Evaluation of GPM candidate algorithms on hurricane observations

The observation of precipitation on a global scale by the Tropical Rain Measuring Mission (TRMM) precipitation radar (PR) and has enabled a large scale study of precipitation over ocean, especially tropical storms. The three-dimensional downward-looking observation characteristic of the TRMM-PR makes it possible to study the vertical structure of tropical storms. The global precipitation measuring mission (GPM) will be the second mission following the success of TRMM. The GPM Mission extends tropical storm tracking and forecasting capabilities into the middle and high latitudes, covering the area from 65° S to 65°N. This orbit will provide new insight into how and why some tropical storm intensify and others weaken as they move from tropical to mid-latitude systems. The GPM core satellite will be equipped with a dual-frequency precipitation radar (DPR) operating at K_u (13.6 GHz) and K_a (35.5 GHz) band. DPR on aboard the GPM core satellite is expected to improve our knowledge of precipitation processes relative to the single-frequency (K_u band) radar used in TRMM by providing greater dynamic range, more detailed information on microphysics, and better accuracies in rainfall retrievals. New K_a band channel observation of DPR will help to improve the detection thresholds for light rain and snow relative to TRMM PR [1]. The dual-frequency signals will allow us to better distinguish regions of liquid, frozen, and mixed-phase precipitation. In the GPM era, storms could be better tracked and characterized. In support the NASA GPM mission, NASA JPL (Jet Propulsion Lab) developed the 2nd generation Airborne Precipitation Radar (APR-2) as a prototype of advanced dual-frequency space radar which emulates DPR on board the GPM core satellite before it is launched. GRIP (Genesis and Rapid Intensification Processes) is the most recent campaign of APR-2 conducted in the year 2010 located in Golf of Mexico and Caribbean sea with the major goal to better understand tropical storms and hurricanes. In this paper, the performance of GPM candidate algorithms [2][3] to perform profile classification, melting region detection as well as drop size distribution retrieval for hurricane Earl will be presented. This analysis will be compared with other storm observations that are not tropical storms. The philosophy of the algorithm is based on the vertical characteristic of measured dual-frequency ratio (DFRm), defined as the difference in measured radar reflectivities at the two frequencies. It helps our understanding of how hurricanes such as Earl form and intensify rapidly. Reference [1] T. Iguchi, R. Oki, A. Eric and Y. Furuhama, "Global precipitation measurement program and the development of dual-frequency precipitation radar," J. Commun. Res. Lab. (Japan), 49, 37-45.2002. [2] M. Le and V. Chandrasekar, Recent updates on precipitation classification and hydrometeor identification algorithm for GPM-DPR, Geoscience science and remote sensing symposium, IGARSS'2012, IEEE International, Munich, Germany. [3] M. Le ,V. Chandrasekar and S. Lim, Microphysical retrieval from dual-frequency precipitation radar board GPM, Geoscience science and remote sensing symposium, IGARSS'2010, IEEE International, Honolulu, USA.