US National Weather Service Philadelphia/Mount Holly
A little bit of science on the night shift: This picture was taken Monday afternoon over the lower Delmarva Peninsula, but it is a common phenomenon for our area, especially this time of year.
Have you ever been at the shore and noticed that the clouds seem to stop right at the beach, while over the ocean there aren't any clouds? In the case in the picture below, the clouds shown are cumulus clouds and the reason these are confined to land areas is related to something called specific heat. Specific heat is a physics term that is a measure of how much energy is needed to raise the temperature of a material. The specific heat of water is much higher than the specific heat of land, so land will often warm up faster than water. With the land at a higher temperature, the air just above the land also becomes warmer than the air above the water. The warmer air begins to rise, and (if there is enough moisture in the air) clouds are formed.
2 comments:
Duh, nothing but weather 101 class material. Boring...
I thought everyone, at least those living at or near the beach, already knows about land heating and cooling faster than water. And that it is the reason for cooler sea breezes during the day, and warm land breezes at night, along the ocean. That's what makes the beach a cooler place to be on hot summer days, and what draws all the insects to the beach at night when they come in with the land breeze from the inland marshes. As the land heats up during the day, heat rises above the land, and the cooler air off the ocean rushes in producing the cool breeze at the beach. At night the effect is reversed and the now warmer ocean draws the cooler land air towards the beach. I guess you have to live at, or spend a lot of time at the seashore, if you don't think any of this is unusual. It is way overcomplicating the obvious by trying to apply "specific heat" as an explanation. The concept is simple: Warmed air rises, and cool air sinks. Warmed moist air rises and makes clouds. That's all there is to it.
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