Operational Transition of Soil Moisture and Snow Data Assimilation in the North American Land Data Assimilation System (NLDAS)

The North American Land Data Assimilation System (NLDAS) has a long successful history of producing land-surface model (LSM) products, such as soil moisture, snow cover, and runoff/streamflow. On 5 August 2014, the NLDAS system transitioned into operations at NCEP. Real-time NLDAS products are used for drought monitoring and as initial conditions for a drought forecast system. However, our previous MAPP project showed that the operational NLDAS could be improved if snow and soil moisture were assimilated into the real-time system. Furthermore, the streamflow routing scheme within NLDAS does not include information on either river stage or floodplains. We believe that assimilating operational satellite products into upgraded NLDAS LSMs combined with an enhanced streamflow routing scheme will produce improved data products to better represent evolving conditions for drought monitoring and water resource management. Further, the use of a computationally parallel modeling environment (vs. the serial operational NLDAS) is critical if these anticipated updates are to be realized.

The proposed work will include the following three elements: 1) Upgrading the real-time operational NLDAS data production and drought monitoring system using the latest Land Information System (LIS) software architecture, LSM model upgrades, and soil moisture and snow data assimilation capabilities; 2) Adding the Hydrological Modeling and Analysis Platform (HyMAP) into the operational NLDAS to enable river stage and floodplain analysis as well as reservoir routing; and 3) Performing a thorough evaluation of the current and future operational NLDAS systems using the Land Verification Toolkit (LVT) and NLDAS testbed evaluation/validation tools. This effort will transition existing LSM model upgrades and data assimilation capabilities developed through a previous MAPP project, and will enable a parallel, scalable environment for NLDAS. The work will involve assimilating NESDIS’ Soil Moisture Operational Products System (SMOPS) soil moisture, Interactive Multisensor Snow and Ice Mapping System (IMS) snow-covered area, and Air Force SNODEP snow depth products into the operational NLDAS system. The result of this research to operations transition will be better diagnosis of drought events as well as improvement of initial land conditions for the NLDAS quasi-operational seasonal hydrological (drought-focused) forecast system and the operational North American Model (NAM) short-term weather forecast system.