A guide to this section of the website
This section of the website deals with the earth's atmosphere, and particulary with the science of meteorology. Meteorology has a theoretical aspect, a branch of classical physics dealing with the statics,
A guide to this section of the website
This section of the website deals with the earth's atmosphere, and particulary with the science of meteorology. Meteorology has a theoretical aspect, a branch of classical physics dealing with the statics, dynamics and thermodynamics of the moist air that makes up the atmosphere. It also has a practical aspect, weather analysis and forecasting, which is of great practical utility to agriculture, navigation and aeronautics.
Additional information on the atmosphere can be found in the Geology section of the website, especially as a part of the earth as a whole. Atmospheric tides are also treated there, together with the familiar ocean tides.
The word meteorology is from the Greek metewrologia, which meant the discussion of high things, or astronomy. Indeed, an astronomer was a metewrologos. The adjective metewros meant high, lifted, raised, like things in the heavens, such as meteors.
The articles in this section offer a good course in meteorology, especially in the basic physics of the atmosphere. A few subjects are absent, such as the structure and movement of fronts, frontogenesis and frontolysis, and quite a few aspects of practical meteorology. However, the section will probably grow. Many internet links to sources of information are given in the individual articles, including links to satellite images and current weather maps. I have not yet found a good internet source of cloud pictures, but, after all, one has the outdoors!
Weather can be predicted to some degree by observing the state of the sky and the wind. Sailors and farmers had many empirical rules connecting clouds with weather. One curious property of weather that although it is of extreme variety and proverbial for changefulness, on the average it is remarkably constant. In a given district, the weather and its signs are a good guide to what can be expected on the average. In fact, tomorrow's weather will probably look much like today's. This statistical predictability is taken advantage of in preparing almanacs and other prognostications, but the accuracy is no more than statistical, and the predictions may prove wrong just when they are the most critical. In most cases, people are satisfied if only some of the predictions are correct. In many cases, the predictions can be stated in such a way that they can be interpreted to suit whatever happens.
The barometer and thermometer were perfected in the 17th century, and weather became quantitative. The barometer, in particular, had predictive power. A low barometer was associated with clouds, rain, storms and generally bad weather, while a high barometer implied clear skies and sunny, warm, dry weather. In fact, these explicit claims are usually displayed around the dial of an aneroid barometer. There is actually a closer relation between a falling barometer and bad weather, or a rising barometer and good weather, that with the absolute height of the barometer. It became a popular hobby to record the weather daily, which has not waned in popularity. Adding the wind, clouds, amount of precipitation and humidity, a rather good set of observations typical of a weather station can be assembled. The records assembled by 17th-century amateurs are still of value in studying long-term changes in the weather.
Synoptic weather analysis and forecasting, the assembly of data from a widely spread net of weather stations, could not really begin until the telegraph made instantaneous long-distance communications possible after 1850. When data was analyzed at a central station, the changes in the weather could be seen as they happened, and the weather at stations ahead of the weather could be advised of what to expect. For the first time, weather predictions could really be predictions, not just guesses. However, surprises continued to come over the oceans. In Britain, for example, the weather comes off the Atlantic at a much more rapid rate than a ship can sail, so weather surprises were the usual thing. Sometimes an approaching storm could be detected in the clouds, a typical sequence indicating the approach of a storm. Cable telegraphs were some help, as from Ireland to England, but mostly the weather at sea was unknowable.
The invention of radio allowed the extension of the weather observation net over the oceans, and this was one of its first important uses. Every ship became a weather station, radioing reports at regular intervals to a central office. This great advance happened by 1915, and weather prediction was of great service in the Great War. Significant theoretical advances were made during the middle of the 20th century, especially in the properties of the upper atmosphere, elucidated by such indirect methods as sound propagation and meteor trails. The importance of fronts and air masses was recognized. Aircraft made observations at altitude, but the greatest advance was the radiosonde, where the pressure, temperature and humidity of an air column from the surface to high altitudes could be determined in a few minutes. Originally clumsily called ra