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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Research Project #418414


Location: Hydrology and Remote Sensing Laboratory

2010 Annual Report

1a. Objectives (from AD-416)
To bring an existing drought and ET remote sensing model (ALEXI) into operational function within NOAA-NESDIS, and to deliver products to NAA-CPC, the National Drought Mitigation Center (NDMC), and the NIDIS Drought Portal for use in operational drought monitoring within the U.S. and North America.

1b. Approach (from AD-416)
The ALEXI model automated infrastructure will be connected to standard NOAA input products and conformed to run on a computing platform at NESDIS. An archive of model output will be generated for 2000-present over the contiguous U.S., and for 2007-present for a domain covering North America. Monthly anomalies in an Evaporative Stress Index (ESI), ET and soil moisture from the model will be compared with standard drought indices, with soil moisture observations, and with known drought events to ascertain robustness and model sensitivity. After ESI has been evaluated, it will be used to verify drought forecasts generated by CPC for the North American Drought Briefing. ALEXI drought products will be delivered in real-time to CPC and to NDMC for operational monitoring, and they will also be distributed through the U.S. Drought Portal.

3. Progress Report
The objective of this project is to produce satellite-based maps of evapotranspiration (ET) and soil moisture (SM)-related drought indices over North America in direct support of the NCEP/CPC North American Drought Briefing (NADB) and the National Integrated Drought Information System (NIDIS). Products will be delivered in near real-time directly to NCEP/CPC and distributed publically through the NIDIS U.S. Drought Portal. The remote sensing products will be generated by a regional-scale Atmosphere-Land Exchange Inverse (ALEXI) model, which diagnoses the surface energy balance using a time-differential land-surface temperature rise signal derived from GOES thermal imagery. The ALEXI-based Evaporative Stress Index (ESI), representing standardized anomalies in the ratio of actual to potential ET, shows good spatiotemporal correspondence with standard precipitation-based drought indices. In this work, we are developing a suite of ALEXI drought products on a 1/8o grid over the contiguous U.S. (CONUS), Canada, and Mexico, with the intent of transition to operations within NESDIS/NCEP by the project’s end. In Year 1 of this project, the primary implementation tasks were to 1) port the ALEXI processing infrastructure, currently running at University of Alabama-Huntsville (ALEXI-UAH), to machines at NESDIS, integrating standard NOAA input products (ALEXI-NOAA); and 2) conduct an intercomparison of the existing 10-year ALEXI-UAH ESI archive with standard drought indices used in the U.S. Drought Monitor (USDM) and NADB, and with the USDM itself. For task 1: Hourly skin temperature and insolation for much of the archive period have been obtained from the NESDIS GOES Surface and Insolation Product (GSIP) and collocated to the North American ALEXI domain. Meteorological inputs to ALEXI are being extracted from the Regional Climate Data Assimilation System (R-CDAS) – the real-time continuation of the North American Regional Reanalysis (NARR) performed by the NCEP Environmental Modeling Center (EMC). NARR fields have been extracted and archived for much of the archive period and a new pre-processing system has been developed to ingest NARR meteorological fields needed by ALEXI. For task 2: An intercomparison was conducted between the ESI, standard precipitation-based indices (SPI, PDSI, PHDI, Z, PMDI) and drought classifications reported in the U.S. Drought Monitor during 2000-2009. Spatial distributions in ESI were found to correlate well with patterns in the precipitation-based indices, responding to rainfall events at monthly timesteps. The intercomparison is being extended to include the Vegetation Health Index and other precipitation products used in the NADB.

4. Accomplishments