Meteorology
Meteorology is the science that investigates the physical processes occurring in Earth's atmosphere related to weather and climate. The knowledge obtained from the study of atmospheric conditions, such as pressure, temperature, wind, humidity, precipitation, clouds and solar radiation form the basis of meteorological research and weather forecasting.
Meteorological data and research are essential to the investigation of the changes affecting the Earth's climate, they are also instrumental in establishing the patterns of weather and climatic phenomena and for the determination of the dispersion of atmospheric pollutants. Meteorological data are critical to long term studies involving acid rain patterns or ozone layer depletion.
Although they describe fundamentally similar processes and atmospheric attributes (e.g., temperature, humidity, etc.), weather relates to short term meteorological phenomena that occurs over days or weeks. In contrast, climate relates to long term conditions and processes take place over months, seasons, years, etc.
Weather conditions guide daily activities and they can affect community health. On a larger scale, weather conditions can greatly impact economic activities, including resource industries (e.g., agriculture, fisheries and forestry) and transportation and travel sector industries. Military strategists expend great effort to maintain accurate weather maps and to train personnel to accurately interpret meteorological data.
Solar radiation provides the driving force for the circulation systems of the atmosphere and the oceans. Most of the physical processes taking place in the atmosphere result from self-regulating attempts to equalize the major differences that arise from inequalities in the distribution of atmospheric heat, moisture and pressure.
One principle of primary concern to meteorologists are the dynamics of differential pressure systems. In low pressure areas surrounding air masses converge toward the center of low pressure. Accordingly, such air masses are termed converging air masses and the area itself is also referred to as an area of convergence. In contrast, in high pressure areas air masses diverge outward from the center of high pressure (diverging air masses). In both converging and diverging areas there is a Coriolis deflection of the air masses to the right in the Northern Hemisphere and to the left in the Southern Hemisphere that imparts respective clockwise and counter-clockwise rotations to pressure systems. In addition, areas of convergence and divergence in the upper atmosphere are the determining factors in the formation of high and low pressure areas that will develop on the surface. In North America, the lateral driving force of upper level systems is the jet stream, an upper air current of strong velocity flowing from west to east, but oscillating on a north-south pattern. The moving air masses are also modified by thermodynamic and dynamic changes. For example, during the ascent of an air mass over a mountain range and its descent on the leeside there are adiabatic changes of temperature that can result in hot dry winds on the lee side of mountain ranges that can, in turn, lead to warm and dry downslope winds that can contribute to the formation of deserts or desert-like climates.
A major step towards understanding weather fluctuations was made when it was realized that the changes in weather seemed related to the formation and movement of boundaries between different air masses. A front defines the area of this conflict between opposing air masses. Front models and frontal depression wave models feature a warm front and a cold front separations. The two regions have distinct cloud cover, type of precipitation, barometric pressure and temperature. Frontal models provide the basis for synoptic weather maps and were a major step toward the understanding and forecasting of weather.
During the twentieth century, scientists used increasingly complex mathematical and physical models to characterize meteorological systems. For example, in 1922, L. F. Richardson proposed the use of numerical forecasting, a method which attempts to predict the physical processes in the atmosphere by means of Newton's equations of motion, the basic principle linking the rise or fall of surface pressure to mass convergence or divergence in the overlying air column. But with the tedious calculations of pre-computer days, this model was not considered particularly useful.
Advances in computer technology and their growing application for scientific research in the second part of the twentieth century made it possible to build statistical models capable of predicting weather based on historical trends. The first computer weather forecast was issued in April 1950 by a Princeton research team. The statistical model was replaced by the dynamic model that consisted of a succession of frames, each one slightly altered with respect to the previous one. In such frames, the first frame numerically represents the actual weather conditions (e.g., temperatures, pressures, humidity, visibility and other observations). These initial conditions are then entered on a grid superimposed on the map of the forecasting region. The conditions at each grid point are then recalculated by using equations which describe the dynamics of air and heat. The results of these calculations form the next frame. The computer simulation then proceeds frame-by-frame, moving each frame a few minutes closer to the specific forecast time.
However, in 1961, research findings by Edward Lorenz at MIT showed that a slight change of the initial conditions could lead to a significant change of the simulation results. Furthermore, Lorenz realized that the real atmosphere is characterized by chaotic behavior and that, in reality, weather conditions never precisely repeat themselves. The introduction of chaos has placed a limit on how far in the future prediction by computer modeling is possible. After an analysis of mathematical variables, Lorenz estimated this time limit to be of about two weeks. In addition, because initial conditions can not usually be determined with complete accuracy, chaotic effects often produce errant results if the time frame is extended too far.
The key to modern weather forecasting is the gathering of weather data from around the globe. The rapid collection, the assembling and processing of such data are crucial elements, because such data is required to prepare and distribute reasonably accurate forecasts. Historically, developments in data acquisition technologies have had immediate and profound impacts on meteorology. For example, in 1844, Samuel Morse's invention of wireless telegraphy made it possible, for the first time, to collect weather observations over long distances. In the 1920s meteorologists began exploring the upper atmosphere with kites, balloons and airplanes and by 1940 weather stations around the globe were making upper air observations. Contemporary meteorological studies, although they still rely on extensive direct monitoring by weather balloons and other modes of atmospheric sampling, are increasingly reliant upon satellite imaging, including infra-red thermal imaging and ultraviolet studies. Microwave studies provide information about wind conditions aloft and automatic readings from commercial airliners also provide data about temperature, pressure and wind at high altitudes.
Satellites, taking pictures of whole regions, transmit images of weather systems and have been instrumental in the prediction of the path and evolution of severe storms. On ground, radar provides a detailed picture of approaching precipitation systems and the Doppler radar system can supply additional information concerning the wind patterns occurring within thunderstorms and tropical storm systems.
While technological progress has greatly expanded the horizons of meteorological research and forecasting, Improved communication systems, involving radio, telephone, all-weather CABLE TELEVISION channels and the proliferation of numerous Internet sites have also dramatically increased access to weather information. Indeed, society's basic need for accurate weather information continues to be one of the motivating forces driving advancement in the meteorological sciences.
This is the complete article, containing 1,214 words
(approx. 4 pages at 300 words per page).
