Solar sensor characteristics


I use a WS2000 for my weather and solar irradiance values and use them as extended variables for tacking. I have noticed some anomalous measurements which have been increasing with the approach to Summer in the US. Between about 9 AM and 1 PM I observe an increase in irradiance which is not reflected in the PV power curve. I was curious to see if it was just my unit so I found and compared it to another WS2000 in Colorado on the same day. Here are the results:

The Green curve is from the CO unit and the Gold from my unit in CA. As you can see the are very similar and suggest that the anomaly is due to the characteristics of the wavelength sensitivity of the sensor and not the actual solar irradiance since the PV output does not show the same shape curve.

The Green curve is my AC PV production. Comments welcome.