LAND-SURFACE MODELING AND LAND DATA ASSIMILATION IN THE NCEP MESOSCALE ETA MODEL

Ken Mitchell, Ying Lin, Curtis Marshall, Mike Ek,

Dag Lohmann, Pablo Grunmann, Geoff Manikin, Eric Rogers

Over the past several years, EMC has joined with NWS hydrologists in the Office of Hydrology (OH), land-surface remote sensing experts in NESDIS, and numerous GCIP and GEWEX investigators to develop, test, and operationally implement a series of advancements to the land-surface and hydrology physics of the NCEP mesoscale Eta model and its associated Eta-based 4-D Data Assimilation System (EDAS).

On 03 June 98, NCEP operationally implemented continuous cycling of soil moisture and temperature in the coupled EDAS. To date (Nov 99), this continuous land-surface cycling employs no nudging of soil moisture, as no strong signals of undue soil moisture drift have yet emerged. This year we focused on expanding our capabilities to use GCIP-sponsored GOES-based satellite retrievals of land-surface skin temperature and traditional shelter observations of 2-m air temperature and humidity to monitor drift, which we now do on a systematic monthly basis over 6-13 sub-regions of the U.S.

The continuously cycled soil moisture in the coupled Eta/EDAS is obviously sensitive to whatever systematic biases exist in the coupled EDAS accumulated precipitation patterns. To eliminate any such biases, we finished the final testing stages of our prototype EDAS hourly precipitation assimilation system, which uses our GCIP-supported, realtime, hourly, 4-km Stage IV radar/gauge analyses of precipitation.

Important companion research and development was carried out in our complimentary initiatives in UNCOUPLED land-surface modeling. These included

a) physical refinements in the areas of frozen soil, snowpack, ground heat flux, canopy and atmospheric resistance,

b) a major new collaborative initiative (with OH, NASA/GSFC, NESDIS, and several universities) in a national domain, realtime, hourly, 15-km uncoupled Land Data Assimilation System (LDAS), and

c) c) public availability of a "community" version of the NCEP land-surface model, now formally called the "NOAH LSM".