analyses and forecast of temperature and moisture rely heavily on satellite
microwave (MW) and infrared radiance (IR) measurements. The resulting operational analyses and forecasts of water vapor and temperature have relatively large uncertainties. This is a significant challenge for producing good analyses and forecasts of tropical storms.
The new GPS radio occultation (RO) observations from the COSMIC satellites since 2006 provide soundings of atmospheric refractivity globally including over tropical oceans. The measurements are not contaminated by clouds or precipitation
and have relatively high vertical resolutions in the lower troposphere.
In this study, we examine the potential of the new RO data to improve the analyses and forecasts of tropical cyclones. Observations of RO refractivity are assimilated in the WRF/DART ensemble filtering system to evaluate the impact of these measurements on analyses and forecasts of tropical storms over the Atlantic
and Western Pacific Oceans. The RO refractivity observations are assimilated
along with radiosodes, satellite cloud drift winds, and AIRS retrieved temperatures using a 36 km resolution WRF model. Results are presented for
hurricane Ernesto and typhoon Shanshan of 2006. The RO observations
significantly reduce the bias of the water vapor analysis and improve the
analyses and forecasts of the intensity and position of the tropical storms.