Retrieval of Total Precipitable Water and Cloud Liquid Water Path from Jason-2 AMR Observations

Abstract

Total precipitable water (TPW) and cloud liquid water path (CLW) retrieval algorithms developed for Advanced Microwave Sounding Unit (AMSU) operational missions are applied to Advanced Microwave Radiometer (AMR)'s measurements on board Jason-2. The channel frequency shift issue, from 31.4 GHz in AMSU to 34 GHz in AMR, is replaced by mapping AMR measurements to AMSU using Simultaneous Nadir Overpasses (SNO). The comparison between our AMR retrievals and Centre National d'Etudes Spatiales (CNES) products using original AMR measurements and the comparison between our AMR retrievals and the TPW and CLW retrieved from AMSU's measurements demonstrate a high consistence, particularly in the TPW retrievals. Our analyses show that 1. large TPW values move northward slowly while the intensities get slightly stronger from April to September then move gradually southward with the intensities becoming weaker from October to March; 2. large values are near tropical region and small values near pole regions which reflect more water vapor with high evaporation, more clouds and precipitations in low latitudes and less water vapor with low evaporation, less clouds and precipitations in high latitudes; 3. there are more water vapor with high evaporation, more clouds and precipitation in summer than in winter; 4. the TPW values are about 100 times larger than those of CLW. The global oceanic monthly, seasonal, yearly composite of TPW clearly illustrate characteristic meteorological features which indicate that such method can be adopted for other microwave instruments with similar frequencies for satellite meteorology applications and satellite climate trend study.