The TMY3s for 1,020 US locations were released in 2005 to become the defacto standard set of typical year weather for the US and dependencies. However, there've been a couple of problems that have plagued the TMY3s, including inconsistent units in the illuminance values, and faulty reporting of liquid precipitation. The latter problem has not been helped by the rumors that the TMY3s do not contain liquid precipitation or that they are completely useless.
White Box Technologies (yours truly), in collaboration with NREL, has now revised the TMY3 weather files to correct these two problems, as well as adding some QC touches, among them the replacement of all missing records with interpolated or filled values for visibility, ceiling height, aerosol optical depth, and albedo, and the addition of a new variable for Present Weather.
The only impact from these changes are for daylighting simulations, e.g., Radiance, that use the illuminance values, and for building simulations, e.g., EnergyPlus, 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 details of the revision, please see this report.
The revised TMY3 files are available either on the NREL Web site in their original *TMY3.CSV format or the WBT web site in the *.epw, *.BINM, and *.FIN4 formats.
