利用水平面太阳直接辐射日曝辐量反演大气气溶胶光学厚度的方法研究

A Study of Retrieving Aerosol Optical Depth from Daily Horizontal Broadband Direct Solar Radiation

本文发展了一个从宽带水平面太阳直接辐射日曝辐量(总辐射与散射辐射日曝辐量之差)反演光谱大气气溶胶光学厚度的方法,包括建立一个"等效"的瞬时太阳天顶角模型,并提出了一个基于气溶胶标高的云影响甄别方法。对该反演方法的数值模拟和误差分析表明:"等效"瞬时太阳天顶角模型的不稳定性引起的光学厚度反演误差平均为3.66%;光学厚度日变化对一段较长时间的平均光学厚度的影响不显著;订正造成的散射辐射误差≤20%时,光学厚度平均偏差≤4%。通过与AERONET产品的比对验证表明:本文发展的光学厚度反演方法和云影响甄别方法都是有效的;晴空反演的0.75μm光学厚度与AERONET的相关系数超过0.95,平均误差约0.02;云甄别方法计算的季节和年平均光学厚度与AERONET具有较好的一致性。

A method of retrieving aerosol optical depth （AOD） is developed using daily horizontal broadband direct solar radiation,including an ＂equivalent＂ instantaneous solar zenith angle model. Furthermore,a cloud-contaminated reduction method,which is based on aerosol scaling height,is proposed to calculate monthly mean AOD. Numerical simulation and error analysis show that：1） The mean value of AOD retrieving errors due to instability of the ＂equivalent＂ instantaneous solar zenith angle model is 3.66%, 2） AOD diurnal variation has little influence on the mean value of AOD for a relatively long time, 3） the AOD retrieving error is less than or equal to 4% when the error of diffuse solar radiation is less than or equal to 20%. A comparison between AODs retrieved from this method and the AERONET shows that the AOD retrieving method and the cloud-contaminated reduction method are both effective. The correlation coefficient and mean bias error between AODs from this method and the AERONET at 0.75 μm in clear days are 0.95 and 0.02,respectively. With the cloud-contaminated reduction method,the seasonal and yearly mean AODs show a good consistent with those from AERONET.