White Box Technologies (WBT), in collaboration with the National Renewable Energy Laboratory (NREL), has revised the TMY3 weather files to correct inconsistencies in units for illuminances, improve the reporting of Liquid Precipitation, replace all missing records with interpolated or filled values (chiefly for visibility, ceiling height, aerosol optical depth, and albedo), and add a new variable for Present Weather. The intent of this revision is not to redo the fundamental analysis, but correct some known errors and make modest improvements in the reporting of subsidiary climate variables. The only impacts from these corrections and changes are for daylighting simulations that use the illuminance values, and for building simulations that use the liquid precipitation to model green roofs or moisture transport through the building envelope. The addition of Present Weather may be of use to simulation programs that keep track of rain or snow fall, and is also helpful in assessing the reported liquid precipitation. Filling in missing data for Visibility, Ceiling Height, etc., should have no impact on the use of the TMY3s, but improves their overall record-keeping.

For more information about the TMY3 data set, please go to http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/

The revised TMY3 files in EPW and BINM formats are available for free download on the White Box Technologies web site at  http://weather.whiteboxtechnologies.com/wd-TMY3 or by selecting File Type as “TMY3” at http:/weather.whiteboxtechnologies.com/search to search using GoogleEarth. The zip file names are unchanged, but the underlying EPW and DDY files will have the *TYA designation to distinguish them from the previous TMY3 version
A full text version of this announcement is available as PDF here.