Actual ET (ETa) is produced using the operational Simplified Surface Energy Balance (SSEBop) model (Senay and others, 2013) for the period 2000 to present. The SSEBop setup is based on the Simplified Surface Energy Balance (SSEB) approach (Senay and others, 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 pre-defined, seasonally dynamic, boundary conditions that are unique to each pixel for the hot/dry and cold/wet reference points. Reference: Senay, G. B., Bohms, S., Singh, R. K., Gowda, P. H., Velpuri, N. M., Alemu, H., et al. (2013). Operational evapotranspirationmapping using remote sensing andweather datasets: A new parameterization for the SSEB approach. Journal of the American Water Resources Association, 1-2013;15, http://dx.doi.org/10.1111/jawr.12057. Reference: Velpuri, N. M., Senay, G. B., Singh, R. K., Bohms, S., and Verdin, J. P.: A comprehensive evaluation of two MODIS evapotranspiration products over the conterminous United States: Using point and gridded FLUXNET and water balance ET, Remote Sensing of Environment, 139, 35-49, http://dx.doi.org/10.1016/j.rse.2013.07.013, 2013.

These datasets are continuous parameter grids (CPG) of monthly mean evapotranspiration data for March through September, years 2000 through 2015, in the Pacific Northwest. Source evapotranspiration data was produced using the operational Simplified Surface Energy Balance (SSEBop) model.

This USGS data release is a result of using the OpenET Google Earth Engine (GEE) implementation of the USGS EROS Operational Simplified Surface Energy Balance (SSEBop, Senay and others, 2013; Senay and others, 2023) Evapotranspiration (ET) model to create Actual ET (ETa) estimates from remote sensing data at 30-m spatial resolution, supporting spatiotemporal ET coupling analysis with the USGS National Hydrologic Model (NHM; Regan and others, 2019). The results are Landsat-based monthly products generated from satellite imagery with <60% cloud cover and made available as a raster image collection from 2000-2020 for the conterminous United States (CONUS). SSEBop derivatives were used within the NHM to estimate consumptive use and effective precipitation on irrigated lands. Data products are spatially constrained and provided via modified Military Grid Reference System (MGRS) tiles which is based on the Universal Transverse Mercator (UTM) projection. Please refer to the Supplemental Information element of this metadata record for further information on this data.

Global alfalfa-reference potential evapotranspiration (ETr) is a key model parameter in actual evapotranspiration (ETa) modeling for worldwide applications. This dataset was constructed for use with the Operational Simplified Surface Energy Balance (SSEBop) model as a key driver of the final ETa magnitude. SSEBop is a parametric energy balance-based model that determines actual ET as the product of two independent estimates: 1) the SSEBop modeled ET fraction (ETf), an index nominally varying between 0 and 1 and derived from observed Landsat surface temperature using satellite psychrometry, and 2) the potential ET (maximum) under environmental conditions for an alfalfa crop (in millimeters). As SSEBop ETf can now be modeled for any Landsat scene across the globe, a suitable global ETr climatology dataset needed to be created. This global ETr data is a fusion of several different remote sensing and modeling products: 1981-2010 climatological normal (daily mean) ETr from Gridmet over the continental United States and 1981-2010 climatological normal MERRA-2 Fine Resolution ETr for all areas outside of the continental United States that has been scaled and corrected via terrestrial ecoregions from OneEarth and scaled using Worldclim Version 3 ETo (Abatzoglou 2013; Dinerstein et al., 2017; Hobbins et al., 2022; Zomer et al., 2022). The final mosaic has been smoothed and resampled to 1-km spatial resolution. The final dataset is a daily dataset of 366 GeoTIFF raster files for each day of the year including the leap day and representing a climatological normal (1981-2010) alfalfa-reference potential ET (ETr) for the entire global extent.

