I just used the opportunity of staging for ARTSE to evaluate the effect of not cleaning our radiometers during Perdigao. All of the Perdigao radiometers were packed without being cleaned, to enable this test to be done. However, it is possible that the stretchy film that is part of the NR01 packing may have wiped some stuff off of the domes. Two of these NR01s were brought back (by me) by hand – the rest are still in the seatainer.
Today, which is partly cloudy with boundary-layer Cu, we installed NR01 #7 at approximately 13:00 (local). At approximately 14:43, I cleaned it during a period when the sun disk was clear of clouds. The order was: wetting Rsw.in, Rlw.in, Rlw.out, Rsw.out, then wiping in the same order. At the end of this cleaning, I added water to the wetness sensor, left the water on for about 10s, and wiped it clean, just as an indicator flag. I ran rserial during this cleaning on a laptop.
From the rserial output, I see Rsw.in change from about 926 W/m2 before cleaning to 912 W/m2 after. Thus, the effect of the dirt/pollen/smoke/oil/etc. was an enhancement of incoming solar radiation by about 1.4%. Obviously, the primary effect of the dirt was to enlarge the image of the solar disk. This effect will be difficult to model and thus correct the data. It would have been a good idea to measure the direct and diffuse radiation separately. When I measure the other NR01, I'll also take data using the shadowing paddle.