30th International Conference on Radar Meteorology


Comparison of an easterly and westerly MCS observed during TRMM-LBA using ground-based and airborne data

Andrea G. Williams, Colorado State University, Fort Collins, CO; and S. A. Rutledge

The TRMM-LBA field campaign was conducted in the southwestern portions of the Amazon in January-February 1999. The purposes of the field program were to validate both TRMM satellite algorithms and TRMM cloud models. Many convective systems were sampled with a suite of instruments, including both remote and in situ sensors. In this study we focus on the easterly 17 February 1999 case and a westerly case. We examine dual-Doppler, polarimetric and airborne data in this mesoscale convective system. Radar data were obtained from the TOGA C-band radar, and the NCAR S-pol 10 cm radar. The latter system also collected a full suite of polarimetric variables including differential reflectivity and differential phase. These variables yield information on hydrometeor types and mixing ratios in regions that are difficult to sample with the in-situ aircraft. We also analyze data collected by the NASA ER-2 aircraft, in particular data from EDOP (X-band Doppler radar) and AMPR (Airborne Microwave Profiling Radiometer). The easterly case had strong convective cells exceeding 45 dBz. Polarimetric results showed that some convective cores contained large, oblate raindrops, however, differential phase data indicated that considerable precipitation mass exited in smaller drop sizes. Near the end of this system’s lifetime, a prominent radar bright band was evident along with classic melting signatures in the polarimetric variables. The westerly case is more monsoonal in nature with stratiform precipitation and embedded convection. To compare the radars with the passive microwave instrument, we use the Goddard Cumulus Ensemble model to simulate hydrometeor profiles and a retrieval program to simulate the reflectivity of both the easterly and westerly cases. For another comparison, we use the polarimetric results from S-pol to create hydrometeor profiles for each case and try to re-create the brightness temperature depressions observed from AMPR.

Poster Session 10, Tropical Precipitation—SCSMEX, JAMSTEC, TRMM & Others
Saturday, 21 July 2001, 2:00 PM-3:30 PM

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