With the background over the last few columns, let’s try and make a little sense of what weather is and why we receive the weather we do. Please, this is just a very condensed version so if you something doesn’t make sense or you would like more information, e-mail me at martinv@bartonccc.edu. As we do this remember equilibrium, lowest energy state, gradients, moving from higher to lower, and the three-dimensional nature of our weather.
• The energy and gradients that create our weather/climate result from solar energy and its unequal distribution across the planet. In general, the further you are from the equator, the less energy you receive.
• The energy, radiation, from the sun comes in the form of waves. These waves include the visible spectrum and waves invisible to our eyes, especially long-wave or infrared radiation. Some of this energy is reflected back into space and some absorbed by everything from the oceans and plants to soil and buildings. All these surfaces also reflect some solar energy as visible (think color) or infrared (heat) waves.
• The energy from the sun warms the atmosphere as well as everything on earth and is also used to convert water from a solid to liquid to vapor (humidity). The more energy used to convert water to a higher energy state, the less heating of the atmosphere that can take place.
• As the surface accumulates heat, the air near the surface heats up and rises since it is warmer than the air higher up. As this occurs, the air cools and as it cools it can hold less water. If it rises enough, the air loses sufficient energy (heat) and becomes saturated (100 percent) humidity. Clouds then form and if updrafts and moisture are sufficient, we can receive precipitation.
• There are circulation cells in the atmosphere. If air moves from higher to lower pressure at the surface, it will accumulate and rise. As it rises and air accumulates, the pressure aloft is higher than other areas so that air will move aloft towards lower pressure. This results in higher pressure above an area and the air will sink. When it sinks, it heats up and as it done it can hold more water vapor. Areas of rising air tend to be cloudier and have more precipitation. Areas of descending air tend to have few clouds and are dry. This can occur on scales from the very small to the global.
• The equator and 60 degrees north and south latitude are areas of ascending air and tend to be cloudy and rainier. Thirty and 90 (the Poles) degrees are areas of descending air and are relatively cloudless and dry. Look on a map and the major deserts of the world are in proximity of these latitudes. And just because they are cold, the poles are essentially deserts.
• There are places that “cause” weather and places that “receive” weather. The equator (0 degrees latitude) and 30, 60, and 90 (the Poles) degrees north and south latitude are weather “makers” while areas like ours are “receivers.”
• When the area of high pressure and descending air south of here is particularly strong and builds it blocks low pressure and keeps it north of here which has given us this year’s brutal weather.
Next week will get back to more agricultural topics after tying up a few loose ends regarding the Jetstream and ocean currents.
Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.