SSEBop Evapotranspiration Anomaly Products|
Evapotranspiration (ET) is the combination of transpiration from vegetation (through the
root system) and direct evaporation from soil-vegetation-water surfaces. Actual ET (ETa) is
produced using the Operational Simplified Surface Energy Balance (SSEBop) model (Senay
et al., 2013) for the period 2003 to present. The SSEBop setup is based on the Simplified
Surface Energy Balance (SSEB) approach (Senay et al., 2007, 2011) with unique
parameterization for operational applications. It combines ET fractions generated from
remotely sensed MODIS thermal imagery, acquired every dekad (10-day), with reference
ET using a thermal index approach. The unique feature of the SSEBop parameterization is
that it uses pre-defined, seasonally dynamic, boundary conditions that are unique to each
pixel for the “hot/dry” and “cold/wet” reference points. The original formulation of SSEB is
based on the hot and cold pixel principles of SEBAL (Bastiaanssen et al., 1998) and METRIC
(Allen et al., 2007) models. The SSEBop model has been validated comprehensively in the
conterminous U.S. using eddy covariance flux tower ET, basin water balance ET and in
comparison with MOD16 ET by Velpuri et al. (2013) and also against lysimeters by Senay et
ETa anomaly products (current vs. 2003 - 13) are available at the following: http://earlywarning.usgs.gov/fews/global/. The anomalies are the ratio of ETa and the
corresponding median ETa, expressed as a percent value. Arid regions with little or no
vegetation (maximum NDVI < 0.25) are replaced with precipitation values for the
corresponding period. In arid climates the magnitude of actual ET can be approximated by
Listed below are all ETa anomaly products offered:
Monthly ETa products:
ETa anomaly products for every month in a year.
Cumulative ETa anomaly products:
ETa anomaly products are cumulative in intervals of dekads and grouped by the region's main growing
Allen, R.G., Tasumi, M., Trezza, R., 2007. Satellite-based energy balance for mapping
evapotranspiration with internalized calibration (METRIC) – Model. ASCE J. Irrigation
and Drainage Engineering 133, 380-394.
Bastiaanssen, W.G.M., M. Menenti, R.A. Feddes, and A. A. M. Holtslag, 1998. The surface
energy balance algorithm for land (SEBAL): Part 1 formulation. Journal of Hydrology
Senay, G.B., M. Budde, J.P. Verdin, and A.M. Melesse, 2007. A coupled remote sensing and
simplified surface energy balance approach to estimate actual evapotranspiration from
irrigated fields. Special issue: Remote sensing of natural resources and the environment.
SENSORS, 1, 979-1000.
Senay, G.B., M. Budde, J.P. Verdin, 2011. Enhancing the Simplified Surface Energy Balance
(SSEB) approach for estimating landscape ET: Validation with the METRIC model.
Agricultural Water Management, 98: 606-618.
Senay, G.B., S. Bohms, R.K. Singh, P.H. Gowda, N.M. Velpuri, H.Alemu, and J.P. Verdin,
2013. Operational evapotranspirationmapping using remote sensing andweather datasets:
A new parameterization for the SSEB approach. Journal of the American Water
Resources Association, 1–15, http://dx.doi.org/10.1111/jawr.12057.
Senay, G.B., P.H. Gowda, S. Bohms, T.A. Howell, M. Friedrichs, T.H. Marek, and J. P. Verdin,
2014. Evaluating the SSEBop approach for evapotranspiration mapping with landsat data
using lysimetric observations in the semi-arid Texas High Plains Hydrol. Earth Syst. Sci.
Discuss., 11, 723–756, 2014. www.hydrol-earth-syst-sci-discuss.net/11/723/2014/
Velpuri, N.M., G.B. Senay, R.K. Singh, S. Bohms, and J.P. Verdin, 2013. A comprehensive
evaluation of two MODIS evapotranspiration products over the conterminous United
States:Using point and gridded FLUXNET and water balance ET, Remote Sens.
Environ., 139, 35–49, doi:10.1016/j.rse.2013.07.013.