HR: 14:40h
AN: G13A-04    [Abstracts]
TI: Impact of GPS-Based Water-Vapor Data on Quantitative Precipitation Forecasts in Southern California
AU: * Marcus, S
EM: steven.marcus@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
AU: Kim, J
EM: jkim@atmos.ucla.edu
AF: University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095
AU: Chin, T
EM: mike.chin@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
AU: Danielson, D
EM: David.Danielson@noaa.gov
AF: National Weather Service Forecast Office, 520 North Elevar Street, Oxnard, CA 93030
AU: Jacobson, C
EM: Chris.Jacobson@noaa.gov
AF: National Weather Service Forecast Office, 520 North Elevar Street, Oxnard, CA 93030
AU: Laber, J
EM: Jayme.Laber@noaa.gov
AF: National Weather Service Forecast Office, 520 North Elevar Street, Oxnard, CA 93030
AB: Cold season flash flooding is one of the leading natural hazards in southern California. Although overall precipitation is relatively small, this region is characterized by a high frequency of heavy downpours during the wet season that, in conjunction with steep topography, often causes massive flash flooding. As many of the densely-populated areas are located in valleys and on surrounding hillsides, heavy precipitation events that last only a few hours can cause substantial amounts of damage. In fact, of the 10 highest 24-hour rainfall totals in California, all 10 have occurred in southern California. Hence, accurate quantitative precipitation forecasts (QPF) are crucial for mitigating hazards due to flash flooding in this region. For improving QPF in southern California, a fine-resolution numerical weather prediction model and accurate initial water vapor data are crucial. The Southern California Integrated GPS Network (SCIGN) can provide local precipitable water vapor (PWV) data at high spatial and temporal resolution and is a cost-effective source of water vapor data for improving regional QPF. In this study, we examine the impact of additional water vapor data obtained from the SCIGN array on regional QPF in southern California. Comparison of regional simulations generated with and without GPS-PWV data in a number of case studies shows that the additional GPS-derived water vapor data tends to improve QPF compared to simulations initialized with only NCEP/ETA operational forecast data. It is also found that due to the limited spatial coverage of the SCIGN array, in particular the lack of GPS receivers over the adjacent Pacific, the impact of the GPS-PWV data on regional QPF lasts for only the first 6 hours after initialization.
DE: 3333 Model calibration (1846)
DE: 3354 Precipitation (1854)
DE: 3355 Regional modeling
DE: 3360 Remote sensing
SC: Geodesy [G]
MN: Fall Meeting 2005