Living in the Shadowlands (for the time being)

"We live in the Shadowlands. The sun is always shining somewhere else. Round a bend in the road. Over the bough of a hill..."

C.S. Lewis (movie quote from "Shadowlands")

This quote from the movie Shadowlands is packed with religious meaning and metaphor concerning the necessity of suffering and the nature of the world we inhabit and the promised paradise to follow. It and the rest of the movie gives one a lot to think about. On the other hand I am neither a movie critic (I liked this one), nor a theologian, so I read the lines above and see instead a literal description of my home in the Great Valley of California. In my two decades in the valley, I have come to see the months from November to February as the shadow months, when a fog siege could come at any time, bringing a veil of darkness and limited visibility over everything for weeks at a time. Driving to work becomes a potential destruction derby. The constantly gray sky even effects the psyche, bringing about depression in many people.

What makes it worse is the knowledge that the sun is close by. It is shining on the cloud tops only a few hundred feet overhead, and on the slopes of the Sierra Nevada foothills only a few short miles to the east. Why is it that we have to spend all these weeks in the shadows and darkness?

To a climatologist, there is no mystery. The Great Valley is surrounded by mountain ranges, and unless a storm system is moving through, the air stagnates. In the cold months of winter, heat from the ground radiates into the atmosphere above, bring air temperatures at ground level below the dew point. Water vapor condenses into microscopic water droplets too small to sink to the ground. The landscape is hidden in ground-hugging clouds. The so-called Tule Fogs of the Great Valley are the stuff of legend. When I was growing up in Southern California, I lived in the delusion that fog was a sort of overcast thing. Things in the distance might be a bit indistinct, but you could see them. The fogs of the Great Valley cause visibility to drop to mere feet. Driving in such conditions is a crapshoot. Most people know to slow down, and even keep the windows down in the freezing weather so they can hear oncoming traffic. Unfortunately there are morons too, and deadly chain reaction accidents are disturbingly common.

Living in a place for decades gives one a perspective on changes, however gradual. It's dawned on me recently that I haven't experienced as many week-long fog sieges like those that plagued my first few years in Modesto. A recent study supports the perception that the fog has not been as pervasive as it once was. The number of foggy days in some areas has decreased by a third (20% versus 30%) in the last thirty years.  Much of the change is no doubt related to global warming, as warmer overnight temperatures mean that the dew point is reached less often. The growing population of the valley no doubt has an effect, since cities give off a great deal of heat. One more factor is the decrease in particulate air pollution, since the water droplets need a bit of dust (condensation nuclei) to coalesce around. Stagnant air basins are a great place for accumulating air pollution, but we have made great efforts to decrease the particulate levels over the decades (we are still the worst in the nation, but progress is progress).

While the lower number of foggy days and cold nights is a welcome change for commuters, it is a problem for many farmers. Many of the fruit trees grown in our valley require a series of cold nights in winter to increase production of fruits in the spring. The lack of cold days is having an effect on crop yields.

As dark and depressing as the fog can be, there are times when it provides a bit of beauty. Driving to work the other day was a shadowy journey through the pasture-lands, but the layers of fog were only a few feet off the ground, giving rise to treetops that seemed to be floating in a gray ocean. The sun peaked out over the distant Sierra Crest, and soon the fog was receding and it was the start of a beautiful sunny day.