Stratocumulus Clouds

One of the more challenging aspects of watching the clouds is tricking your brain into believing, cloud-wise, that the earth is flat. I have to override my perception that the sky is a celestial dome covering the land from horizon to horizon like a huge mixing bowl covering a plate of brownies. It is not. 

Yesterday morning I was reminded of this when I noticed these stratocumulus clouds and their dark bases--the flat bottoms I have marked with red lines. Each of the red lines--hence, each cloud, is at the same altitude above the ground. It is.

The base of the cloud marks the condensation level--the altitude at which molecules of water vapor (the invisible gaseous form of water) in the atmosphere cool to the point at which the molecules slow down, condense, then glom onto each other to form liquid water droplets. When these droplets attain a certain size, they interact (refract, reflect, scatter) sunlight in such a way that they become visible to us.

How high all of these clouds? If you check the National Weather Service for July 21 at 10:54 a.m. (you cannot calculate this on your own),  you will learn that when I photographed these clouds, the temperature was 65 degrees F and the dew point (temperature at which water vapor condenses to liquid) was 49 degrees F. Subtract the second number from the first and you get 16. Multiply that by 228 and you get 4,648. This is the number of feet above the earth these clouds were floating. With enough practice I could imagine pointing to such clouds a few years from now and saying, "Look at the those strats!* I  bet they are nearly a mile high!"

Knowing how high these clouds are means knowing how high their bases are--not their tops. Stratocumulus is considered a "low" cloud type, with a a base hovers between 2,000 and 6,500 feet.

Read here how I figured all this out two years ago. Sort of.

*No one calls them "strats."

Hands-on Cloud Identification

It's not altocumulus, mid-level clouds with individual cloudlettes the size of your thumbnail when you hold it at arm's length 30 degrees above the horizon. (Some say altocumulus are between one and three fingers wide.

It's not cirrocumulus, higher clouds with cloudlettes the size of your pinky nail (or rice grains some say).

They are larger than my fist....so they could be cumulus or stratocumlus but....

...these are even bigger than my very large outstretched hand. The clouds don't have well-defined edges, flat bases, or the look of cumulus clouds. This leaves stratocumulus--a large, lumpy cloud that forms at low altitudes and is often formed as layered stratus clouds (fog) rise as they move inland over low hills. These clouds come in a variety known as stratocumulus fractus, which are the smaller (factions) of the stratocumulus cloud as it breaks apart or evaporates.

Sure enough, when I checked the National Weather Service's forecast discussion, the morning cloud cover was described as "low clouds" and "stratus" and were predicted to rise, evaporate, and give way to mostly sunny skies.