Comparison of MODIS Atmospheric Water Vapor Retrieval, Meteorological Models Tropospheric Delay Estimation with the Results Derived from GPS

摘要

In order to assess the competence of the MODIS near-infrared water vapor retrieval and ground meteorological model estimation for correcting atmospheric effects on InSAR measurements, coincident observations obtained from GPS measurements at five sites in Fangshan Beijng over a month period are used for time series and spatial comparisons. Comparisons of atmospheric water vapor between MODIS and GPS show that their correlation coefficients is higher than 0.97 and standard deviation is about 2.76mm although MODIS appeared to overestimate atmospheric water vapor against GPS. A linear fit model was used to correct MODIS atmospheric water vapor, and better agreements between corrected MODIS and GPS results have been achieved with a standard deviations about 0.78mm. In addition, a first simulate differential comparison of GPS and MODIS atmospheric water vapor before and after model correction was performed using above data, and the standard deviations is 1.75mm before correction and 1.55mm after correction. Finally, we estimated the wet component of the tropospheric delay from the ground meteorological data obtained at the five GPS sites. The results of the Saastamoinen (1972) and Baby et al. (1988) model relative to those of the GPS show that the both two models have the lower correlation with GPS. Correlation coefficients are 0.73 and 0.74 respectively and the standard deviations are both higher than 30mm.