La formulation de base du modèle PT-JPL dans le framework OpenET n'a pas changé par rapport à la formulation d'origine détaillée dans Fisher et al. (2008).
Toutefois, des améliorations et des mises à jour ont été apportées aux entrées du modèle et à l'intégration temporelle pour PT-JPL afin de tirer parti des ensembles de données météorologiques maillés contemporains, d'assurer la cohérence avec d'autres modèles, d'améliorer les estimations de l'évaporation en eau libre et de tenir compte de l'advection sur les zones de cultures et les zones humides dans les environnements semi-arides et arides. Ces modifications incluent l'utilisation de la réflectance de surface et du rayonnement thermique Landsat pour calculer les variables de rayonnement net, de rayonnement photosynthétiquement actif, de couvert végétal et d'humidité, ainsi que l'utilisation des données météorologiques NLDAS, Spatial CIMIS et gridMET pour estimer l'ensoleillement et l'ET de référence ASCE. Comme pour l'implémentation d'autres modèles OpenET, l'estimation de l'ET intégrée dans le temps quotidien et mensuel est basée sur la fraction de l'ET de référence ASCE. L'évaporation en eau libre est estimée selon une approche d'équilibre énergétique de surface d'Abdelrady et al. (2016), spécifique aux plans d'eau en tenant compte du flux thermique de l'eau plutôt que du flux thermique du sol.
Fisher, J.B., Tu, K.P. et Baldocchi, D.D., 2008. Estimations mondiales du flux d'eau entre la terre et l'atmosphère basées sur les données mensuelles AVHRR et ISLSCP-II, validées sur 16 sites FLUXNET. Remote Sensing of Environment, 112(3),
pp.901-919.
doi:10.1016/j.rse.2007.06.025
Abdelrady, A., Timmermans, J., Vekerdy, Z. et Salama, M., 2016.
Surface energy balance of fresh and saline waters: AquaSEBS. Remote
sensing, 8(7), p.583.
doi:10.3390/rs8070583
Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) La formulation de base du modèle PT-JPL dans le framework OpenET n'a pas changé par rapport à la formulation d'origine détaillée dans Fisher et al. (2008). Toutefois, des améliorations et des mises à jour ont été apportées aux entrées du modèle et à l'intégration temporelle pour PT-JPL afin de tirer parti des données météorologiques contemporaines sous forme de grille…
[null,null,[],[[["\u003cp\u003eThe OpenET PT-JPL dataset provides monthly evapotranspiration estimates for the contiguous United States (CONUS) from 2008 to 2023.\u003c/p\u003e\n"],["\u003cp\u003eIt is based on the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model, utilizing Landsat and gridMET data for improved accuracy.\u003c/p\u003e\n"],["\u003cp\u003eThe dataset is available at a 30-meter resolution and includes bands for evapotranspiration and the number of cloud-free observations used in the estimation.\u003c/p\u003e\n"],["\u003cp\u003eOpenET data is made available under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.\u003c/p\u003e\n"],["\u003cp\u003eThis dataset can be accessed and analyzed using Google Earth Engine.\u003c/p\u003e\n"]]],["The dataset, provided by OpenET, Inc., offers monthly evapotranspiration (ET) data from 1999-10-01 to 2023-12-01, calculated using the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model. This model uses Landsat data for variables and weather data to estimate ET, including adjustments for open water and advection. It outputs `et` values (mm) and a cloud-free `count`, with a 30-meter pixel size. The dataset is accessible through Google Earth Engine, which also provides an example code for annual evapotranspiration calculations.\n"],null,["# OpenET PT-JPL Monthly Evapotranspiration v2.0\n\nDataset Availability\n: 1999-10-01T00:00:00Z--2024-12-01T00:00:00Z\n\nDataset Provider\n:\n\n\n [OpenET, Inc.](https://openetdata.org/)\n\nCadence\n: 1 Month\n\nTags\n:\n[evapotranspiration](/earth-engine/datasets/tags/evapotranspiration) [gridmet-derived](/earth-engine/datasets/tags/gridmet-derived) [landsat-derived](/earth-engine/datasets/tags/landsat-derived) [monthly](/earth-engine/datasets/tags/monthly) [openet](/earth-engine/datasets/tags/openet) [water](/earth-engine/datasets/tags/water) [water-vapor](/earth-engine/datasets/tags/water-vapor) \n\n#### Description\n\nPriestley-Taylor Jet Propulsion Laboratory (PT-JPL)\n\nThe core formulation of the PT-JPL model within the OpenET framework has\nnot changed from the original formulation detailed in Fisher et al. (2008).\nHowever, enhancements and updates to model inputs and time integration for\nPT-JPL were made to take advantage of contemporary gridded weather datasets,\nprovide consistency with other models, improve open water evaporation\nestimates, and account for advection over crop and wetland areas in\nsemiarid and arid environments. These changes include the use of\nLandsat surface reflectance and thermal radiation for calculating net\nradiation, photosynthetically active radiation, plant canopy and moisture\nvariables, and use of NLDAS, Spatial CIMIS, and gridMET weather data for\nestimating insolation and ASCE reference ET. Similar to the implementation\nof other OpenET models, estimation of daily and monthly time integrated\nET is based on the fraction of ASCE reference ET. Open water evaporation\nis estimated following a surface energy balance approach of Abdelrady\net al. (2016) that is specific for water bodies by accounting for water\nheat flux as opposed to soil heat flux.