What season is the stratosphere coldest at 40ºN?

• A. Winter
• B. Spring
• C. Summer
• D. Fall

Answer: (C)

The stratosphere is typically coldest during the winter months at 40ºN due to the dynamic nature of atmospheric layers and temperature variations associated with seasonal changes. During winter, the troposphere experiences significant cooling, which can influence the stratosphere as well, particularly through a phenomenon called stratospheric cooling. The presence of polar night conditions, reduced sunlight, and generally lower temperatures in the northern latitudes contribute to colder stratospheric conditions.

Conversely, in the summer, the stratosphere tends to warm up as sunlight increases, leading to higher temperatures in this layer of the atmosphere. Therefore, the correct understanding is that while it may feel counterintuitive initially, summer does not produce the coldest stratospheric conditions at this latitude. The stratosphere generally experiences coldest temperatures during the winter months, thanks to the effects of reduced solar heating and prevailing atmospheric circulation patterns during this season.