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Near Real-time Experiments
Research Approach


The evapotranspiration is estimated using remote sensing data to the great extent possible. Spatial mapping of energy partitioning is calculated from satellite remote sensing data. It is used for estimating evaporation fraction (EF), expressed as a ratio of actual evapotranspiration (ET) to the available energy (sum of ET and sensible heat flux), from satellite data. The landscape is characterized as a mixture of bare soil and vegetation and thus EF is estimated as a mixture of EF of bare soil and EF of vegetation.

The instantaneous EF is estimated at the moment when the remote sensing data is available. We assume the EF is a constant during daytime that is truth during most daytime in many cases. Therefore the daily average ET is calculated using the instantaneous EF and average available energy.


The approach uses the most recent MODIS data. The data include MOD12Q1 (Land Cover Type Yearly L3 Global 1km), MOD09GQ (Surface Reflectance Daily L2G Global 250m), MOD11A1 (Land Surface Temperature/Emissivity Daily L3 Global 1km), MOD13Q1 (Vegetation Indices 16-Day L3 Global 250m), and MCD43A3 (Albedo 16-Day L3 Global 500m) etc. Surface radiation components are obtained from GCIP SRB (Surface Radiation Budget Data 0.5 degree). The algorithm of the approach is detailed at Research/Education page.

The approach is performed at the domain of (124.5W,119.5W,37.5N,44N). The lag time for these plots is currently about 4 days.The lag time depends on the MODIS data availability.

DEM IGBP Landcover Landcover Class

Update Information

The remote sensing data update information for the last update time is summarized below.
LST_Day_1km 2010 8 8
LST_Night_1km 2010 8 8
Day_view_time 2010 8 8
Night_view_time 2010 8 8
Emis_31 2010 8 8
Emis_32 2010 8 8
sur_refl_b01_1 2010 9 2
sur_refl_b02_1 2010 9 2
state_1km_1 2010 9 2
Albedo_BSA_shortwave 2010 8 5
Albedo_WSA_shortwave 2010 8 5
The latest update (derived parameters):
NDVI_day_250_ref 2010 9 2

The last update time is Thu Sep 9 08:40:02 PDT 2010. The last estimation date is Wed Sep 8 2010.

   September 2010
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Tang, Q., S. Peterson, R. Cuenca, Y. Hagimoto and D. P. Lettenmaier, 2009. Satellite-based near real-time estimation of irrigated crop water consumption. Journal of Geophysical Research, (in press).
Nishida, K., R. R. Nemani, S. W. Running, and J. M. Glassy (2003), An operational remote sensing algorithm of land surface evaporation, J. Geophys. Res., 108(D9), 4270, doi:10.1029/2002JD002062.
Cleugh, Helen A., Leuning, R., Mu, Q., Running, S.W. (2007). Regional evaporation estimates from flux tower and MODIS satellite data. Remote Sensing of the Environment, 106(3), 285-304.
Jiang, L., and S. Islam (2001), Estimation of surface evaporation map over southern Great Plains using remote sensing data, Water Resour. Res., 37(2), 329-340.