Estimating of atmospheric parameters on land using AMSR-E, part I: Inferring precipitable water vapor

This paper presents a new scheme to retrieve precipitable water vapor (PWV) over land using AMSR-E brightness temperatures (TB) without the help of ancillary data. A surface emission model, Advanced Integral Equation Model (AIEM) and an one-dimensional atmosphere transfer model (1DRTM) were combined to generate a database. Through analysis of the simulated dataset, it is found that the ratio of the polarization difference obtained from 23.8 and 18.7 GHz (ΔTB(23.8) / ΔTB(18.7), called PDR_PWV later) is sensitive to PWV. Compared to the GPS results, the RMSE of our algorithm is 9 mm. There are regional consistency between the results from MODIS and our algorithm. Furthermore, on the surfaces covered by cloud where MODIS cannot be used to retrieve PWV, our algorithm can also give reasonable results.