A consortium of GAPP-sponsored groups is undertaking the development of an uncoupled North American Land Data Assimilation System (LDAS). NCEP, NASA/GSFC, NWS Hydrology Lab, NESDIS, Princeton University, University of Washington, University of Maryland, and Rutgers University have undertaken the development and prototype real-time demonstration of national, real-time, hourly, 1/8th degree, uncoupled land-surface models forced by observed precipitation and observed GOES-derived solar insolation (See Lohmann et al., this conference). The LDAS project also produced a 5 year retrospective forcing data set (see Cosgrove et al., this conference) from September 1996 to September 2001.

The LDAS forcing is derived from 3 different data sources, with three different initial spatial and temporal scales. Three-hourly AWIPS 212 output from the Eta Data Assimilation System (EDAS), providing surface meteorology; hourly, observed data from GOES satellites (0.5 degree short-wave radiation); WSR88D Doppler radar sites (4km precipitation) blended with data from daily rainfall gauges (1/8th degree precipitation). Forcing data are interpolated from their native resolution to a 1/8th degree, hourly resolution. NOAH model output is hourly on 1/8th degree.

This poster investigates the temporal and spatial scales of the forcing variables (mainly precipitation and solar radiation) and the corresponding response of the state and flux variables of NOAH land surface model, e.g. soil moisture and temperature, evapo-transpiration and runoff. Measures of spatial and temporal characterization are: spatial autocorrelation and cross-correlation functions of precipitation and solar radiation, temporal and spatial autocorrelation function of soil moisture and soil moisture anomalies; evapotranspiration time scales in different climatic zones. An attempt is also being made to propose a classification scheme for the continental United States based on EOFs of certain land surface parameters, which are thought to be widely representative of the hydroclimatology of a region.