3-DIMENSIONAL AIR-CIRCULATION IN A SQUALL LINE FROM AIRBORNE DUAL-BEAM DOPPLER RADAR DATA - A TEST OF COPLANE METHODOLOGY SOFTWARE

The detailed structure of a tropical squall line observed in central F lorida was investigated from an airborne dual-beam Doppler radar, poin ting respectively fore and aft. This allowed dual-Doppler observations from a straight Eight path in a way similar to the coplane sampling t echnique proposed for two ground-based Doppler radars and for which th e authors had developed an elaborate method in order to obtain a relia ble wind estimation. The application of this analysis method to the ai rborne dual-beam radar observations is discussed, along with the basic requirements due to the specific airborne data sampling. The retrieve d three-dimensional airflow structures within the convective part of t he squall line are found to be quite consistent with those previously documented from ground-based radars, such as the convective-scale down drafts sustaining a well-marked rear-to-front flow or the convective u pdrafts associated with the front-to-rear flow at mid-to-upper levels and that detrain into the rear part of the squall-line system. Moreove r, it is found that the coplane analysis provides a more regular descr iption of the airflow than the conventional Cartesian analysis. The su itability of the coplane approach is also examined by quantifying the uncertainty due to geometric errors that affect the accuracy of the be am pointing.