Integrating a Real-time Green Vegetation Fraction (GVF) Product into the Land Information System (LIS)

Land surface modeling is an important input of meteorological models in order for them to correctly initialize parameters such as soil temperature and moisture. NASA's Land Information System (LIS) is a framework encompassing many different land surface models (LSM), and is currently run at the Air Force Weather Agency (AFWA) using the NOAH LSM. One input to NOAH is the greenness of the land, or green vegetation fraction (GVF), which has impacts on parameters such as surface heat fluxes and albedo. Currently, LIS at AFWA reads in GVF from static climatological files, using a 5 year monthly AVHRR-based (Advanced Very High Resolution Radiometer) climatology, interpolated to the current date. However, GVF can have variations from year to year, mainly based on how wet or dry the area is that year. An algorithm to compute a real-time GVF based on the Normalized Differential Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS), developed by UCAR is being integrated at AFWA. A 14-day average of this GVF, updated daily, is directly inserted into LIS in place of the climatological data. Resulting changes in parameters, such as heat fluxes and albedo, are analyzed when comparing LIS output using the real-time greenness to LIS output using the climatological greenness.