利用气象能见度作晴空卫星遥感大气订正的一种实用方法

A FEASIBLE METHOD ON ATMOSPHERICAL CORRECTION TO SATELLITE SENSING GROUND ON A CLEAR DAY BY USING METEOROLOGICAL VISIBILITY

介绍了一种方法，它借鉴Ｓｔｒｕｍ［１］的工作利用常规气象能见度资料计算出气溶胶光学厚度值，并且使用系统聚类法进行全国光学厚度场的归类划区、对于晴空卫星地面遥感进行实时大气订正，这种方法是可行和实用的。选用一次强风沙过程对此法作检验，效果相当理想。

It is necessary for amospheric correction, especially for aerosol extinctioncorrection, in processing satellite sensing information, for example, in remote sensing ofthe vegetation index on a clear day. The optical depth of aerosol or spectral transmissivityis an important parameter characteristic of atmospheric aerosol extinction ability. Therehas been no systematic space-time observation to the optical depth of aerosol in China upto now, for the content and space-time variations of atmosphyeric aerosol are considerably complicated. In order to correct the real-time optical depth of atmospheric aerosol wesuggest a computational method of the aerosol optical depth by 'st.ng daily meteorolgicalvisibility data on the basis of Strum's work[1]. this paper we discuss the following pointsof this method:1. It is possible to establish a reasonable relationship between the aerosol opticaldepth and the. meteorolgical visibility by using the profiles of aerosol number density. Theprofiles are quoted from Elterman's work.2. The principal Work steps of the method are as follows: frstly, compute the aerosoloptical depth of vertical layer up to atmospheric top from daily meteorological visisbilities of Station networks in China. Secondly, divide the optical depth fields into some areas bymaking use of system cluster analysis. Finally, compute the region mean of optical depthproviding satellite correction of the region.3. We made an effect test to a severe sandstorm process in North China from 18-20April, 1980. The result was satisfying. The high value region of optical depth basically coincided.with the sandstorm region. The o.ptical depth region strengthened and extendedcorrespondingly along with the sandstorm region.4. This:method is simple, convenient and feasible for real-time atmospheric correction on a clear day. The correcting time by microcomputer is only about ten minutes.5. There are some problems to be improved. Firstly, angstrom index β(or α) in computing formula should be selected exactly according to the patterns of vegetation region.Secondly, Junge aerosol size distribution is one of the theoretical basis of the method. Thecomputing formula of the method must be improved for non-Junge size distribution.Thirdly we must introduce moisture correction to meteorolgical visisbility before opticaldepth computation, for meteorological visbility is closely related to the atmospheric moisture Finally the meteorological visibility must be reduced to sea level when the sea level elevation of meteorological station is above 200m