Daymet Single Pixel Extraction Tool

The Daymet Single Pixel Extraction Tool provides download of daily Daymet in a CSV tabular file format for a single geographic point (pixel) and provides visualization of the queried data as a graphical visualization. This data access option allows users to enter a single geographic point by latitude and longitude in decimal degrees. A routine is executed that translates the (lon, lat) coordinates into projected Daymet (x,y) coordinates. From the Daymet dataset of daily interpolated surface weather variables, daily data from the nearest 1 km x 1 km Daymet grid cell are extracted and formatted as a table with one column for each Daymet variable and one row for each day. All daily data for selected years is returned as a single (long) table, formatted for display in the browser window or downloaded in a simple text format, suitable for import into a spreadsheet or other data analysis software. A Daymet Single Pixel Extraction Web Services API is provided. CSV file download is also possible through command utilities such as Wget and cURL.

Development and publication of the Daymet Single Pixel Extraction Tool was supported under NASA's Terrestrial Ecology Program (NASA Grant NNH10AN68I) which is a contribution of the North American Carbon Program (Thornton et al., 2011).

The Daymet Single Pixel Extraction Tool provides download of daily Daymet in a CSV tabular file format for a single geographic point (pixel) and provides visualization of the queried data as a graphical visualization.  This data access option allows users to enter a single geographic point by latitude and longitude in decimal degrees. A routine is executed that translates the (lon, lat) coordinates into projected Daymet (x,y) coordinates. From the Daymet dataset of daily interpolated surface weather variables, daily data from the nearest 1 km x 1 km Daymet grid cell are extracted and formatted as a table with one column for each Daymet variable and one row for each day. All daily data for selected years is returned as a single (long) table, formatted for display in the browser window or downloaded in a simple text format, suitable for import into a spreadsheet or other data analysis software.  A Daymet Single Pixel Extraction Web Services API is provided. CSV file download is also possible through command utilities such as Wget and cURL.

Project: Daymet

Daymet provides long-term, continuous, gridded estimates of daily weather and climatology variables by interpolating and extrapolating ground-based observations through statistical modeling techniques. The Daymet data products provide driver data for biogeochemical terrestrial modeling and have myriad applications in many Earth science, natural resource, biodiversity, and agricultural research areas. Daymet 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.

Daymet is supported by NASA through the Earth Science Data and Information System (ESDIS) and the Terrestrial Ecology Program. Daymet algorithm and processing development is also supported by the Office of Biological and Environmental Research within the U.S. Department of Energy's Office of Science.

Related Datasets: 

Thornton, M.M., R. Shrestha, Y. Wei, P.E. Thornton, and S-C. Kao. 2022. Daymet: Daily Surface Weather Data on a 1-km Grid for North America, Version 4 R1. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2129

Thornton, M.M., R. Shrestha, Y. Wei, P.E. Thornton, and S-C. Kao. 2022. Daymet: Station-Level Inputs and Cross-Validation for North America, Version 4 R1. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2132

The Daymet Single Point Extraction Tool extracts and returns Daymet daily values for each Daymet variable for a single queried x, y projected value. The most current Daymet data is being delivered to the user in terms of both Daymet software and Daymet data versions. 

The Daymet Single Pixel Extraction Tool provides daily weather data for single point (pixel) locations (Thornton et al, 2011, Devarakonda et al., 2021) in an ascii text file format for each of the seven Daymet variables.  Daymet is a data product derived from a collection of algorithms and computer software designed to interpolate and extrapolate from daily meteorological observations to produce gridded estimates of daily weather parameters. Weather parameters generated include daily surfaces of minimum and maximum temperature, precipitation, vapor pressure, radiation, snow water equivalent, and day length produced on a 1 km x 1 km gridded surface. The motivation for producing Daymet is to provide measurements of near-surface meteorological conditions where no instrumentation exists. Having estimates of these surfaces is critical to understanding many processes in the terrestrial biogeochemical system.

The Daymet Single Pixel Tool delivers the current distribution of Daymet (Thornton M.M. et al., 2022).  Complete cross-validation results for maximum temperature (Tmax), minimum temperature (Tmin), and precipitation (Prcp) are provided with the Daymet V4 data release (Thornton M.M. et al., 2022), for every input weather station and every estimation day over the 40-year period.

Tool Description

Input Specifications

The Single Pixel data access option allows a user to obtain daily Daymet data in a tabular format of variables for a single geographic point (pixel). The user specifies a single geographic point by latitude and longitude, in decimal degrees. Note that latitude values are positive for north, negative for south, while longitude values are positive for east, negative for west. All valid data points will therefore have positive latitude and negative longitude. It is necessary to place the balloon or enter a latitude/longitude pair that is on the Daymet land/water mask. The user has the option to select all Daymet variables, a single variable, or a subset of variables. Similarly, all available years of data or a subset of time can be queried.

