Stratocumulus clouds are one of the most common worldwide clouds and are an excellent indicator of moisture content in the lower atmosphere. Stratocumulus is a low cloud, with its base usually below 7000 ft. It forms patches, sheets or extensive layers of grey and white cloud and has a ragged appearance along its upper surface but may have a flat, well-defined base. Stratocumulus clouds tend to form in fairly shallow layers which can be several hundred miles wide.
Stratocumulus clouds from when rising air (lifted by a frontal system or a land mass) meets a layer of warm air and is flattened against its underside. As it is lifted the moisture in the air condenses and produces the Stratocumulus clouds. In winter stratocumulus clouds produce a cloudy, overcast sky that can last for many days, but in summer the clouds tend to burn off with the heat of the day. As with stratus clouds, stratocumulus can produce light drizzle or snow grains in cold temperatures, but generally precipitation is very limited.
Stratocumulus will often give a sheet of almost complete cloud cover. The colour of the cloud varies from light to dark grey depending on the light conditions and the thickness of the clouds. The convection within the cloud causes a more lumpy appearance and this distinguishes it from the flatter stratus cloud.
Meteorologically speaking there are two types of stratocumulus. Firstly, on windy days stratocumulus will form at approximately 1500 ft due to turbulence caused as the wind blows over hills, trees and buildings. Secondly, on calmer days the cloud base may be between 2000 and 7000 ft and is caused by weak convection currents higher up. In this case imagine the stratocumulus cloud sheet as a moist layer floating at 2000 ft unrelated to its surroundings and thick enough (approx 1000 ft) to give just the occasional spot of rain. If this weak convection becomes more substantial then the stratocumulus may develop into cumulus, or even potentially cumulonimbus.
If the cloud hasn’t developed into cumulus by mid afternoon then there is unlikely to be sufficient convection and the cloud will slowly start to dissipate leaving the evening sky clear and fine.
Stratocumulus can form huge sheets of cloud covering many thousands of square miles, particularly around a high pressure system. This is even more pronounced over the oceans where there is a plentiful supply of moisture. The weather under such overcast clouds can be dry with just the occasional spot of rain, but also tends to be very gloomy, and often for several days as high pressure systems can be so difficult to move on.
So in summary stratocumulus clouds can be found all year round, in any location on the planet, and are one of the most common types of cloud we have. They are caused by the lifting of a large air mass and subsequent condensation. And finally theses clouds produce very little precipitation, but can cause a long lasting stratocumulus gloom when trapped on the flanks of an Anticyclone.