Went to near to get some insight (pun intended) into why Rsw.in and Rsw.global.in don't agree nearly as well as in SOAS. Didn't solve this problem, but did find that the shield on Rlw.in was cocked -- perhaps even in the field of view of the sensor -- I took a photo.
Also decided to clean the radiometers while I was there, since I could imagine a film of dust on the SPN1, though the tissue didn't come away dirty. There were spider webs around.
Cleaning done about 15:30, though I was standing near the radiometers perhaps as much as 10min before.