Comparing Rsw last night from the Kipp&Zonen, Quantum, and SPN-1 at 7, I notice that the Quantum reads very close to zero, the K&Z read an average of -1.5 W/m^2 (range -3 to 0), and the SPN-1 an average of +4 W/m^2 (range +2 to +7).  Apparently, the nighttime error is proportional to the cost of the sensor??

1 Comment

  1. Steve Oncley AUTHOR

    Apr 17, 2012

    Looking at data in 2011 for stn7, and zeroing out negative values from the K&Z, I get:

    Rsw.global.spn = 5.3 + 0.966 Rsw.in.kz (all data)

    Rsw.global.spn = 1.6 + 0.975 Rsw.in.kz (after removing spn nighttime values)

    Rsw.global = 0.4 + 0.887 Rsw.in.kz (all data)

    SPN is off by ~3% and Quantum by 11% -- not too great.