Study On Channel Selection Of Atmosphere Vertical Sounder (GIIRS) Onboard The FY-4A Geostationary Satellite

Temperature retrieving is indispensable in weather and climate research.In order that,selecting accuracy channels for the retrieval of temperature with hyperspectral data is particularly important.In view of GIIRS,a hyperspectral vertical detector equipped on the FY-4A geostationary satellite,a channel selection experiment for the retrieval of temperature is carried out.Using line-by-line radiative transfer model,according to the information content,channels are selected by step-by-step iterative method,which can be used to describe the effective information of various atmospheric parameters in the infrared hyperspectral data.The selected channels have high information content but small correlation with each other,which can be used as the representative channel set for temperature profile retrieval research and data assimilation.In the FY-4A detection range,2 groups channels for temperature retrieval are obtained when using different profiles,56 channels for USSA(United States Standard Atmosphere)and information content is 69.69%,another group is 58 channels for ECMWF(European Center for Medium range Weather Forecasts)and its information content is 67.22%.Classifying the FY-4A detection range into 24 types according to season,latitude and underlying surface.Rely on this,24 datasets of profiles obtained using statistics.New profile datasets instead of USSA to calculate the Jacobian matrix of temperature in line-by-line radiative transfer model.Finally,with background covariance matrix and channel noise of GIIRS,24 groups of channel selected under different types:(1)The number of channels selected in different seasons is almost the same,but in summer,the information content is always low,which is related to the instability of the atmosphere.There are 30 preferred channels in the four seasons,which are densely located around 4.3 μm.(2)The optimal temperature retrieval channel selected for different latitudes contains more than 60% of information,which is generally high in high latitudes and generally low in low latitudes,while in mid-latitudes is relatively stable.(3)In the same season,the difference in latitude of the atmospheric temperature is greater than that of the ocean over land.When considering information content,the mid-latitudes above land are often greater than those at high or low latitudes,while In the ocean,the situation is opposite.Considering differences in seasons,latitude,and underlying surface.Different channel group can be used for weather and climate research in different period and area,in that way,it can improving the accuracy of temperature retrieving targeted.Finally,using same method and profile on different hyperspectral sensor(CrIS and GIIRS)to select sensitive channels.Comparing the results,it verifies the channel selection method in this thesis is accuracy and the location of the FY-4A temperature detection channel is reasonable.