Well before the current debate over the value of the near surface temperature record and its many possible biases, and well before Parker’s UHI studies sought to minimize the effect based on windy -vs- non windy days, J. Murray Mitchell published a paper in 1952 titled: On the Causes of Instrumentally Observed Secular Temperature Trends which was a quality study on the numerous possible effects of localized micro-site effects, as well as broader UHI effects related to population growth in cities. He created a tree chart of the known influences at the time:
He looked at a variety of possible influences, and attempted to quantify them, both for rural and urban stations. Curiously, he discovered an effect that I’ve never heard of before, the day of the week effect:
While not a fully comprehensive study, it did hint at the fact that in the USA, there was a greater percentage of the population and business at the time that observed Sunday as a day of prayer and rest.
This paper is actually a summary of three different studies, examining New Haven, CT, and the Blue Hill Meteorological Observatory for UHI related issues, plus a broader study of 77 stations examining the effect of UHI on those stations then.
It’s a good read, and provides some grounding for the current discussions on the issues. Note: A hat tip to Roger Pielke, Junior, for bringing this paper to my attention.