Weather

Why we have more cloudy days in winter

It's getting to be that time of year when days are chilly and clouds are stubborn. Looking at the average amount of sunshine per month, November through March have the lowest percentage of possible sunshine in Mid-Missouri with December coming in the cloudiest with only 45% possible sunshine.

From late-fall through winter, the sun is lower in the sky, striking the ground at a smaller angle and producing less heat. The longer nights and shorter days causes the air to be colder.  As the coldest air settles to the ground, a layer of warmer air above it causes the air to be stable. Normally the atmosphere cools as you gain altitude but in a temperature inversion, it actually warms. This layer of warmer air above the cold air causes the air to be more stable. Clouds which form near this layer tend to be stratiform or more horizontally spread out and long-lasting.

During colder weather, temperatures are more likely to reach the dew point temperature, producing saturated conditions and clouds are more likely to form. Also, a more active storm track causes storm systems to move through more often, making clouds more common. Another reason for more clouds in winter, the ground surface is often high in moisture content which can occur from snow on the ground and melting snow. As this moisture evaporates into the cool air above, saturation of the air is possible and when lifted, produces clouds.


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