Advancing Assimilation of Microwave and Radar Observations in the NWP Models

Accurate prediction of tropical cyclones remains a major challenge for numerical weather prediction, particularly for storm intensity, structure, and track. Progress depends on effectively assimilating both passive and active microwave observations, which together provide complementary insights into atmospheric temperature and moisture, cloud microphysics, and precipitation. Passive microwave measurements from low-Earth orbiting satellites, including those in low-inclination orbits, provide frequent sampling that is particularly valuable for tuning temperature and water vapor initial conditions. Observing system experiments with NOAA’s Hurricane Analysis and Forecast System (HAFS) and NASA’s Global Earth Observing System (GEOS) show that assimilating these data leads to more realistic storm structures and measurable improvements in forecasts of intensity and track.

Spaceborne radar observations provide vertical detail on clouds and precipitation. Instruments such as the GPM Dual-frequency Precipitation Radar and EarthCare’s Cloud Profiling Radar are now supported in the Community Radiative Transfer Model (CRTM) through a new spaceborne radar forward model and a Discrete Dipole Approximation–based scattering database. These capabilities are being implemented and tested within the Joint Effort for Data assimilation Integration (JEDI) framework, developed collaboratively by JCSDA, NASA, NOAA, and international partners. Early results from experiments assimilating GPM-DPR observations within NOAA’s GEOS system and CloudSat CPR data within NOAA’s HAFS demonstrate improvements in the analysis of cloud and precipitation structures.