Assessment of the TOVS-derived Moisture and Wind Profiles Over the Southern Ocean

TOVS measurements are available globally since July 1978. Its proper use could greatly improve our understanding of the global climate change. In this study, we report assessment results of the TOVS Pathfinder A and NCEP-DOE Reanalysis-2 (R-2) moisture data as compared to the total precipitable water from SSM/I. We found that the spatial distributions of the annual mean statistics of the total precipitable water are similar among SSM/I, R-2 and TOVS Pathfinder A for both the eddy and mean components. However, transient statistics show that the R-2 total precipitable water agrees with SSM/I with a correlation of 0.77 over the Southern Ocean while the TOVS Pathfinder A moisture is almost uncorrelated with the SSM/I data.

Total moisture transport convergence for 1988 over the Antarctic continent is further examined using the R-2 wind and moisture data as well as the moisture retrievals from TOVS Pathfinder A. To gain a better understanding of transient and mean processes on moisture transport, the total moisture transport was decomposed into mean and eddy components. The results suggest that the mean moisture transport component is about the same for both the R-2 estimate and the estimate from the mixed TOVS Pathfinder A moisture and R-2 wind. The computed eddy and total moisture transport convergence over Antarctica for the R-2 data agrees within 10%-15% with previous surface data based estimates as well as other best estimates from model analyses data. However, the eddy component of the mixed TOVS moisture with R-2 wind is about 60%-70% lower than the R-2 result. These differences occur because the eddy moisture amplitude of TOVS Pathfinder A is nearly 40% lower than the R-2 data and also the TOVS moisture has much lower correlation with the R-2 winds. These results reflect the difficulties of TOVS sensors in quantifying synoptic moisture transients due to conditional sampling problems.

Besides the TOVS moisture profiles, we will also report progress in using TOVS temperature retrievals to derive atmospheric wind profiles over the Antarctic continent.