Solar eclipses have significant impacts on local weather, some of which can be surprising.
First, many people reported a “miracle”, with clouds thinning just before the eclipse.
And the “miracle” is real but there is a scientific explanation! But first, let me show you what happened.
Just before the eclipse there are a lot of low clouds in the eclipse path in northeast Texas (see blue oval area below)
But during and immediately after the eclipse, many clouds disappeared (see below).
Divine intervention? What is the effect of the prayers of astronomical devotees?
No, it is the result of weakening solar radiation causing the surface to cool. Many of these clouds are shallow convection/accumulation, driven by the heat of the sun (see figure below). As the sun weakens, so do the clouds.
Not surprisingly, surface air temperatures cooled during the eclipse by as much as 5-10F in some locations. To illustrate, here are the temperatures in Joplin, Missouri, where temperatures rose from about 80F to 73F between 12:30 p.m. and 2 p.m., before recovering over the next hour as the sun returned .
And then there was the wind. At many locations, drama took place palliation about wind speed during the eclipse. Here are the temperatures and winds at another location in Missouri (Folly Ridge). Significant wind reduction over the entire period (from approximately 10 to 3 mph).
This can be explained by reduced vertical mixing in the lower atmosphere.
Have you ever noticed that in the warm season, the wind is stronger in the afternoon and weaker at night? During the day, the sun’s heat at the surface causes vertical mixing, which carries strong winds (not slowed by rough surfaces) down to the surface. As the sun weakens, mixing weakens, reducing the flow of stronger winds to the surface.
Finally, there’s another change that I’m not sure can be explained– so perhaps I’d better be careful about taking divine intervention lightly.
What am I talking about? Changes in weather radar images.
Consider a radar image from Dallas, Fort Worth, early in the morning (1406 UTC or 9 a.m. Dallas time). Not much radar echo.
After three and a half hours (12:34 p.m.), there were many weak radar echoes.
But an hour later, near the peak of the eclipse, there was very little echo…like night.
And then an hour later, when the sun returned, the echo returned.
What is going on here? What are these echoes? Do birds or bugs like to fly during the day? I’ll have to dig deeper into this.
In summary, by significantly altering the heating characteristics of the lower atmosphere, the eclipse caused some profound but temporary effects on many weather parameters.
