MFRSRLANG

This Langley VAP uses the shortwave narrowband direct normal irradiance measured by the multifilter rotating shadowband radiometer (MFRSR) and produces the top-of-atmosphere irradiance values for two distinct time periods during daylight hours. The first period is for morning hours, for airmass values between 6 and 2; the second period is for afternoon hours, for airmass values between 2 and 6. In addition, each Langley regression is deemed “good” or “bad.” The primary cause of a poor Langley regression is cloud contamination. Although the algorithm attempts to remove cloud contamination, some residual contamination may be present that would unacceptably increase the uncertainty of the linear fit. If the uncertainty is too large, for whatever the cause, these “bad” Langley events are discarded. Additionally, for days with completely overcast conditions, a Langley regression is not possible.