So perhaps you’ve noticed lately on sunny days forecasted highs have been lower than the actual highs by several degrees. Well… it turns out that’s not entirely true.
During the deepest part of winter when the polar vortex was regularly occurring (late December into January), we were having equipment issues. Normally, we measure temperatures inside an enclosure that has a fan running on solar power during the day and batteries at night. Unfortunately, the weather destroyed the electronics that controlled the battery charging, among other casualties.
As a quick fix, we installed a passive (fan-less) shield for our sensor. Passive shelters are fine during our normally very cloudy, windy winters. Wouldn’t you know it, the sun decided to show up and, along with it, gentle breezes! That makes for beautiful winter days in Marquette. It is also a recipe for solar-induced sensor errors.
The snow acts like a mirror to the sun and the reflected radiation gets into the sensor and heats it up. How much? A rough estimate, based on before and after tests of running with and without a fan, is 3-5 degrees F. Studies have shown that, in fact, on completely calm, sunny days over a fresh blanket of snow, errors can reach up to 18 deg F! Continue reading “Temperature Readings Just Improved!”
Over the last 30 years, the city has averaged 117.2” per year of snow. That’s based on measurements taken every morning close to the lakeshore (at the Waste Water Treatment Plant which houses the official COOP weather station for Marquette, MI).
A few days ago we added a “Seasonal Snow Total” entry to the Almanac section on the home page. This should provide some insight into the kind of winter we are having. Currently, the official weather station is seeing below average snowfall so far (55.1″) while we are experiencing above normal totals (83.6″).