So, I’m driving into work. I live in Alpine Township. When I leave, my car thermometer says 40 degrees. There is a pretty solid snowcover where I am – the wind is due south and light. I get to Alpine Avenue (which runs north/south and as I make the turn to drive south, the temperature jumps to 42. The pavement is clean – the higher March sun is heating the pavement and the south wind is blowing parallel to the road. We also have any heat from the vehicles passing.
It’s up to 43 as I turn from I-96 unto US 131…again pavement clear, wind due south and I’m driving south. By the time I reach downtown, the car thermometer is up to 46, six degrees warmer than my house. I get off the expressway as I as pull into WOOD TV8 in Heritage Hill, the temperature is back down to 42. At the station we have trees, a little snow left on the ground and some big piles of snow.
I would hazard a guess that the thermometer was reasonably accurate. I imagine 200 years ago when this area was more forest, the temperature might have been in the upper 30s.
Land use is a significant factor in changing climate on a local and regional scale. Urban areas are warmer on a sunny day and on a night with light or calm winds, where the asphalt and concrete hold the day’s heat. A Midwest planted in corn and soybeans (much of it irrigated) has less chance of setting a record high temp. now than 80 years ago.
I do love car thermometers!