Sometimes the high temperature forecast can be challenging too, as cloud cover is notoriously difficult to predict. An example is Thursday's forecast for Orange, Massachusetts. There's a huge difference in the model forecasts, probably because of uncertainty in the timing and thickness of the expected cloud cover. Let's predict Tmax for Orange and see what happens. Orange is a small town in north central Massachusetts, near the Vermont and New Hampshire borders, and was named after William of Orange.
Question: How exactly do clouds hold down the daytime temperatures?
Sometimes the timing of cloud cover is difficult to predict a day in advance. In Orange, MA on Thursday morning, the conditions were clear skies and calm winds during the night, until 8 am. So there were ideal nocturnal cooling conditions and the low dipped to 28 F, colder than any of the MOS forecasts. But then the skies quickly changed to overcast and the temperature climbed to only 51, less than the majority of the MOS forecasts, despite the fact that the rain didn't arrive until the end of the day.
Answer: Clouds suppress daytime temperatures because cloud water and/or ice particles intercept some of the shortwave solar radiation that would otherwise reach and warm the ground. Some of the intercepted radiation is reflected and some is scattered or absorbed. When the coverage of clouds is more complete (overcast instead of scattered or broken) and the clouds are more dense and/or vertically thick, the reduction in radiation reaching the ground increases.
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