Comparison Between Satellite Observed and Dropsonde Simulated Surface Sensitive Microwave Channel Observations within and Around Hurricane Ivan

Microwave satellite observations provide useful information about atmospheric temperature and water vapor. This insight could be used to improve hurricane forecasting through the assimilation of this data into Numerical Weather Prediction (NWP) models. Brightness temperature observations can be assimilated into NWP model by using a Radiative Transfer Model (RTM) to convert satellite data into conventional meteorological data. To determine if an RTM is useable in an environment such as a hurricane in which hydrometeors are present in large quantities, a comparison of RTM simulated to observed brightness temperatures is necessary. This comparison is a preliminary step in the overall process of data assimilation in the effort to improve hurricane forecasting. The Joint Center for Satellite Data Assimilation (JCSDA) Community Radiative Transfer Model (CRTM) is used to simulate two sets of brightness temperatures for channels 1–6 and 15 of the Advanced Microwave Sounding Unit–A (AMSU–A) within and around Hurricane Ivan. One simulation is run using dropsonde profiles as input and another simulation is run using model data from the Global Forecast System (GFS) to produce two sets of simulated brightness temperature data. The two simulated brightness temperature data sets are compared to actual AMSU–A observations of Hurricane Ivan as well as to each other. Brightness temperatures simulated using the more realistic atmospheric profiles of the dropsonde data compared more favorably with AMSU–A observation than did the GFS simulations, indicating the potential usefulness of the CRTM to produce surface-sensitive AMSU–A channel observations to improved hurricane forecast.