HR: 08:30h
AN: H21J-03 INVITED    [Abstracts]
TI: Evaluation of High Resolution Precipitation Products in Northwest Mexico during the North American Monsoon Experiment (NAME)
AU: * Gochis, D J
EM: gochis@rap.ucar.edu
AF: National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80307, United States
AU: Nesbitt, S
EM: snesbitt@uiuc.edu
AF: University of Illinois at Champaign-Urbana, 105 S. Gregory Street, Urbana, IL 61821, United States
AB: This study examines the spatial and temporal variability of the diurnal cycle of clouds and precipitation tied to topography within the North American Monsoon Experiment (NAME) Tier-1 domain during the 2004 NAME Enhanced Observing Period (EOP, July-August). We focus on the implications for high resolution precipitation estimation and hydrologic studies within the core of the monsoon. Ground-based precipitation retrievals from the NAME Event Rain gauge Network (NERN) and CSU/NCAR version 2 radar composites over the southern NAME Tier-I domain are compared with satellite rainfall estimates from the CMORPH, TRMM 3B42, and PERSIANN operational satellite estimates to examine timing and magnitude differences in their representation of the diurnal cycle along the western slopes of the Sierra Madre Occidental (SMO). Gauge and radar data are examined alongside hourly images of high resolution 11-μm brightness temperature from GOES and cloud to ground lightning flash rates from the North American Lightning Detection Network to investigate diurnally- evolving cloud structures and inferred microphysics. Over high terrain, it is found that convection is relatively shallow (in terms of the depth of mixed-phase processes), although precipitation and lightning often occur near or just after noon local time. It is hypothesized that this shallow cloud and mixed-phase depth tends to contribute to an underestimation of precipitation from both IR and microwave precipitation algorithms. Once the convection has evolved or propagated into lower elevations (around 1500 LT) where more moisture is available, deep, tropopause-depth convection according to IR cloud top temperatures results producing a maximum of lightning and rainfall. Thereafter, organized, deep convection at times propagates onto the coastal plain in the form of mesoscale convective systems where it typically dissipates, although longer lasting deep convection is occasionally observed to propagate out across the Gulf of California. At lower elevations, high sub-cloud evaporation rates and cirrus shielding appear to be contributing to a relative overestimate of precipitation by non- gauge corrected microwave and infrared-based satellite rainfall algorithms; radar estimates showed better correspondence with gauges, presumably due to a lower radar beam height above ground. The remotely sensed precipitation products were then used to drive an operational land surface model in order to assess their relative impacts on runoff, soil moisture and surface energy flux partitioning. The impact of the error structures of key precipitation characteristics (duration, intensity and frequency) from the various products on modeled surface hydrologic variables is found to be significant. Based on these analyses recommendations on future precipitation monitoring for the North American Monsoon system are made.
DE: 1833 Hydroclimatology
DE: 1840 Hydrometeorology
DE: 1847 Modeling
DE: 1854 Precipitation (3354)
DE: 1855 Remote sensing (1640)
SC: Hydrology [H]
MN: 2007 Fall Meeting