Characterizing the Different Tropical Rainfall Regimes in Brazil: A Contribution of CHUVA Project

Since 2010 the CHUVA Project(Cloud processes of tHe main precipitation systems in Brazil: A contribUtion to cloud resolVing modeling and to the GPM - GlobAl Precipitation Measurement) is conducting several field campaigns in order to depict the main precipitating systems observed in Brazil. In each experiment, CHUVA deploys one X-Band Polarimetric Radar with several disdrometers (impact and optical), rain gauges and 2 vertical pointing micro rain radars. Until the present moment, 5 field experiments (Alcantara – March 2010; Fortaleza – April 2011; Belem – June 2011; Vale do Paraía – November 2011 trough March 2012; Santa Maria – November-December 2012) were able to evaluate warm and mixed phased systems, sea breeze systems, ITCZ convection, localized convection, squall-lines, frontal systems and even mesoscale convective systems. Although in the tropics, the drop size distribution (DSD) measurements show interesting features like: a) Alcantara shows a strong bi-modal distribution (1.1 and 2 mm) above 60 mm/h while Vale do Paraíba (1.5 and 2 mm) and Santa Maria (0.8 and 1.5 mm) is above 10 mm/h; b) shallow and warm precipitating regimes in Alcantara, Fortaleza and Belém have mean diameter (Do) between 1.58-1.82 while more continental systems (Vale do Paraíba and Santa-Maria) are within 1.18-1.26 mm; c) in terms of liquid water content in 50% of the time, the maritime systems have as much as 4 times more rain water while for rainfall rate is around 2-3 times more. Now taking these measurements to evaluate the surface rainfall rate (R) product version 7 of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) 2A25, we found that coincident DSD measurement within +-1 hours of TRMM orbit and 50 km spatial distribution of PR are: a) in general 2A25 underestimates the rainfall rate for radar reflectivity (Z) values less than 30 dBZ while it overestimates above; b) in terms of volumetric rainfall probability density functions (weighted by the total precipitation amount), 2A25 overestimates as much as 13 to 160% of the median rain rates at Fortaleza, Belém and Santa-Maria and it underestimates in Alcantara. At the higher rain intensities (90% level), 2A25 overestimates as much as 200% at Fortaleza and Belem, while it underestimates by 30-60% at Alcantara and Vale do Paraiba. In addition to these results, during the conference it will be also presented the rain characteristics observed by the X-Band radar (echo top, Z, R, ZDR, thickness of the warm and mixed phase layers distributions) and the quality control of the radar measurements: biases and rain attenuation correction evaluation.