Geology And Weather

The processes of weather are relatively simple yet it is so difficult to predict the weather even a a week in advance. The complexity of weather is not due to the processes of the weather itself but to the messiness of the earth's surface. The terrain of the earth; including obstacles, sources of water and uneven heating of the air affects it's density and movement.

One of the most obvious examples is that since land is quicker to both absorb and to lose heat than is water, there tends to be a sea breeze, from water to land, by day and a land breeze, from land to water, by night. The earth heats most in the tropics, causing air to rise and creating a low pressure center, while the opposite occurs in the arctic. The spin of the earth directs the prevailing winds.

Simple logic tells us that high pressure centers should form over land and low pressure centers over water for the simple reason that wet air is lighter than dry air. Likewise, high pressure should form over and snow and grass and low pressure over desert and asphalt because these surfaces absorb more heat and thus cause the air to rise. All of this is well understood.

Yet, the weather remains so difficult to forecast more than a week or so in advance. This can only mean that there must yet be factors at work that we do not understand. Much of the weather revolves around those high and low pressure centers that form. But why do they form? We cannot yet really explain why a high pressure center forms in one place and a low in another, producing the winds that flow between them.

I would like to introduce a new factor into the formation of the weather, in particular these high and low pressure centers. This new factor unvolves subterranean geology. If you wonder how much effect the underground geology of the earth might have on the weather up in the sky, the answer could be plenty.

We know that sea level across the world does not form a perfect sphere as it would seem it should. There is actually considerable variation in sea level due to gravity, although this variation is very difficult to detect from the earth's surface. This variation is due to the differing density of underlying layers of rock and the resulting non-uniformity of the earth's gravitational pull.

I got to thinking, if variations in the earth's gravity from place to place can affect sea level, why would it not also affect the density of the air from one place to another? This is not just about the unevenness of the earth's surface but about the density of the subterranean rock layers. This has got to be a factor in the weather.

We tend to think of being "up in the air" as being free of gravity. At sea level water is 800 times as heavy as air but, air is bound to the earth by gravity just as is the water in the oceans. If it were not, it would have escaped into space long ago. In fact, the air forms a kind of "ocean" around the earth just as the water does and if water is so clearly affected by gravity isn't it logical that the air is affected in a similar way?

The formation of high and low pressure centers can be explained, in part, by the "piling up" of air in areas of stronger gravity at the expense of areas with weaker gravity. A clear example of this is the so-called Canadian Shield, the heavy granitic rock that underlies the eastern half of Canada. This has got to be a factor in the high pressure centers that come down from the north across the eastern U.S. Across the globe, air piles up or becomes sparse due to underlying gravity and is guided along by the spin of the earth.