JP2.1
Case studies of land atmosphere interaction within the 12km North American land data assimilation system (NLDAS-E) project
Charles J. Alonge, NASA/GSFC and SAIC, Greenbelt, MD; and B. A. Cosgrove
A continental scale land data assimilation system project (NLDAS-E) featuring a 12km resolution and operating on the Arakawa E grid has been developed at the NASA Goddard Space Flight Center. Led by NASA GSFC with support from NOAA NCEP, the NLDAS-E project centers on the initialization of the land surface fields of NCEP's mesoscale 12km coupled workstation Eta model. This system aims to supply the Eta model with accurate, unbiased and uncoupled initial land surface conditions on its native Arakawa E grid. NLDAS-E project highlights include: 1) Generation of land surface states over the North American domain, with and without application of land data assimilation techniques, 2) Initialization of the NCEP workstation Eta model with uncoupled NLDAS-E states and internally cycled Eta land surface states, 3) Verification of workstation Eta model forecasts using NCEP's forecast verification system to determine impact of initialization with NLDAS-E conditions, and 4) Case studies to showcase the effects of uncoupled initialization of land surface states.
To assess the impacts of NLDAS-E generated land surface states on Eta model guidance, a thorough benchmarking effort has been performed on two separate test periods during the winter and spring of 2003. These test periods include the ten days between February 16-25, 2003 and the extended tornado outbreak of May 3-11, 2003. An extensive evaluation of retrospective Eta model forecasts using NCEP's forecast verification system for both periods has shown significant improvement in select forecast fields and little to no improvement in others. An overview of the benchmarking efforts and an evaluation of NLDAS-E soil moisture and temperature fields used to initialize the Eta model will be presented. In order to better illustrate the impacts of uncoupled initialization, individual Eta forecasts are evaluated against available observations in order to identify the mechanisms responsible for both forecast improvements and degradations within the May 2003 test period. In addition to evaluating standard meteorological variables, we have also examined severe weather forecast parameters from Eta model output to assess the impact NLDAS-E initialization has on these fields. Examples of observational data used in verifying the individual cases include standard surface synoptic/metar reports, NEXRAD Level II/III radar products, GOES downward shortwave radiation data, and severe weather reports from the Storm Prediction Center. Project data and additional information concerning NLDAS-E can be obtained from http://ldas.gsfc.nasa.gov.
Joint Poster Session 2, Land-Atmosphere Interactions, Part II
Wednesday, 23 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B
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