Real-Time Land Information System:
SPoRT has developed a real-time configuration of the NASA Land Information System (LIS; Kumar et al. 2006, 2007) that runs over much of the central and eastern United States at 3-km grid spacing, with a 3-km resolution nested grid centered on Alabama. The real-time LIS has been running since Summer 2010 to support local modeling, as well as provide forecast offices with experimental land surface fields that can aid short-term forecasting and situational awareness. Recent versions of the Weather Research and Forecasting (WRF) Environmental Modeling System (EMS; Rozumalski 2007) contain an option to use LIS data for initializing land surface variables in local model runs. The LIS/Noah output are part of the SPoRT Local Data Manager data stream such that partner offices can acquire the data and display them in their decision support system.
The real-time LIS consists of a continuous integration of the Noah land surface model, which is same land surface model used in the operational National Centers for Environmental Prediction (NCEP) North American Mesoscale model. Prior to real-time implementation, the LIS/Noah run was initialized with a uniform first-guess soil moisture and soil temperature, and integrated in an offline mode for several years. In an offline mode, the land surface model is run apart from a numerical weather prediction model, with input variables (i.e. forcing) provided by atmospheric analyses. In this instance, a long-term "spin-up" integration of LIS/Noah is driven by input forcing from the NCEP Global Data Assimilation System (GDAS; Derber et al. 1991) analyses, North American Land Data Assimilation System (NLDAS; Cosgrove et al. 2003a, b) analyses, and hourly precipitation estimates from the NCEP Stage IV product (Lin and Mitchell 2005; Lin et al. 2005). The several-year integration is required to remove any memory of the first-guess initialization and ensure that the soil variables have reached an equilibrium state with the atmospheric input forcing. Starting in Summer 2010, this long-term LIS/Noah integration has been continually re-started every 6 hours in a real-time capacity to provide (1) land surface initialization variables at high resolution for local numerical weather prediction models, and (2) high-resolution depictions of the land surface that can aid short-term forecasting and situational awareness at NWS weather forecast offices.
To ensure data availability in real time applications, short-term forecasts up to 15 hours from the NCEP Global Forecast System (GFS) model are used in each 6-hourly LIS/Noah cycle, thus providing a small forecast component to the real-time LIS. Output forced by the GFS forecasts is over-written in subsequent cycles as atmospheric analyses become available, ensuring a realistic land surface solution based on analyses. Output is written into gridded binary (GRIB) format, thus enabling an easy incorporation into the WRF EMS and display in AWIPS/AWIPS II. Beginning in April 2011, the real-time LIS began ingesting SPoRT's daily 1-km resolution MODIS Greenness Vegetation Fraction (GVF) data (Case et al. 2011a) in place of the 0.144° resolution NCEP GVF climatology for improved representation of vegetation coverage in the LIS/Noah integration. Figure 1 shows the geographical coverage of the regional and Alabama-centric 3-km domains.