HR: 0800h
AN: H41A-0391    [Abstracts]
TI: Global Daily Reference ET Modeling and Evaluation
AU: Senay, G B
EM: senay@usgs.gov
AF: SAIC-USGS/EROS, 47914 252nd st, Sioux Falls, SD 57198 United States
AU: * Verdin, J P
EM: verdin@usgs.gov
AF: USGS/EROS, 47914 252nd st, Sioux Falls, SD 57198 United States
AU: Lietzow, R
EM: lietzow@usgs.gov
AF: USGS/EROS, 47914 252nd st, Sioux Falls, SD 57198 United States
AB: Accurate and reliable Evapotranspiration (ET) data sets are crucial in regional water and energy balance studies. Due to the complex instrumentation requirements, actual ET values are generally estimated from reference ET values by adjustment factors using coefficients for water stress and vegetation conditions, commonly referred to as crop coefficients. Until recently, the modeling of reference ET has been solely based on important weather variables collected from weather stations that are generally located on selected agro-climatic locations. Since 2000, NOAA's Global Data Assimilation System (GDAS) has been producing 6-hourly climate parameter data sets of the input meteorological variables used to calculate daily reference ET for the whole globe at 1 degree spatial resolution. USGS at the Center for Earth Resources Observation and Science (EROS) has been producing daily reference ET since 2000 and the results have been used for a variety of models for drought and stream flow monitoring all over the world in an operational basis. With the increasing availability of station-based reference ET estimates over the internet, we evaluated the GDAS-based reference ET estimates using data from the California Irrigation Management Information System (CIMIS). Daily CMIS reference ET estimates from over 120 stations were compared with GDAS-based reference ET at different spatial and temporal scales using the 2004 data. Despite the large difference in spatial scale (point vs ~100 km grid) between the two data sets, the correlations between station-based ET and GDAS-ET were very high, exceeding 0.90 on a daily-basis to more than 0.98 on time scales of over 10 days. The effect of elevation in the reference ET estimation at a coarse spatial scale was also investigated. Both the temporal and spatial correspondences in trend/pattern and magnitudes between the two data sets were satisfactory, suggesting the reliability of using GDAS parameter based reference ET for regional water and energy balance studies in many parts of the world.
DE: 1818 Evapotranspiration
DE: 1819 Geographic Information Systems (GIS)
DE: 1840 Hydrometeorology
DE: 1847 Modeling
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: Fall Meeting 2005