Thursday, May 26, 2011

Where the heck did all this rain come from?

Seems like its been raining around here every day or so for a month or longer. The baseball season has been marred by rain delays and postponements, farmers are still waiting for the fields to dry out so they can plant crops, flash flood warnings and swelling river updates on the TV, it has been as wet a Spring as I can remember.

While I don't know beans about predicting weather I do know that the rain that falls in one location started out as water vapor absorbed into the air somewhere else.  Here is an NOAA loop of water vapor as it starts over the North Pacific and swirls to the East across the upper USA.   The psychometric chart demonstrates that as air increases in temperature it's saturation point for water increases exponentially so a small increase in air temperature can make a large increase in the amount of water a mass of air can hold.

That swirling warm humidified air mass then has to mix with another colder air mass to make the water vapor condense out as rain.  Otherwise the humid air would just pass right over without any rain falling.  There needs to be a ongoing collision of a warm humid air mass and a cold one to generate the persistent and massive rain we have seen lately here.  As long as there are polar ice caps, there will be cold air masses, and where those cold air masses collide with warm humid air masses there will be rain. 
The warmer ocean temperatures  and warmer atmosphere combine to increase the amount of moisture the atmosphere holds increasing the potential for monsoon-like weather when that warm humid airstream meets up with a cold front. Predicting exactly where, when and how much rain will fall is beyond our modeling capability but it is reasonable to say that as the ocean temperatures rise from the effects of AGW, we will see more rain, not less. And as the slow march of AGW affects ocean and wind currents, there will be regional changes in traditional weather patterns. Better or worse, the climate is going to change everywhere.

There are some 6 billion people on the planet and each one of us is using some amount of energy derived from fossil fuels every day. That process involves creating carbon dioxide, a greenhouse gas that holds heat in the air, and waste heat that goes into the air and eventually into the ocean. While an increase in temperature of the oceans might seem slight, there is a flood of data to demonstrate the exponential increase in the amount of evaporation resulting from warmer oceans and air.

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