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image of DAYMET data over North America
image of DAYMET data over North America
image of DAYMET data over North America

Daymet

Daymet uses statistical modeling techniques to provide long-term, continuous, gridded estimates of daily weather and climatology variables from ground-based observations. Daymet weather variables include daily minimum and maximum temperature, precipitation, vapor pressure, shortwave radiation, snow water equivalent, and day length over continental North America, Hawaii, and Puerto Rico.

Daymet is a research product of the Environmental Sciences Division at Oak Ridge National Laboratory, Oak Ridge, TN. Daymet is supported by NASA through the Earth Science Data and Information System (ESDIS) Project and the agency's Terrestrial Ecology Program. The continued development of the Daymet algorithm and processing is also supported by the Office of Biological and Environmental Research within the U.S. Department of Energy's Office of Science.

Six Daymet data products are available. Weather variables include daily minimum and maximum temperature, precipitation, vapor pressure, shortwave radiation, snow water equivalent, and day length produced on a 1 km x 1 km gridded surface over continental North America and Hawaii from 1980 and over Puerto Rico from 1950 through the end of the most recent full calendar year.

DatasetPublishedLink to User GuideVisualize and subset data using the Spatial Data Access Tool (SDAT)Visualize and subset data using the Thematic Real-time Environmental Distributed Data Services (THREDDS)

Daymet Version 4 Monthly Latency: Daily Surface Weather Data

 
May 28, 2021User Guide  
Annual Climate Summaries on a 1-km Grid for North America, Version 4 R1November 1, 2022User GuideSDAT LinkTHREDDS Link
Daily Surface Weather Data on a 1-km Grid for North America, Version 4 R1November 1, 2022User Guide THREDDS Link
Monthly Climate Summaries on a 1-km Grid for North America, Version 4 R1November 1, 2022User GuideSDAT LinkTHREDDS Link
Station-Level Inputs and Cross-Validation for North America, Version 4 R1November 1, 2022User Guide THREDDS Link

Sub-daily Climate Forcings for Puerto Rico

 
August 15, 2023User Guide  

Daymet is a model algorithm. Required model inputs include a digital elevation model, derived horizon files, a land water mask, and observations of daily maximum temperature, minimum temperature, and precipitation from ground-based meteorological stations. One file per year for each year of station data is assembled and input into the Daymet model algorithm.

Spatial Resolution: 1 km x 1 km

Temporal Resolution: Daily

Years Available:

  • North America, Hawaii: 1980 to present
  • Puerto Rico: 1950 to present (Puerto Rico data prior to 1980 are not available through the Single Pixel Extraction Tool)

The North American Daymet projection system and parameters:

  • Projection System: Lambert Conformal Conic
  • Projection Units: meters
  • Datum (spheroid): WGS_84
  • 1st Standard Parallel: 25 deg N
  • 2nd Standard Parallel: 60 deg N
  • Central Meridian: -100 deg (W)
  • Latitude of Origin: 42.5 deg N
  • False Easting: 0
  • False Northing: 0

The Daymet algorithm manages the large number of input data and large spatial extent of the study area by creating a system of 2 degree x 2 degree tiles that are processed individually through the Daymet software. These tiles are identified by a TileID that is derived within the Daymet algorithm and is consistent throughout the temporal period of the Daymet record.

The Daymet calendar is based on a standard calendar year. All Daymet years have 1 - 365 days, including leap years. For leap years, the Daymet database includes leap day. Values for December 31 are discarded from leap years to maintain a 365-day year.

Annual Climate Summaries on a 1-km Grid for North America, Version 4 R1

Filename format: daymet_v4_<pppp>_ann<xxx>_<region>_<yyyy>.<ext>, where:

<pppp> is the respective parameter abbreviation (prcp, swe, tmax, tmin, and vp),
<xxx> is the summary, either 'avg' (average) or 'ttl' (total),
<region> is either 'na' (for continental North America), 'hi' (for hawaii), or 'pr' (for Puerto Rico),
<yyyy> is year (1950 through 2023), and
<ext> is file format extension, either 'nc' (netCDF) or 'tif' (Cloud-Optimized GeoTIFF)

Example filename: daymet_v4_tmax_annavg_na_2014.nc

Daily Surface Weather Data on a 1-km Grid for North America, Version 4 R1

Filename format: daymet_v4_daily_<region>_<pppp>_<yyyy>.nc, where:

<region> is either 'na' (for continental North America), 'hi' (for hawaii), or 'pr' (for Puerto Rico),
<pppp> is the respective parameter abbreviation (dayl, prcp, srad, swe, tmax, tmin, and vp), and
<yyyy> is year (1950 through 2023).

