For those who suffer from seasonal affective disorder or a bit of dark-day low spirits, this is a special time of the year.
Relief is on the way! The sun is coming back...very quickly.
Consider the solar radiation reaching the surface in Seattle over the past year (below).
It was pretty depressing near the turn of the year, with values consistently below 5 (megajoules per square meter, if you want to know the units). But during the last few days we have received almost three times as much!
The length of day has also gotten longer...much longer, something shown graphically by the "Sun Graph" for Seattle (below)
This figure shows the length of day, with the light blue color indicating the period between morning and evening civil twilights. We have gained several hours of light compared to the depth of winter and are now in the period when the length of day is increasing most rapidly.
Feels very good.
For a meteorologist like myself, the return of the sun has implications far beyond its pleasant feel on the skin.
The increasing solar radiation results in the warming of the surface, while the atmosphere above remains quite cool.
The result is that temperature change with height, the cooling with height, becomes very large this time of the year...and that has big implications.
A large temperature decline with height (also called a large lapse rate) results in the atmosphere becoming unstable and convecting, not unlike the situation in a lava lamp that is heated from below (see example below).
In the atmosphere, such instability leads to fields of cumulus clouds, such as shown below.
Today, large fields of sun-driven cumulus clouds were observed all over Washington State (below).
You see all the little white dots over land across the western side of the Olympic Peninsula? Or the little white specks southwest of Spokane? Lots of cumulus clouds.
Blame the warming effects of the incipient sun of spring.
Thanks, Cliff - a question: Is there a relationship between the lapse rate and the ability to form lentincular clouds?
ReplyDeleteWe pass through Soap Lake every summer on our way to our annual family reunion which is held at the Sun Lakes resort in central Washington each July. We are still waiting for Soap Lake to erect its proposed 60-foot lava lamp in the center of town -- an idea which has been floating around for more than twenty years.
ReplyDeleteThe issue is money. Custom-manufactured sixty-foot lava lamps are expensive to buy and maintain. And these devices consume electricity, especially models which are 60 feet tall.
The bigger the lava lamp, the more electricity it consumes. Naturally.
Unfortunately, the promoters of the project missed a golden opportunity in late 2024 when they failed to quickly establish an environmental justice NGO whose stated mission was to use federal grant money to bring economic opportunity to Soap Lake.
Too late for that now. The federal government's environmental NGO gravy train has now been very suddenly and very decisively derailed. Maybe it will come back again in 2029. But I wouldn't count on it.
Thank you for the refresher, Cliff.
ReplyDeleteIt is so enjoyable to watch and understand the puffy Cauliflower Clouds on my walks.