\n\n[Additional information](https://openetdata.org/methodologies/)\n\n### Bands\n\n\n**Pixel Size**\n\n30 meters\n\n**Bands**\n\n| Name | Units | Pixel Size | Description |\n|---------|-------|------------|-----------------------------|\n| `et` | mm | meters | PT-JPL ET value |\n| `count` | count | meters | Number of cloud free values |\n\n### Image Properties\n\n**Image Properties**\n\n| Name | Type | Description |\n|-----------------------|--------|----------------------------------------------------------------------------------------------|\n| build_date | STRING | Date assets were built |\n| cloud_cover_max | DOUBLE | Maximum CLOUD_COVER_LAND percent value for Landsat images included in interpolation |\n| collections | STRING | List of Landsat collections for Landsat images included in the interpolation |\n| core_version | STRING | OpenET core library version |\n| end_date | STRING | End date of month |\n| et_reference_band | STRING | Band in et_reference_source that contains the daily reference ET data |\n| et_reference_resample | STRING | Spatial interpolation mode to resample daily reference ET data |\n| et_reference_source | STRING | Collection ID for the daily reference ET data |\n| interp_days | DOUBLE | Maximum number of days before and after each image date to include in interpolation |\n| interp_method | STRING | Method used to interpolate between Landsat model estimates |\n| interp_source_count | DOUBLE | Number of available images in the interpolation source image collection for the target month |\n| mgrs_tile | STRING | MGRS grid zone ID |\n| model_name | STRING | OpenET model name |\n| model_version | STRING | OpenET model version |\n| scale_factor_count | DOUBLE | Scaling factor that should be applied to the count band |\n| scale_factor_et | DOUBLE | Scaling factor that should be applied to the et band |\n| start_date | STRING | Start date of month |\n\n### Terms of Use\n\n**Terms of Use**\n\n[CC-BY-4.0](https://spdx.org/licenses/CC-BY-4.0.html)\n\n### Citations\n\nCitations:\n\n- Fisher, J.B., Tu, K.P. and Baldocchi, D.D., 2008. Global estimates of the\n land--atmosphere water flux based on monthly AVHRR and ISLSCP-II data,\n validated at 16 FLUXNET sites. Remote Sensing of Environment, 112(3),\n pp.901-919.\n [doi:10.1016/j.rse.2007.06.025](https://doi.org/10.1016/j.rse.2007.06.025)\n- Abdelrady, A., Timmermans, J., Vekerdy, Z. and Salama, M., 2016.\n Surface energy balance of fresh and saline waters: AquaSEBS. Remote\n sensing, 8(7), p.583.\n [doi:10.3390/rs8070583](https://doi.org/10.3390/rs8070583)\n\n### DOIs\n\n- \u003chttps://doi.org/10.1016/j.rse.2007.06.025\u003e\n\n### Explore with Earth Engine\n\n| **Important:** Earth Engine is a platform for petabyte-scale scientific analysis and visualization of geospatial datasets, both for public benefit and for business and government users. Earth Engine is free to use for research, education, and nonprofit use. To get started, please [register for Earth Engine access.](https://console.cloud.google.com/earth-engine)\n\n### Code Editor (JavaScript)\n\n```javascript\nvar dataset = ee.ImageCollection('OpenET/PTJPL/CONUS/GRIDMET/MONTHLY/v2_0')\n .filterDate('2020-01-01', '2021-01-01');\n\n// Compute the annual evapotranspiration (ET) as the sum of the monthly ET\n// images for the year.\nvar et = dataset.select('et').sum();\n\nvar visualization = {\n min: 0,\n max: 1400,\n palette: [\n '9e6212', 'ac7d1d', 'ba9829', 'c8b434', 'd6cf40', 'bed44b', '9fcb51',\n '80c256', '61b95c', '42b062', '45b677', '49bc8d', '4dc2a2', '51c8b8',\n '55cece', '4db4ba', '459aa7', '3d8094', '356681', '2d4c6e',\n ]\n};\n\nMap.setCenter(-100, 38, 5);\n\nMap.addLayer(et, visualization, 'OpenET PT-JPL Annual ET');\n```\n[Open in Code Editor](https://code.earthengine.google.com/?scriptPath=Examples:Datasets/OpenET/OpenET_PTJPL_CONUS_GRIDMET_MONTHLY_v2_0) \n[OpenET PT-JPL Monthly Evapotranspiration v2.0](/earth-engine/datasets/catalog/OpenET_PTJPL_CONUS_GRIDMET_MONTHLY_v2_0) \nPriestley-Taylor Jet Propulsion Laboratory (PT-JPL) The core formulation of the PT-JPL model within the OpenET framework has not changed from the original formulation detailed in Fisher et al. (2008). However, enhancements and updates to model inputs and time integration for PT-JPL were made to take advantage of contemporary gridded weather ... \nOpenET/PTJPL/CONUS/GRIDMET/MONTHLY/v2_0, evapotranspiration,gridmet-derived,landsat-derived,monthly,openet,water,water-vapor \n1999-10-01T00:00:00Z/2024-12-01T00:00:00Z \n25 -126 50 -66 \nGoogle Earth Engine \nhttps://developers.google.com/earth-engine/datasets\n\n- [https://doi.org/10.1016/j.rse.2007.06.025](https://doi.org/https://openetdata.org/)\n- [https://doi.org/10.1016/j.rse.2007.06.025](https://doi.org/https://developers.google.com/earth-engine/datasets/catalog/OpenET_PTJPL_CONUS_GRIDMET_MONTHLY_v2_0)"]]
