About solar radiation units
The solar radiation data values in our short interval files are reported in watts per square meter to facilitate data analysis. For hourly data files this unit is also treated as watt hours per square meter per hour (Wh/m2 per hour.) When summing 5, 10, or 15-minute data files into hourly data, it is important to divide by the number of intervals in the hour to keep the units correct. For example in a five minute data file on a clear data the noon time values may vary from 900 to 1000 watts per square meter for each 5 minute interval, but the hourly average value will be the sum divided by 12 and result in the hourly value of approximately 950 watts per square meter for the hour.
For daily totals, the units are in watt hours per square meter per day. In this situation, all the hourly values are added to obtain the daily total. Note that if you are adding shorter interval data, like 5 minute data, you would need to divide by the number of time intervals in the hour to obtain the correct daily total.
© 2000, UO Solar Radiation Monitoring Laboratory.
Last revised: December 11, 2000.
Home page URL: solardat.uoregon.edu