A Daymet Single Pixel Extraction Web Services API is provided. This web service allows browser viewing (both table and graph form) or CSV file download of the data for lat/lon locations directly provided from the browser URL. CSV file download is also possible through command utilities such as Wget and cURL.

Output Process

When a user clicks “Get Data”, a routine is executed on the Daymet server to translate the (lat, lon) coordinates into the Daymet projected (x, y) coordinates using the Generalized Cartographic Transformation Package (GCTP). These coordinates are used to access the Daymet dataset of daily interpolated surface weather variables. Daily data from the corresponding 1km x 1km Daymet grid cell are extracted from the dataset and formatted as a table with one column for each output variable and one row for each day. All daily data for all available years are returned as a single (long) table, formatted for display in the browser window.  A “Download Data” link is provided to the same data in a CSV format, suitable for import into a spreadsheet or other data analysis software. A “Visualize Data” button takes the user to a graphic visualization of the individual Daymet variables for the selected year(s).

Data Format

The CSV table consists of 8 header lines, followed by daily records (one per line).

Header Lines:

• Requested latitude and longitude (decimal degrees).
• File (x, y) Lambert Conformal Conic coordinates, in meters, from the Daymet data grid corresponding to the requested (lat, lon) location.
• The Daymet tile ID within which the entered lat, lon is located.
• Elevation from the Daymet DEM (in meters above sea level) for the requested location.
• Daymet data and software version information.
• Citation information for the Daymet dataset.
• Variable names and units for the daily data columns.

 

Variables and Units:

Each daily record consists of 7 variables, described below:

year (no units): Year, repeated for each day in the year.

yday (no units): Integer representing day of year, values ranging from 1-365. Where:

• yday 1 = January 1
• yday 365 = December 31 for non-leap years or December 30 for leap-years

NOTE: All Daymet years are 1 – 365 days, including leap years. The Daymet database includes leap-days. Values for December 31 are discarded from leap years to maintain a 365-day year.

tmax (degrees C): Daily maximum 2-meter air temperature.

tmin (degrees C): Daily minimum 2-meter air temperature.

dayl (s/day): Duration of the daylight period for the day. This calculation is based on the period of the day during which the sun is above a hypothetical flat horizon.

prcp (mm/day): Daily total precipitation, sum of all forms converted to water-equivalent.

srad (W/m^2): Incident shortwave radiation flux density, taken as an average over the daylight period of the day.

swe (kg/m^2): Snow water equivalent. The amount of water contained within the snowpack.

vp (Pa): Water Vapor Pressure. Daily average partial pressure of water vapor.

 

Projection Definition

Though not directly relevant to the single pixel extraction data, the Daymet dataset is spatially referenced to the following projection.

The spatial resolution of the Daymet gridded dataset is 1 km.

The North American Daymet projection system and parameters:
Projection System:	Lambert Conformal Conic
Parameters:	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

 

Calendar

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.

Ranjeet Devarakonda, Kavya Guntupally, Michele Thornton, Yaxing Wei, Debjani Singh, and Dalton Lunga. 2021. FAIR Interfaces for Geospatial Scientific Data Searches. In Proceedings of the 1st ACM SIGSPATIAL International Workshop on Searching and Mining Large Collections of Geospatial Data (GeoSearch'21). Association for Computing Machinery, New York, NY, USA, 1–4. https://doi.org/10.1145/3486640.3491391

Thornton, Michele M, Thornton, Peter E, Cook, Robert B, Wei, Yaxing, Eby, Pete I, and Devarakonda, Ranjeet. Daymet: Gridded subdaily weather data for North America. United States: N. p., 2011. Web. https://www.osti.gov/biblio/1136824

Thornton, M.M., R. Shrestha, Y. Wei, P.E. Thornton, and S-C. Kao. 2022. Daymet: Daily Surface Weather Data on a 1-km Grid for North America, Version 4 R1. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2129

Thornton, M.M., R. Shrestha, Y. Wei, P.E. Thornton, and S-C. Kao. 2022. Daymet: Station-Level Inputs and Cross-Validation for North America, Version 4 R1. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2132

Thornton, Peter E, Thornton, Michele M, Mayer, Benjamin W, Wilhelmi, Nate, Wei, Yaxing, Devarakonda, Ranjeet, and Cook, Robert B. Daymet: Daily Surface Weather Data on a 1-km Grid for North America, Version 2.. United States: N. p., 2014. Web.
 https://www.osti.gov/biblio/1148868