Extended Abstract

3 rd Conference on QPE /QPF and Hydrology. World Meteorological Organization, Nanjing, China, Oct.18-­‐22,2010. 2. MethodologyIn order to obtain an accurate radar QPE in the currentstudy was generated with the following 5 steps:1), Minimizing ground clutter contaminations in the QPEthrough a reflectivity quality control (QC);2), Reducing QPE errors due to orographic process,bright band, and radar beam sampling in the ice regionsthrough a VPR correction;3), Mitigating discontinuities in the QPE due to beamblockages through a new way of deriving the hybrid scanreflectivity;4), Mosaicing HSR fields from multiple radars on to acommon QPE analysis grid;5), Reducing QPE errors by applying spatially varying Z-R relationships representing different microphysical processesacross the analysis domain.The current study, we mainly focused on step2developing a robust and effective VPR correction algorithm.This module is an extension of the technique developed byZhang and Qi 2010 (hereafter, ZQ10), in which radar QPEerrors associated with a bright band were corrected usingsingle tilt apparent VPRs. The detailed VPR correctionscheme is discussed in the rest of this section.2.1 Generate apparent vertical reflectivity profile (AVPR)The first step of the new VPR correction involescomputing apparent VPRs by taking azimuthal mean ofreflectivities from predefined precipitation areas with potentialbright band contamination (ZQ10) and with radar sampling inthe ice region. Each AVPR is computed for an individual tilt,and the areas are delineated according to the followingcriteria: 1) VIL (vertically integrated liquid, Greene and Clark1972) =15dBZ and composite reflectivity > 30dBZ (tocapture bright band peak) for bright band areas; 4) Reflectivity> 0 dBZ or composite reflectivity >30 dBZ for ice regions.Fig.2 The conceptual VPR model used in the current study. The blue dots represent the observed VPR, and the red line is theidealized VPR. The blue lines are bright band top (upper) and bottom (below). The solid green and dashed black lines arebright band peak and the 0 o C height, respectively.The orographic enhancement effect (e.g., Kitchen et al.1994) is shown as an increase of areal mean reflectivity withdecreasing height in the mean radar AVPR below the brightband bottom (Fig.2). Vertical pointing precipitation profilerradar data are used to derive the VPR slope for the orographiceffect in the current study. The profiler data were obtainedfrom two S-band precipitation profiler radars deployed duringthe National Oceanic and Atmospheric Administration(NOAA) Hydro-meteorological Test-bed (HMT,http://hmt.noaa.gov) in Nov. 2005 to Apr. 2006. The radarswere located in Cazadero (CZC) near the west coast ofCalifornia and in Alta (ATA) on the California Sierras asshown in Fig.1. These profiler radars measure time evolutionsof the reflectivity structure along a vertical column with high-447-