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Monthly Evapotranspiration (ET) Anomaly

Continental Africa

Monthly Evapotranspiration (ET) Anomaly
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Monthly Period



Available Tools

GeoCLIM

The GeoCLIM is a spatial analysis tool designed for climatological analysis of historical rainfall and temperature data. The GeoCLIM provides non-scientists with an array of accessible analysis tools for climate-smart agricultural development. These user friendly tools can be used to obtain and analyze climate data, blend station data with satellite data to create more accurate datasets, analyze seasonal trends and/or historical climate data, create visual representations of climate data, create scripts (batch files) to quickly and efficiently analyze similar “batches” of climate data, view and/or edit shapefiles and raster files, and extract statistics from raster datasets to create time series.

Product Documentation

SSEBop Evapotranspiration Products

(Version 4.0, June 2017)

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., 2012) for 2003 to present. The SSEBop setup is based on the Simplified Surface Energy Balance (SSEB) approach (Senay et al., 2011, 2013) with unique parameterization for operational applications. It combines ET fractions generated from remotely sensed MODIS thermal imagery, acquired every 10 days, 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.
ETa data and anomaly products (current vs. 2003 – 2015) are available at: https://earlywarning.usgs.gov/fews.

The actual ET data unit is millimeters (mm) and the associated color ramp (see Figure 1a.) is available for download as a .style file for ArcGIS and as txt file with RGB color codes. The SSEBop_symbology folder includes instructions on how to add the color ramp in ArcMap and further suggestions on the data visualization.

The anomalies are the ratio of ETa and the corresponding median ETa, expressed as a percent value and have the color ramp (see Figure 1b.) attached. The color ramp, txt file with RGB color codes, and colormap file (.clr) are available in the SSEBop_symbology folder.

Figure 1a.

Figure 1b.

Listed below are all ET products offered:

Yearly ET products:
ET data products as graphics (.png and .pdf), as well as .tif file. The associated color ramp is available as download on the website.
ET anomaly products for every year as graphics (.png and .pdf), as well as .tif including the color ramp.

Monthly ET products:
ET data products for every month in a year as graphics (.png and .pdf), as well as .tif file. The associated color ramp is available as download on the website.
ET anomaly products for every month in a year as graphics (.png and .pdf), as well as .tif file including the color ramp.

Dekadal (10 day) products:
ET data products for every dekad in a year as graphics (.png and .pdf), as well as .tif file. The associated color ramp is available as download on the website.
ET anomaly products for every dekad in a year as graphics (.png and .pdf), as well as .tif file including the color ramp.

Cumulative ET anomaly products:
ET anomaly products are cumulative in intervals of dekads and grouped by the region's main growing season(s).
ET anomaly products for every dekad in a year as graphics (.png and .pdf), as well as .tif file including the color ramp.

References:

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 212–213: 198–212.

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.