIPSO aerosol optical depth was validated; and based on CALIPSO Level 2 data products from March 2010 to February 2020, the spatial-temporal distribution of aerosol optical properties in coastal region and two typical areas(Beijing-Tianjin region and Pearl River Delta region)were analyzed. The variation characteristics of aerosol optical properties in coastal region and two typical areas were obtained by analyzing aerosol optical depth, extinction coefficient, particle depolarization ratio and color ratio. The results show that: ① The aerosol optical depth has notable spatial-temporal distribution features and seasonal variation in coastal region, and the overall values have a higher distribution in the north than that in the south; the northern coastal region has the largest aerosol optical depth in summer, the southern has the largest value in spring, and the aerosol optical depth difference between north and south is the largest in summer.② The aerosol extinction coefficient in Tianjin and central Hebei areas at the northern costal region is large, and the extinction range is within the range of mainly below 4 km, and the aerosol color ratio and particle depolarization ratio are relatively large; the high value range of the aerosol extinction coefficient in autumn and winter in the central costal region is larger than that in the northern costal region; the aerosol extinction coefficient in the southern costal region is small in four seasons, and the extinction range is mainly below 2 km, and the aerosol particle depolarization ratio is relatively small, but the aerosol color ratio is large. ③ The aerosol optical depth in Beijing-Tianjin region is generally higher than that in Pearl River Delta region; Beijing-Tianjin region has the largest average aerosol optical depth in summer, and Pearl River Delta region has the largest average aerosol optical depth in spring; the overall aerosol optical depths in two typical regions show a downward trend. ④ The aerosol extinction coefficient in Beijing-Tianjin region is relatively large each year, and the high value of extinction coefficient is concentrated in summer of each year, and the extinction began to gradually decrease in 2017; the aerosol particle depolarization ratio and color ratio are relatively large, both of which generally show an increasing trend with the increase of height, indicating that it is mainly dominated by non-spherical large particle aerosols in the area. The aerosol extinction coefficient in Pearl River Delta region is generally smaller than that in Beijing-Tianjin region; the aerosol extinction coefficient in spring is larger, the aerosol particle depolarization ratio is relatively small, and the particles are spherical, but the aerosol color ratio is relatively large, indicating that the particles are relatively large.