X-band Polarimetric Radar Rainfall Measurements in Keys Area Microphysics Project EMMANOUIL N. ANAGNOSTOU Department of Civil and Environmental Engineering, University of Connecticut, Storrs, Connecticut MIRCEA GRECU Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Baltimore, and NASA Goddard Space Flight Center, Greenbelt, Maryland MARIOS N. ANAGNOSTOU Department of Civil and Environmental Engineering, University of Connecticut, Storrs, Connecticut (Manuscript received 11 November 2003, in final form 12 January 2005) ABSTRACT The Keys Area Microphysics Project (KAMP), conducted as part of NASA’s Fourth Convective and Moisture Experiment (CAMEX-4) in the lower Keys area, deployed a number of ground radars and four arrays of rain gauge and disdrometer clusters. Among the various instruments is an X-band dual- polarization Doppler radar on wheels (XPOL), contributed by the University of Connecticut. XPOL was used to retrieve rainfall rate and raindrop size distribution (DSD) parameters to be used in support of KAMP science objectives. This paper presents the XPOL measurements in KAMP and the algorithm developed for attenuation correction and estimation of DSD model parameters. XPOL observations in- clude the horizontal polarization reflectivity Z H , differential reflectivity Z DR , and differential phase shift  DP . Here, Z H and Z DR were determined to be positively biased by 3 and 0.3 dB, respectively. A technique was also applied to filter noise and correct for potential phase folding in  DP profiles. The XPOL attenu- ation correction uses parameterizations that relate the path-integrated specific (differential) attenuation along a radar ray to the filtered- DP (specific attenuation) profile. Attenuation-corrected Z H and specific differential phase shift (derived from filtered  DP profiles) data are then used to derive two parameters of the normalized gamma DSD model, that is, intercept (N w ) and mean drop diameter (D 0 ). The third parameter (shape parameter ) is calculated using a constrained – relationship derived from the mea- sured raindrop spectra. The XPOL attenuation correction is evaluated using coincidental nonattenuated reflectivity fields from the Key West Weather Surveillance Radar-1988 Doppler (WSR-88D), while the DSD parameter retrievals are statistically assessed using DSD parameters calculated from the measured raindrop spectra. Statistics show that XPOL DSD parameter estimation is consistent with independent observations. XPOL estimates of water content and N w are also shown to be consistent with corresponding retrievals from matched ER-2 Doppler radar (EDOP) profiling observations from the 19 September air- borne campaign. Results shown in this paper strengthen the applicability of X-band dual-polarization high resolution observations in cloud modeling and precipitation remote sensing studies. 1. Introduction The primary objective of the Keys Area Microphys- ics Project (KAMP), conducted during National Aero- nautics and Space Administration’s (NASA) fourth Convective and Moisture Experiment (CAMEX) cam- paign in the southern Keys area was to facilitate vali- dation of cloud-resolving and radiative models in tropi- cal oceanic regime. Simulated profiles of cloud and pre- cipitation parameters and corresponding radiative transfer properties are used to build physically based algorithms for precipitation retrieval from satellite pas- sive (radiometers) and active [Tropical Rainfall Mea- suring Mission (TRMM) precipitation radar] micro- wave observations (Smith et al. 1994; Kummerow and Corresponding author address: Emmanouil N. Anagnostou, Dept. of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Road, Storrs, CT 06269. E-mail: manos@engr.uconn.edu JANUARY 2006 ANAGNOSTOU ET AL. 187 © 2006 American Meteorological Society