SSEBop Evapotranspiration Anomaly Products|
(Version 2.0, April 2013)
Evapotranspiration (ET) is the combination of transpiration from vegetation and evaporation
from soil. Actual ET (ETa) is produced using the operational Simplified Surface Energy Balance
(SSEBop) model (Senay et al., 2013) for the period 2000 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 8 days, with reference ET using a
thermal index approach. The unique feature of the SSEBop parameterization is that it uses predefined,
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.
ETa anomaly products (current vs. 2001 2010) are available at the following:
http://earlywarning.usgs.gov/fews/africa/index.php. 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 precipitation.
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 8-day periods and grouped by major growing seasons:
- September June Southern Africa growing season
- September January East Africa growing season (short rains)
- May December East Africa (long rains, Ethiopia) and West Africa growing season
- January July East Africa growing season (long rains)
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 212213: 198212.
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. Singh, P.A. Gowda, N.M. Velpuri, H. Alemu and J.P. Verdin, 2013. Operational evapotranspiration mapping using remote sensing and weather datasets: A new parameterization for the SSEB approach. Journal of American Water Resources Research. In Press.