CE-318太阳光度计及探空数据反演水汽含量与MODIS近红外水汽产品对比

Comparison of Water Vapor Content Product Retrieved by CE-318 Sun-photometer, Radiosonde Data and MODIS Near Infrared Data

大气水汽含量是遥感定量反演的重要参数。本文利用CE-318太阳光度计,反演了2014年6月至2016年5月南宁市的大气水汽含量,分析其季节变化特征,并将其与探空数据、MODIS近红外水汽产品数据进行相关性分析。结果表明:(1)南宁市大气水汽含量季节变化特征明显:夏季高达4~6 g/cm^2,而冬季则只有2 g/cm^2,与南宁地处亚热带地区有关。夏季该地区季风气候盛行,大气水汽含量高,冬季季风气候减弱,大气相对干燥。(2)CE-318太阳光度计反演的大气水汽含量(PW)与探空数据获取的水汽含量之间存在良好的线性相关,相关系数为0.877,平均绝对误差为0.42 g/cm^2,平均相对误差为10.96%;而MODIS近红外波段反演的水汽精度较低,平均绝对误差为0.74 g/cm^2,平均相对误差为18.74%。

Atmospheric water vapor content is an important parameter for quantitative remote sensing. In this paper, the CE-318 sun-photometer was mounted on top of our building in Nanning, South China to measure the solar irradiance in the pre-set wavelength, i.e. 440 nm, 670 nm, 870 nm, 936 nm and 1020 nm for retrieval of atmospheric water vapor or perceptible water （PW） during June 2014 to May 2016. After calibration, the solar irradiance measurements from the CE-318 Sun-photometer were used to retrieve the atmospheric water vapor （CE-318 PW） for systematical analysis of its seasonal variation during the measuring period. Comparison has been made to correlate CE-318 PW with the radiosonde data and MODIS near infrared water vapor products. The results showed that： （1） the retrieved CE-318 PW in Nanning is characterized with remarkable seasonal variation. High values （4-6 g/cm^2） of the PW were observed in summer. As a contrast, the PW was observed to be relatively low （usually -2 g/cm^2） in winter. This is mainly attributed to the performance of subtropical monsoon in the region. In summer, the monsoon performs actively, making the atmosphere to be wet and hot. In winter, pertbrmance of the monsoon becomes weak, leading to a relatively dry atmosphere dominating the region. （2） Good correlation was found between CE-318 PW and the radiosonde data from meteoroidal station, with correlation coefficient of 0.877, average absolute deviation of 0.42 g/cm^2 and average absolute relative deviation of 10.96%. But the precision of MOD05 PW was low, its average absolute error was 0.74 g/cm^2 and the average relative error was 18.74%.