Global alfalfa-reference potential evapotranspiration (ETr) is a key model parameter in actual evapotranspiration (ETa) modeling for worldwide applications. This dataset was constructed for use with the Operational Simplified Surface Energy Balance (SSEBop) model as a key driver of the final ETa magnitude. SSEBop is a parametric energy balance-based model that determines actual ET as the product of two independent estimates: 1) the SSEBop modeled ET fraction (ETf), an index nominally varying between 0 and 1 and derived from observed Landsat surface temperature using satellite psychrometry, and 2) the potential ET (maximum) under environmental conditions for an alfalfa crop (in millimeters). As SSEBop ETf can now be modeled for any Landsat scene across the globe, a suitable global ETr climatology dataset needed to be created. This global ETr data is a fusion of several different remote sensing and modeling products: 1981-2010 climatological normal (daily mean) ETr from Gridmet over the continental United States and 1981-2010 climatological normal MERRA-2 Fine Resolution ETr for all areas outside of the continental United States that has been scaled and corrected via terrestrial ecoregions from OneEarth and scaled using Worldclim Version 3 ETo (Abatzoglou 2013; Dinerstein et al., 2017; Hobbins et al., 2022; Zomer et al., 2022). The final mosaic has been smoothed and resampled to 1-km spatial resolution. The final dataset is a daily dataset of 366 GeoTIFF raster files for each day of the year including the leap day and representing a climatological normal (1981-2010) alfalfa-reference potential ET (ETr) for the entire global extent.

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission measures the temperature of plants to better understand how much water plants need and how they respond to stress. ECOSTRESS is attached to the International Space Station (ISS) and collects data globally between 52 degrees N and 52 degrees S latitudes. The ECO2LSTE Version 1 data product provides atmospherically corrected land surface temperature and emissivity (LST&E) values derived from five thermal infrared (TIR) bands. The ECO2LSTE data product was derived using a physics-based Temperature and Emissivity Separation (TES) algorithm. The ECO2LSTE is provided as swath data and has a spatial resolution of 70 meters (m). The corresponding [ECO1BGEO](https://doi.org/10.5067/ECOSTRESS/ECO1BGEO.001) data product is required to georeference the ECO2LSTE data product.The ECO2LSTE Version 1 data product contains layers of LST, emissivity for bands 1 through 5, quality control for LST&E, LST error, emissivity error for bands 1 through 5, wideband emissivity, and Precipitable Water Vapor (PWV).Known Issues* Data acquisition gap: ECOSTRESS was launched on June 29, 2018, and moved to autonomous science operations on August 20, 2018, following a successful in-orbit checkout period. On September 29, 2018, ECOSTRESS experienced an anomaly with its primary mass storage unit (MSU). ECOSTRESS has a primary and secondary MSU (A and B). On December 5, 2018, the instrument was switched to the secondary MSU and science operations resumed. On March 14, 2019, the secondary MSU experienced a similar anomaly temporarily halting science acquisitions. On May 15, 2019, a new data acquisition approach was implemented and science acquisitions resumed. To optimize the new acquisition approach TIR bands 2, 4 and 5 are being downloaded. The data products are as previously, except the bands not downloaded contain fill values (L1 radiance and L2 emissivity). This approach was implemented from May 15, 2019, through April 28, 2023.* Data acquisition gap: From February 8 to February 16, 2020, an ECOSTRESS instrument issue resulted in a data anomaly that created striping in band 4 (10.5 micron). These data products have been reprocessed and are available for download. No ECOSTRESS data were acquired on February 17, 2020, due to the instrument being in SAFEHOLD. Data acquired following the anomaly have not been affected.* Data acquisition: ECOSTRESS has now successfully returned to 5-band mode after being in 3-band mode since 2019. This feature was successfully enabled following a Data Processing Unit firmware update (version 4.1) to the payload on April 28, 2023. To better balance contiguous science data scene variables, 3-band collection is currently being interleaved with 5-band acquisitions over the orbital day/night periods.