Example filename: daymet_v4_daily_na_prcp_2014.nc

Sub-daily Climate Forcings for Puerto Rico

The file naming convention is  clmforce.Daymet4_<reanalysis_ds>_PR.1km.<var>.<yyyy-mm>.nc, where:

<reanalysis_ds> =  the meteorological reanalysis dataset 'GSWP3' or 'NARR' 
<var> = the file variable(s) desription abbreviation ('Prec', 'Solr', 'TPQWL') 
<yyyy-mm> =  the year-month date range of the file

Example filename: clmforc.Daymet4_GSWP3_PR.1km.Prec.1950-01.nc

Daymet Version 4 Monthly Latency: Daily Surface Weather Data

Filename format: daymet_v4ll_daily_<region>_<pppp>_<yyyy><mm>.nc, where:

<region> 'na' (continental North America), 'pr' (Puerto Rico), 'hi' (Hawaii)
<pppp> is the respective parameter abbreviation (dayl, prcp, srad, swe, tmax, tmin, and vp), 
<yyyy><mm> is year and month

Example filename: daymet_v4ll_daily_na_tmax_202101.nc

Monthly Climate Summaries on a 1-km Grid for North America, Version 4 R1

Filename format: daymet_v4_<pppp>_mon<xxx>_<region>_<yyyy>.<ext>, where: 

<pppp> is the respective parameter abbreviation (prcp, swe, tmax, tmin, and vp),
<xxx> is the summary, either 'avg' (average) or 'ttl' (total), 
<region> is either 'na' (for continental North America), 'hi' (for hawaii), or 'pr' (for Puerto Rico),
<yyyy> is year (1950 through 2022), and
<ext> is file format extension, either 'nc' (netCDF) or 'tif' (Cloud-Optimized GeoTIFF)

Example filename: daymet_v4_tmin_monavg_na_1988.nc

Station-Level Inputs and Cross-Validation for North America, Version 4 R1

Filename format: daymet_v4_stnxval_<pppp>_<region>_<yyyy>.nc, where:

<pppp> is the respective meteorological variable (tmax, tmin, and prcp)
<region> is 'na' (for continental North America), 'hi' (for Hawaii), or 'pr' (for Puerto Rico), and
<yyyy> is year (1950 through 2022)

Daymet data are openly shared, without restriction, in accordance with the NASA Earth Science program Data and Information Policy.

Proper citations include the authors, title, publisher, and Digital Object Identifier (DOI) and will allow the products to be discovered and re-used by others.

Daymet Dataset Citations

For full citation information, click on the appropriate dataset DOI below:

Daymet methods used to generate data products:

  • Thornton, P. E., R. Shrestha, M. Thornton, S.-C. Kao, Y. Wei, and B. E. Wilson. 2021. Gridded daily weather data for North America with comprehensive uncertainty quantification. Scientific Data 8. https://doi.org/10.1038/s41597-021-00973-0
  • Thornton, P.E., Running, S.W., White, M.A. 1997. Generating surfaces of daily meteorological variables over large regions of complex terrain. Journal of Hydrology 190: 214 - 251. https://doi.org/10.1016/S0022-1694(96)03128-9

For applications of radiation and humidity data, please include the following citations in addition to the general citation:

  • Thornton, P.E., H. Hasenauer, and M.A. White. 2000. Simultaneous estimation of daily solar radiation and humidity from observed temperature and precipitation: An application over complex terrain in Austria. Agricultural and Forest Meteorology 104:255-271. https://doi.org/10.1016/S0168-1923(00)00170-2
  • Thornton, P.E. and S.W. Running. 1999. An improved algorithm for estimating incident daily solar radiation from measurements of temperature, humidity, and precipitation. Agriculture and Forest Meteorology. 93:211-228. https://doi.org/10.1016/S0168-1923(98)00126-9