Friday, February 28, 2014

The big H over the 4 corner states

I'm a weatherbug. I love to watch the weather to see what is happening around me. Part of what I love about Utah is that we actually have weather compared to Southern California. But I've noticed that lately, the weather has been pretty tame.

For decades, I've noticed the big H over the four corner states, a high pressure ridge that develops due to the mountain ranges in the west. Go east of that, and you get inclement weather in spades.

I've also noticed why that has happened and that there is a negative feedback loop for weather in the west. Years ago, NOAA started a survey of local gravity around the world. They found that local gravity was slightly higher in the deep south than in the west. This is due to the constant rainfall in the south that has built a tremendous water table there.

We are riding on land masses that float on the mantle, a hot layer of molten rock far below the surface of the earth. The continents float on the mantle like boats on water, but they move much more slowly. The elevation of the continents varies with density.

NOAA has estimated that the water table in the deep south has depressed the crust of the earth upon the mantle by about 1200 feet. In other words, if there were no water table there, the deep south would be about 1200 feet higher than it is now.

Contrast that with the west where, compared to the southeast, there is very little rain. In geologic time, our mountain ranges are here to stay for a long time due to the weather patterns they create. The west has been like this for millions of years and there is no change in sight in the near future. It is only as the earth has warmed that the weather pattern has become even more pronounced.

So if you're not a big fan of rain or snow, move out west. Otherwise, hang out and enjoy the snow, the rain, the hurricanes and the tornadoes.
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