The difference between downwelling shortwave hemispheric irradiance and derived
downwelling shortwave hemispheric irradiance was larger than normal (>50W/m2) and was most
noticeable at lower zenith angles. The problem spontaneously resolved itself on 7/16 without any
specific callouts by the GRW cleaning personnel on their reports. Short_direct_normal
datastream is suspected to be low due to potentially dirty NIP instrument window during
this time period. The commencement of this problem corresponds with a rain event early
7/12. The possibility of other radiometers affected by dirty domes is also possible.
Longwave instruments are typically immune to this level of contamination. |