Clouds of the Day - May 8, 2020

Clear skies ahead of a large high pressure area have produced beautiful blue skies today. The air is very dry which will lead to frost and freezing temperatures tonight. Our median last frost date here is May 4th. The blue sky is striking today. The blue is caused by the scattering of sunlight by our atmosphere. The solar spectrum contains all light colors we see. Because our atmosphere scatters more blue and violet light than other colors the sky looks blue. Without our atmosphere our sky would be black. To prove it just look at the second photo below.

Clear blue sky this morning

Here is a photo taken from the Moon during the Apollo 11 mission, probably by astronaut Buzz Aldren. The photo shows black sky with Earth in the background during the lunar day. Because the Moon has no atmosphere sunlight is not scattered and the sky appears black - unlike Earth which has blue sky because of the scattering of sunlight. By the way, on average a lunar day lasts approximately 29.5 Earth days.

Apollo 11 photo probably taken by Buzz Aldren from the surface of the moon. Photo courtesy of NASA and found HERE

A few low clouds developed during the late morning and afternoon. The clouds were the result of weak updrafts during the heat of the day. Because the clouds were borderline puffy they are considered to be cumulus. Since they were weak with little vertical development we call them cumulus humilus - a humble cumulus.

All clouds fit into a High, Middle, or Low cloud family - based on their altitude. Cumulus are in the Low Family. The name is abbreviated Cu. Cumulus is one of ten principal cloud types. It forms as detached cloud elements which are usually dense with sharp distinct outlines. Cumulus have a vertical structure with rising heaps, towers or domes. Where the Sun shines on the cloud it is usually a bright white color. Its base and areas in shadow are dark.

See our cloud atlas for more information.

Cummulus

Cumulus

Today’s solar radiation chart (May 8th) shows where clouds temporarily blocked the Sun. The greatest decrease in radiation occurred as a dense cloud passed over the Sun. Other less dense clouds made only small changes in the amount of radiation reaching the sensor. When using sunlight for the generation of electricity it is clear that large changes in voltage can occur over very short time periods. The trace from late morning on the 7th shows that cloud cover was not only variable over the short term but in general the amount of generation would be much lower throughout the day compared to today.