Application of NCEP Land Data Assimilation Systems for Global and Regional Drought Analysis, Monitoring and Prediction

Currently, NCEP/EMC includes three Land Data Assimilation Systems (LDASs): (1) Global LDAS (GLDAS), (2) North American LDAS (NLDAS), and (3) high resolution NLDAS on the Hydrologic Rainfall Analysis Project (HRAP) grid (HRAP-NLDAS). GLDAS was developed to provide initial conditions for NCEP coupled global weather and climate models, NLDAS to provide hydrometeorological products to support the National Integrated Drought Information System (NIDIS), and HRAP-NLDAS for long-term and near real-time high-resolution (~4 km) hydrometeorological products to support hydrological research and application at National Weather Service (NWS) River Forecast Centers and the Office of Hydrologic Development (OHD). These three systems are independent but closely related. The core model of the three systems is the NCEP operational land surface model (Noah) and the OHD operational hydrological model (SAC-HT); two additional land surface/hydrological models are used in NLDAS. The three systems are all moving towards being used for global and regional drought analysis, monitoring and prediction.

The uncoupled GLDAS used the Noah land model in the Climate Forecast System Reanalysis (CFSR), with blended atmospheric model and observed precipitation forcing used to generate long-term (1979-present) global hydrometeorological products (at ~38 km) as part of the proposed Global Drought Information System (GDIS) in association with the NOAA Climate Program Office (CPO) Modeling, Analysis, Predictions and Projection (MAPP) Drought Task Force; use of GLDAS/Noah continues in the operational Climate Forecast System version 2 (CFSv2). NLDAS is a quasi-operational system that supports U.S. operational drought monitoring and seasonal hydrological prediction, in particular for NIDIS. One key application of the near real-time updates is drought monitoring over the Continental United States (CONUS), shown at the “NLDAS Drought” tab of the NLDAS website (www.emc.ncep.noaa.gov/mmb/nldas). NLDAS is mature, with NCEP operational implementation planned for the near future. At the same time, the NCEP/EMC NLDAS team is collaborating with the NASA Goddard Hydrological Sciences Laboratory to add their Land Information System (LIS) to the current NLDAS which will allow assimilation of remotely-sensed data sets and in-situ observations. HRAP-NLDAS centers on supporting NCEP and OHD operational land surface and hydrological modeling missions, as well as providing support for the NOAA Hydrology Test Bed, the NOAA Climate Test Bed, and NIDIS, with long-term retrospective (1979-present) and near real-time multi-model hydrometerological products over CONUS. New capabilities include the use of enhanced versions of the Noah and Sacramento Heat Transfer (SAC-HT) land models. As HRAP-NLDAS is developed under the NASA LIS framework, more land surface/hydrological models will be included in this system. This high resolution exercise will allow drought monitoring with spatial scales from state to sub-county levels.