A three-dimensional variation (3D-var) retrieval of temperature and water vapor profiles

Abstract
One-dimensional variation retrieval system has been applied for several decades and provided valuable products to a large community for satellite sensor monitoring, climate studies, and quality control in numerical weather prediction (NWP) centers. This paper attempts to use a three-dimensional variation (3D-var) method to further improve the retrieval system. We set up a 3D-var retrieval algorithm based on a Gridpoint Statistical Interpolation (GSI) scheme from the National Center for Environmental Prediction (NCEP). The 3D-var retrieval system can be applied without any conventional observations. In comparison with analysis, the 3D-var retrieved temperature and water vapor profiles are better than background values that are 6-hour forecast. The result implies that 3D-var retrieval system is valuable. Even using climatologic data as the background and the first guess, the 3D-var retrieval system is able to produce a low pressure field at the surface and the warm core at upper troposphere for the typhoon Choi-wan.