Recent results from the 12km North American land data assimilation system (NLDASE) project

A continental scale land data assimilation system project (NLDAS-E) featuring a 12km resolution and operating on the Arakawa E grid is currently ongoing 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. Featuring multiple LSMs and assimilating multiple land surface quantities, this system will serve to supply the Eta model with accurate, unbiased and uncoupled initial land surface conditions on its native Arakawa E grid. NLDAS-E project goals 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 NCEP standard operational EDAS land surface states, 3) Execution of ensemble forecasts using the NLDAS-E and Eta modeling systems, 4) Verification of workstation Eta model forecasts using NCEP's forecast verification system (FVS) to determine impact of initialization with NLDAS-E conditions. The system will make use of the Noah, CLM2, and Mosaic LSMs, and will utilize standard workstation Eta as well as high-resolution soil and vegetation fields in order to explore the impact that the use of such fields has on NWP forecasts. NLDAS-E research will improve understanding of the interaction between the land surface and the atmosphere from short- to medium-length time scales, will create accurate, high resolution land surface data sets useful for future research and applications, will improve the initialization of the Eta model in a way that may be adapted to additional NWP models in the future, will improve forecast accuracy, and will continue NASA GSFC's efforts in the collaborative NLDAS project.

This AMS presentation will focus on an overview of the NLDAS-E project, and will include a summary of recent progress. Developments include the generation of forcing data sets, Noah LSM output, and workstation Eta forecasts over the entire North American domain used by NCEP's operational Eta model utilizing NASA GSFC's Compaq-Alpha supercomputing platform. NLDAS-E forcing files use 12km EDAS/Eta model output data as a data backbone, and include observed precipitation (CPC gage/Stage II Merged, CMAP, and CMORPH) and observed radiation (AGRMET and GOES) products when available. Four 10-day series of workstation Eta simulations have been conducted and verified for the period of May 1st through May 10th, 2003. Four sets of workstation Eta simulations have been conducted and verified for the period of May 1st through May 13th, 2003. These include a baseline run initialized with NCEP operational land surface conditions, a baseline run initialized with NLDAS-E land surface conditions, and two experimental runs using initial land surface conditions drawn from NLDAS-E simulations which assimilated MODIS snowcover data.

Initial verification results from the NCEP FVS show that NLDAS-E land surface initialization of the workstation Eta model has a generally positive impact on 2-m temperature, 10-m wind, 2-m relative humidity, and precipitation forecast fields out to 84 hours. The largest effects appear in the 2-m temperature and 2-m relative humidity fields. Impacts vary greatly by region and output field, and FVS output will be detailed in the presentation.

Project data and information concerning NLDAS-E can be obtained from http://ldas.gsfc.nasa.gov. This presentation is submitted in conjunction with a complimentary NLDAS-E presentation which will be given by Charles Alonge. Submitted in a separate abstract, this second NLDAS-E talk will focus on verification of specific case study events within the May 1st-May 13th 2003 time period mentioned above, in contrast to the general overview and verification information given in this talk.