TWP/SKYRAD/C2 - Probable window contamination

On several occasions in early 1999, large (10 percent) differences between the global PSPs 
and the NIP were observed.  In each case, the NIP reported low relative to the direct 
flux reported by the PSPs.  These occurrences persisted for several days each time and were 
likely due to salt on one or more of the radiometers.

There was a large discrepancy in the comparison of the PSPs and NIP during December (5-10 
percent).  This discrepancy got worse through the month and then suddenly improved after 
a rain event on December 23.  There was likely salt deposited on the radiometer windows 
that was washed off in the rain.

The observer daily rounds were being modified to include more regular cleaning of 
radiometers to address this issue.

• PSP1 unshaded standard deviation(psp1_sd)
• PSP shaded standard deviation(psps_sd)
• PSP shaded mean(psps_mean)
• PSP1 mean(psp1_mean)
• NIP mean(nip_mean)
• PSP1 maximum(psp1_max)
• NIP standard deviation(nip_sd)
• NIP maximum(nip_max)
• PSP shaded minimum(psps_min)
• PSP1 unshaded minimum(psp1_min)
• NIP minimum(nip_min)
• PSP shaded maximum(psps_max)

• Downwelling Shortwave Diffuse Hemispheric Irradiance, Pyrgeometer, Minima(down_short_diffuse_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Pyranometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• Shortwave Direct Normal Irradiance, Pyrgeometer, Standard Deviation(short_direct_normal_std)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Shortwave direct normal irradiance, pyrheliometer, minima(short_direct_normal_min)
• Shortwave direct normal irradiance, pyrheliometer(short_direct_normal)
• Downwelling shortwave diffuse hemispheric irradiance, pyranometer, maxima(down_short_diffuse_hemisp_max)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Pyranometer, Standard
  Deviation(down_short_diffuse_hemisp_std)
• Down-welling unshaded pyranometer voltage(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)
• Downwelling shortwave hemispheric irradiance, pyranometer, maxima(down_short_hemisp_max)