Wednesday, August 7, 2013


A few years ago, I realized that I had a basic understanding of most of the sciences.  A big exception was meteorology.

I would look at those weather maps and glaze over.  High pressure area, low pressure area, warm fronts, cold fronts, occluded fronts, what did it all mean?  What was with all those different types of clouds?  And how could anyone even try to predict the weather?  (Unfortunately, this post won't try to explain how to predict the weather.  I will list some references that you can get more information about weather prediction from if you want to learn more.)  I vowed that at some point I'd study the atmosphere the way that I'd studied oceans, lakes, and rivers a few years ago, and biology last year.

This summer, at a time when I was having trouble finding more books on soil science, and after studying as much basic geology as I wanted, I decided it was a good time to study meteorology, the atmosphere, and the weather.

To begin with, what causes the weather, the winds in particular, and the complexity of the weather in general, is a variety of factors in the way that the sun heats the earth. The first and most basic factor is the shape of the earth, which is a sphere.  The sun's rays strike and heat up the atmosphere around the equator more than at either of the poles.  This is because the angle of the sun's rays is more direct in the tropics (close to 90 degrees at noon) than it is at the poles (where it might be, perhaps, 30 degrees).  So, as we all know, it's a lot hotter in the tropics than it is within the arctic circle.  When air is heated, it rises (ask someone who lives in a third floor apartment), and when it's cold, it sinks.  The warm air rising causes the air pressure to fall (the area becomes a low pressure zone) and the cold air sinking causes the pressure to rise (creating a high pressure area). 

If the earth were a simple ball and the sun revolved around it, this would mean air would be constantly moving from the tropics to the poles. (And air moving is, of course, wind.)  But the earth does revolve and this causes the winds to shift (in several zones).  In the northern hemisphere, this causes winds blow from west to east.  (I had learned that in New England, our weather usually comes in from the west--in this case, New York.  Now I realize that weather can travel all across the continent, beginning at the Pacific Ocean.  In Europe, the weather comes off the Atlantic and moves west.)  But the earth isn't a perfect little ball.  To begin with, two thirds of it is water, mostly the oceans.  The water takes longer to heat up and longer to cool down than the earth.  (Ask anyone who lives near the ocean.)  Then there are mountains and valleys--not to mention concrete cities that form little heat islands.  The upshot of all this complexity is our ever changing (and difficult to predict) weather.

When a warm, low-pressure area, encounters a cold, high pressure area, it creates a front.  (This was figured out during World War I by Norwegian researchers with battles on their minds.)  If warm air is in charge, it's a warm front.  If the cold air advances, it's a cold front.  If it's more complex, with cold air and warm air 'battling it out', it's an occluded front.

I could write a whole post on clouds--but I won't.  I've got a lot more things I want to write on (including more science).  The basics are that there are three main types of clouds, cirrus (high, wispy clouds made mostly of ice-crystals), stratus clouds (a layer of clouds, just hanging there--if it comes all the way down to the ground, you've got fog), and cumulus clouds (big, white, puffy--and often fair weather--clouds).  These are subdivided into ten categories: cirrus, cirrostratus, and cirrocumulus (the high atmosphere clouds), altocumulus and altostratus (the middle atmosphere clouds), stratus, stratocumulus, and nimbostratus (the low clouds), and cumulus and cumulonimbus clouds (which develop vertically, that is, up).  Obviously many of these clouds are combinations of the basic three. 'Alto' means high in Latin, but this describes the middle level clouds. More importantly, 'nimbus' refers to a rain cloud.  The nimbostratus are your ordinary rainclouds, the cumulonimbus are 'thunderclouds' bringing lightning, and often squalls, hail, and occasionally tornadoes.

This is just the slightest bit of meteorology.  I've been reading a lot of books on the subject, but there are two in particular that I'd recommend.  One is a textbook on the subject that I got out of the library:  The Atmosphere by Frederick Lutgens and Edward Tarbuck.  The other is a more readable (and sometimes humorous) treatment that was loaned to me by my brother, Spencer Christian's Weather Book by Spencer Christian with Tom Biracree.

I know I originally said that I was going to write three posts on science.  I'm still reading and learning and I want to write a few more.  Next, I'll talk about the earth's five spheres.

Quote of the Day: "The sun is the source of almost all the energy that has, is, and ever will be used on Earth... Because our world is solar powered, the sun is the engine of the global weather machine." - Spencer Christian

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