High-resolution coupled land data assimilation in a mesoscale real-time forecast system

In the past five years, the National Center for Atmospheric Research (NCAR) and the Army Test and Evaluation Command (ATEC) have been developing a multi-scale (with grid sizes of 0.5-45 km), rapidly cycling (at time intervals of 1-12 hours), real-time four-dimensional data assimilation and forecasting (RTFDDA) system. The RTFDDA system is based on the PSU-NCAR MM5 model and uses continuous data assimilation that employs the forecast model with Newtonian relaxation terms. The atmospheric model is coupled to the Noah land surface model. One of the latest additions to the RTFDDA system is the development and implementation of a high resolution land-surface data assimilation (HRLDAS) system that provides a continuous analysis of the land-surface state for each of the model domains. This paper describes the implementation of such a system and the validation of the mesososcale model analysis and forecasts with and without the use of assimilated land surface conditions.