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission measures the temperature of plants to better understand how much water plants need and how they respond to stress. ECOSTRESS is attached to the International Space Station (ISS) and collects data over the conterminous United States (CONUS) as well as key biomes and agricultural zones around the world and selected FLUXNET (http://fluxnet.fluxdata.org/about/) validation sites. A map of the acquisition coverage can be found on the ECOSTRESS website (https://ecostress.jpl.nasa.gov/science). The NASA Jet Propulsion Laboratory (JPL) ECO3ETALEXI Version 1 data product provides estimates of daily evapotranspiration (ET) using the ECOSTRESS Level 2 (L2) land surface temperature and emissivity (LST&E) product, along with ancillary meteorological data and remotely sensed vegetation cover information. The ECO3ETALEXI data product is derived using a physics-based surface energy balance (SEB) algorithm, the Atmosphere Land Exchange Inverse (ALEXI) Disaggregation algorithm (DisALEXI). Described in the Algorithm Theoretical Basis Document (ATBD) (https://lpdaac.usgs.gov/documents/1000/ECO3ETALEXI_ATBD_V1.pdf), DisALEXI is based on spatial disaggregation of regional-scale fluxes from the ALEXI SEB model. There are many approaches for spatially mapping ET; however, SEB methods are favored for remote sensing retrievals based on land-surface temperature. ALEXI was initially developed for managed landscapes and has now been evaluated in comparison with micrometeorological flux tower observations over crop, forest, grassland, wetland, and semiarid desert sites. Applications include crop water use, crop phenology monitoring, and drought early warning or water stress detection. ECO3ETALEXI is available for CONUS at 70-meter (m) pixel resolution. The ECO3ETALEXI Version 1 data product contains layers of daily ET, ET uncertainty, and associated quality flags. A low-resolution browse is also available showing daily ET as a stretched image with a color ramp in JPEG format.

The dataset contains daily grass-reference evapotranspiration (ETo) maps stored as ASCII files. ETo at a 2 km spatial resolution are calculated statewide using the American Society of Civil Engineers version of the Penman-Monteith equation (ASCE-PM). Required input parameters for the ASCE-PM ETo equation are solar radiation, air temperature, relative humidity, and wind speed at two meters height. These parameters are estimated for each 2 km pixel using various methods. Daily solar radiation is generated from the visible band of the National Oceanic and Atmospheric Administration's (NOAA) Geostationary Operational Environmental Satellite (GOES) using the Heliosat-II model. This model is designed to convert images acquired by the Meteosat satellite into maps of global (direct plus diffused) irradiation received at ground level.

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission measures the temperature of plants to better understand how much water plants need and how they respond to stress. ECOSTRESS is attached to the International Space Station (ISS) and collects data globally between 52 degrees N and 52 degrees S latitudes. The ECOSTRESS Gridded Evapotranspiration Instantaneous and Daytime L3 Global 70 m (ECO_L3G_JET) Version 2 data product provides instantaneous canopy transpiration, leaf surface evaporation, and soil moisture evaporation using the Priestley-Taylor formula. This data product is mosaicked from the L3 tiled JET ([ECO_L3T_JET](https://doi.org/10.5067/ECOSTRESS/ECO_L3T_JET.002)) product, projected to a globally snapped 0.0006° grid, and has a spatial resolution of 70 meters (m).The ECO_L3G_JET Version 2 data product contains 12 layers distributed in an HDF5 format file including ETdaily, ETinstUncertainty, PTJPLSMinst, STICinst, MOD16inst, BESSinst, STICcanopy, PTJPLSMcanopy, PTJPLSMinterception, PTJPLSMsoil, cloud mask, and water mask.Improvements/Changes from Previous Versions* This product utilizes a modified version of the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model from the ECOSTRESS Evapotranspiration PT-JPL Daily L3 Global 70 m ([ECO3ETPTJPL](https://doi.org/10.5067/ECOSTRESS/ECO3ETPTJPL.001)) Version 1 data product which incorporates soil moisture as an added constraint (PT-JPL-SM). In addition to PT-JPL-SM, this data product includes the outputs from other models not included in ECO3ETPTJPL v001, details on what is included can be found in Section 5.4 of the User Guide.Known Issues* Data acquisition gap: ECOSTRESS was launched on June 29, 2018, and moved to autonomous science operations on August 20, 2018, following a successful in-orbit checkout period. On September 29, 2018, ECOSTRESS experienced an anomaly with its primary mass storage unit (MSU). ECOSTRESS has a primary and secondary MSU (A and B). On December 5, 2018, the instrument was switched to the secondary MSU and science operations resumed. On March 14, 2019, the secondary MSU experienced a similar anomaly, temporarily halting science acquisitions. On May 15, 2019, a new data acquisition approach was implemented, and science acquisitions resumed. To optimize the new acquisition approach TIR bands 2, 4, and 5 are being downloaded. The data products are as previously, except the bands not downloaded contain fill values (L1 radiance and L2 emissivity). This approach was implemented from May 15, 2019, through April 28, 2023.* Data acquisition gap: From February 8 to February 16, 2020, an ECOSTRESS instrument issue resulted in a data anomaly that created striping in band 4 (10.5 micron). These data products have been reprocessed and are available for download. No ECOSTRESS data were acquired on February 17, 2020, due to the instrument being in SAFEHOLD. Data acquired following the anomaly have not been affected.* Data acquisition: ECOSTRESS has now successfully returned to 5-band mode after being in 3-band mode since 2019. This feature was successfully enabled following a Data Processing Unit firmware update (version 4.1) to the payload on April 28, 2023. To better balance contiguous science data scene variables, 3-band collection is currently being interleaved with 5-band acquisitions over the orbital day/night periods.* Solar Array Obstruction: Some ECOSTRESS scenes may be affected by solar array obstructions from the International Space Station (ISS), potentially impacting data quality of obstructed pixels. The ‘FieldOfViewObstruction’ metadata field is included in all Version 2 products to indicate possible obstructions: * Before October 24, 2024 (orbits prior to 35724): The field is present but was not populated and does not reliably identify affected scenes. * On or after October 24, 2024 (starting with orbit 35724): The field is populated and generally accurate, except for late December 2024, when a

