A Comparison of Two Microwave Retrieval Schemes in the Vicinity of Tropical Storms

The Regional and Mesoscale Meteorology Branch (RAMMB) at the Cooperative Institute for Research in the Atmosphere has developed products which rely on atmospheric temperature profiles derived from measurements of microwave radiation. By using the hydrostatic approximation and a balance condition, these temperature profiles can be used to estimate the wind field in and around a tropical cyclone. Since their development, these products have used temperature profiles derived using the Advanced Microwave Sounding Unit (AMSU)-A measurements in a statistical retrieval scheme. More powerful and flexible methods of creating vertical profiles of the atmosphere are now available, such as the Microwave Integrated Retrieval System (MIRS), the National Environmental Satellite, Data, and Information Service's current operational microwave retrieval system. A comparison of atmospheric profiles derived from the two methods is presented, with dropsondes providing the ground truth. Both methods provide vertical profiles of atmospheric temperature, so a direct comparison with collocated dropsondes is possible. The older, statistical method does not compute the vertical distribution of water vapor, but does compute total precipitable water. Therefore, the comparison of the skill with which the two methods measure water vapor is restricted to the integrated quantity. MIRS does provide water vapor profiles, and these will be compared to the vertical moisture distribution determined by dropsondes. Tropical cyclone intensity estimates derived from the two retrieval techniques will also be examined, with best track data used as ground truth.

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