DAYMET
Shane Walker, CRWR
Table of Contents
Daymet is a model that generates daily surfaces of temperature, precipitation, humidity, and radiation over large regions of complex terrain. Daymet was developed at the University of Montana, Numerical Terradynamic Simulation Group (NTSG), to fulfill the need for fine resolution, daily meteorological and climatological data necessary for plant growth model inputs
Using a digital elevation model and daily observations of minimum and maximum temperatures and precipitation from ground-based meteorological stations, an 18 year daily data set (1980 - 1997) of temperature, precipitation, humidity and radiation has been produced as a continuous surface at a 1 km resolution. A wide range of summary and point daily data over the conterminous United States are now available.
No other data at this temporal and spatial resolution exists. This data is currently being distributed, free of charge, from the NTSG lab through its outreach component, the EOS Training Center Natural Resource Project.
The Daymet U.S. database is indexed by the Oak Ridge National Laboratory, Distributed Active Archive Center (ORNL DAAC), in their list of Regional and Global Data for Global Change Research
(taken from http://www.daymet.org/)
Daily Surface Weather Point Data
Daily surface weather can be accessed for a single geographic coordinate point (latitude, longitude) within the conterminous United States. A text table (shown below) of data is returned in the web page; an optional summary data file can be downloaded.
... ... ... ... ... ... ... ... ...
2003 365 18.00 -2.00 12.50 0.00 948.70 339.20 36288
Summary maps of a 1 km grid of the conterminous United States can be accessed for a each variable selection and temporal selection. A User's Guide explains parameter definitions and includes instructions for converting the .fltimg file to a Raster. A toolbox created at CRWR is provided that includes a model tool to convert the binary grid to a projected ESRI raster. Sample .jpg maps are below of precipitation and temperature, respectively.
A) Variable Selection
(1) Temperature
1. Daily maximum air temperature
2. Daily minimum air temperature
3. Daily average air temperature
4. Day-to-day variability in maximum temperature
5. Day-to-day variability in minimum temperature
6. Day-to-day variability in average temperature
7. Number of frost days
8. Growing degree-days
9. Heating degree-days
10. Cooling degree-days
(2) Precipitation
1. Precipitation frequency
2. Average precipitation event size
3. Total precipitation
(3) Radiation
1. Daily total short-wave radiation
2. Day-to-day variability in total short-wave radiation
(4) Humidity
1. Daily average water vapor pressure
2. Day-to-day variability in vapor pressure
B) Temporal Selection
(1) Annual – Period of Record (1980-1997)
1. 18-year mean
2. 18-year interannual standard deviation
(2) Monthly (e.g., January)
1. 18-year mean
2. 18-year interannual standard deviation
(3) Annual (e.g., 1980)
C) File-format Selection
(1) Floating-point binary data (4587 x 2889 pixels - *.fltimg)
(2) Plotter size color map (34” x 22” - *.pdf)
(3) Letter size color map (8.5” x 11” - *.jpg)
Peter E. Thornton (thornton@ucar.edu)
National Center for Atmospheric Research
Climate and Global Dynamics Division
1850 Table Mesa Dr.
Boulder, CO 80307
Phone: (303) 497-1727
These materials may be used for study, research, and education, but please credit the authors and the Center for Research in Water Resources, The University of Texas at Austin. All commercial rights reserved. Copyright 2004 Center for Research in Water Resources.