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission measures the temperature of plants to better understand how much water plants need and how they respond to stress. ECOSTRESS is attached to the International Space Station (ISS) and collects data globally between 52 degrees N and 52 degrees S latitudes. The United States Department of Agriculture (USDA) ECO3ETALEXIU Version 1 data product provides estimates of daily evapotranspiration (ET) using the ECOSTRESS Level 2 (L2) land surface temperature and emissivity (LST&E) product, along with ancillary meteorological data and remotely sensed vegetation cover information. The ECO3ETALEXIU data product is derived using a physics-based surface energy balance (SEB) algorithm, the Atmosphere Land Exchange Inverse (ALEXI) Disaggregation algorithm (disALEXI). Described in the Algorithm Theoretical Basis Document (ATBD), disALEXI is based on spatial disaggregation of regional-scale fluxes from the ALEXI SEB model. Many approaches exist for mapping ET spatially; however, SEB methods are favored for remote sensing retrievals based on land-surface temperature. ALEXI was initially developed for managed landscapes. Applications include crop water use, crop phenology monitoring, and drought early warning or water stress detection. The output ET is generated on a UTM grid at a spatial resolution of 30 meters.The ECO3ETALEXIU Version 1 data product contains variables of daily ET, ET uncertainty, and associated quality flags. A low-resolution browse is also available showing daily ET as a stretched image with a color ramp in JPEG format.Known Issues* Data acquisition gaps: ECOSTRESS was launched on June 29, 2018, and moved to autonomous science operations on August 20, 2018, following a successful in-orbit checkout period. On September 29, 2018, ECOSTRESS experienced an anomaly with its primary mass storage unit (MSU). ECOSTRESS has a primary and secondary MSU (A and B). On December 5, 2018, the instrument was switched to the secondary MSU and science operations resumed. On March 14, 2019, the secondary MSU experienced a similar anomaly temporarily halting science acquisitions. On May 15, 2019, a new data acquisition approach was implemented and science acquisitions resumed. To optimize the new acquisition approach TIR bands 2, 4 and 5 are being downloaded. The data products are as previously, except the bands not downloaded contain fill values (L1 radiance and L2 emissivity). This approach was implemented from May 15, 2019, through April 28, 2023.* Data acquisition gap: From February 8 to February 16, 2020, an ECOSTRESS instrument issue resulted in a data anomaly that created striping in band 4 (10.5 micron). These data products have been reprocessed and are available for download. No ECOSTRESS data were acquired on February 17, 2020, due to the instrument being in SAFEHOLD. Data acquired following the anomaly have not been affected.* Data acquisition: ECOSTRESS has now successfully returned to 5-band mode after being in 3-band mode since 2019. This feature was successfully enabled following a Data Processing Unit firmware update (version 4.1) to the payload on April 28, 2023. To better balance contiguous science data scene variables, 3-band collection is currently being interleaved with 5-band acquisitions over the orbital day/night periods.