Methods that Amalgamate Relative Humidity Data and Their Validation, Based on Satellite and Sounding Data for Eastern China in January 2013

By contrasting the atmospheric relative humidity data in January 2013 from sounding to that from the MODIS (MODerate-resolution Imaging Spectroradiometer) atmospheric profile product, it is found that MODIS relative humidity data are higher than sounding data. Relative humidity data less than 5% from sounding and relative humidity data affected by cloud from MODIS need to eliminate. Before amalgamation, correcting the systematic error by mean revision is necessary. The direct reduction method and maximum correlation coefficient method were used to fuse the two kinds of relative humidity data. Analyzing the fused results and using cross check, the results show that:(1) Relative humidity data from the direct reduction method are higher than those from sounding when in a low relative humidity area, and the opposite when in a high humidity area; relative humidity data from the maximum correlation coefficient method are close to the sounding data in all areas. (2) Compared with sounding data, the error of the amalgamation result generated by the direct reduction method is no more than 10% at 850 hPa, no more than 12% at 925 hPa, and no more than 9% at 1000 hPa; the error of the amalgamation result generated by the maximum correlation coefficient method is no more than 4% at all levels. Overall, the maximum correlation coefficient method is better than the direct reduction method.