SSEBop Evapotranspiration Products

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 the period 2000 to present. The SSEBop setup is Senay et al., 2011, 2013) combines ET fractions generated from remotely sensed MODIS thermal imagery, acquired every 8 days, with reference ET using a thermal index approach. ETa data and anomaly products (current vs. 2001 – 2015) are available at: http://earlywarning.usgs.gov/usewem/eta_energy.php. 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. based on the Simplified Surface Energy Balance (SSEB) approach ( with unique parameterization for operational applications. It 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.

Evaporative Demand Drought Index

The Evaporative Demand Drought Index (EDDI) exploits the strong physical relationship between evaporative demand (E0) and actual loss of water from the land surface through evapotranspiration. E0 is the “thirst of the atmosphere,” estimated by the amount of water that would evaporate from the soil and be transpired by plants if the soil were well watered. EDDI measures the signal of drought using information on the rapidly evolving (daily) conditions of the atmosphere to estimate their impact on land-surface moisture, and vice versa. EDDI’s effectiveness in reflecting the moisture conditions on the land surface is based on feedbacks between the atmosphere and land that are particularly strong during the warm season, when drought is of greatest concern. See the EDDI User Guide for more information.

The data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.

The drought category shown (D0, D1, D2, D3, D4) is a function of the depth of reference evapotranspiration accumulated over a given period of record (4-week, 8-week, 12-week) with respect to a climatology of 1980-2015. The drought categories are consistent with the US Drought Monitor's Percentile Ranking Scheme.

Evaporative Demand Drought Index

The Evaporative Demand Drought Index (EDDI) exploits the strong physical relationship between evaporative demand (E0) and actual loss of water from the land surface through evapotranspiration. E0 is the “thirst of the atmosphere,” estimated by the amount of water that would evaporate from the soil and be transpired by plants if the soil were well watered. EDDI measures the signal of drought using information on the rapidly evolving (daily) conditions of the atmosphere to estimate their impact on land-surface moisture, and vice versa. EDDI’s effectiveness in reflecting the moisture conditions on the land surface is based on feedbacks between the atmosphere and land that are particularly strong during the warm season, when drought is of greatest concern. See the EDDI User Guide for more information.

The data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.

The drought category shown (D0, D1, D2, D3, D4) is a function of the depth of reference evapotranspiration accumulated over a given period of record (4-week, 8-week, 12-week) with respect to a climatology of 1980-2015. The drought categories are consistent with the US Drought Monitor's Percentile Ranking Scheme.

Evaporative Demand Drought Index

The Evaporative Demand Drought Index (EDDI) exploits the strong physical relationship between evaporative demand (E0) and actual loss of water from the land surface through evapotranspiration. E0 is the “thirst of the atmosphere,” estimated by the amount of water that would evaporate from the soil and be transpired by plants if the soil were well watered. EDDI measures the signal of drought using information on the rapidly evolving (daily) conditions of the atmosphere to estimate their impact on land-surface moisture, and vice versa. EDDI’s effectiveness in reflecting the moisture conditions on the land surface is based on feedbacks between the atmosphere and land that are particularly strong during the warm season, when drought is of greatest concern. See the EDDI User Guide for more information.

The data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.

The drought category shown (D0, D1, D2, D3, D4) is a function of the depth of reference evapotranspiration accumulated over a given period of record (4-week, 8-week, 12-week) with respect to a climatology of 1980-2015. The drought categories are consistent with the US Drought Monitor's Percentile Ranking Scheme.

Evaporative Demand Drought Index

The Evaporative Demand Drought Index (EDDI) exploits the strong physical relationship between evaporative demand (E0) and actual loss of water from the land surface through evapotranspiration. E0 is the “thirst of the atmosphere,” estimated by the amount of water that would evaporate from the soil and be transpired by plants if the soil were well watered. EDDI measures the signal of drought using information on the rapidly evolving (daily) conditions of the atmosphere to estimate their impact on land-surface moisture, and vice versa. EDDI’s effectiveness in reflecting the moisture conditions on the land surface is based on feedbacks between the atmosphere and land that are particularly strong during the warm season, when drought is of greatest concern. See the EDDI User Guide for more information.

The data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.

The drought category shown (D0, D1, D2, D3, D4) is a function of the depth of reference evapotranspiration accumulated over a given period of record (4-week, 8-week, 12-week) with respect to a climatology of 1980-2015. The drought categories are consistent with the US Drought Monitor's Percentile Ranking Scheme.

Evaporative Demand Drought Index

The Evaporative Demand Drought Index (EDDI) exploits the strong physical relationship between evaporative demand (E0) and actual loss of water from the land surface through evapotranspiration. E0 is the “thirst of the atmosphere,” estimated by the amount of water that would evaporate from the soil and be transpired by plants if the soil were well watered. EDDI measures the signal of drought using information on the rapidly evolving (daily) conditions of the atmosphere to estimate their impact on land-surface moisture, and vice versa. EDDI’s effectiveness in reflecting the moisture conditions on the land surface is based on feedbacks between the atmosphere and land that are particularly strong during the warm season, when drought is of greatest concern. See the EDDI User Guide for more information.

The data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.

The drought category shown (D0, D1, D2, D3, D4) is a function of the depth of reference evapotranspiration accumulated over a given period of record (4-week, 8-week, 12-week) with respect to a climatology of 1980-2015. The drought categories are consistent with the US Drought Monitor's Percentile Ranking Scheme.

Evaporative Demand Drought Index

The Evaporative Demand Drought Index (EDDI) exploits the strong physical relationship between evaporative demand (E0) and actual loss of water from the land surface through evapotranspiration. E0 is the “thirst of the atmosphere,” estimated by the amount of water that would evaporate from the soil and be transpired by plants if the soil were well watered. EDDI measures the signal of drought using information on the rapidly evolving (daily) conditions of the atmosphere to estimate their impact on land-surface moisture, and vice versa. EDDI’s effectiveness in reflecting the moisture conditions on the land surface is based on feedbacks between the atmosphere and land that are particularly strong during the warm season, when drought is of greatest concern. See the EDDI User Guide for more information.

The data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.

The drought category shown (D0, D1, D2, D3, D4) is a function of the depth of reference evapotranspiration accumulated over a given period of record (4-week, 8-week, 12-week) with respect to a climatology of 1980-2015. The drought categories are consistent with the US Drought Monitor's Percentile Ranking Scheme.