I would assume all equipment in a Stephenson Screen does go through the annual calibration cycle that all measuring equipment should be subjected to (certainly not to groats but defined standards) to confirm their accuracy. I now live up in the north east (I was working on a jet powered craft with the designation of K7 last weekend, what an honour!) but watched the news from my last homeland. The Met man mentioned why a place was constantly one of the highest temperature areas. It wasn't just due to the air above, but the heat releasing properties of the land below and moisture bearing properties of it. Sandy soil that threw out energy as fast as it could take it in. Doesn't that go in one direction?