NSA/SKYRAD/C2 - NIP Frost or Ice

Frost or ice likely obstructed the NIP as short_direct_normal values were near zero for 
the affected time periods. These times correspond to mornings before OPS has the 
opportunity to clean the instruments. Clear days at Atqusuk are rare and the NIP instrument can 
very well be ice covered and it won't be apparent in the data.  In this case the clear days 
and overnight icing made the icing issue very apparent.

Data are not recoverable.

• Instantaneous direct normal shortwave irradiance, pyrheliometer thermopile
  voltage(inst_direct_normal)

• Shortwave direct normal irradiance, pyrheliometer(short_direct_normal)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Shortwave direct normal irradiance, pyrheliometer, minima(short_direct_normal_min)
• Shortwave Direct Normal Irradiance, Pyrgeometer, Standard Deviation(short_direct_normal_std)