Weather Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Weather is the condition of the atmosphere in a local environment or region over a short period of time, ranging from an exact instant to a few days. This is distinct from climate, which refers to persistent atmospheric systems over larger areas and greater time periods. The atmospheric conditions may be hot or cold, dry or humid, rainy or dry, windy or calm, cloudy or clear in combination.

The atmosphere is the envelope of air that surrounds the surface of the earth. It has four layers: They are the troposphere, the stratosphere, the mesosphere, and the thermosphere. The term atmosphere also means the weight of the air pressing against the earth at any given point on earth. At sea level the weight of the air is 14.7 pounds per square inch (1.03 kilograms per square centimeter) of surface. At places below sea level such as the surface of the Dead Sea the atmospheric pressure is greater than one atmosphere. On mountaintops the atmospheric pressure is less. This natural feature of the weight of the atmosphere at various places on the earth’s surface is an important feature in the weather and in the climate.

Climate differs from weather. Weather is the immediate atmospheric conditions. Climate is the average of the weather over an area for a long period of time. Almost all weather takes place in the troposphere that extends from the surface to six to ten miles above the surface of the earth. Most of the atmosphere, water vapor and heat are in this layer.

Weather conditions involve temperature, air pressure, wind, and moisture. A weather report will combine all of these to show the weather as it is currently, or more importantly as it is expected to be in the hours or days ahead in order that people may respond appropriately.

Temperature readings measure the amount of heat in the atmosphere. The heat comes from sunlight shining on the earth. However, sunshine does not strike the earth everywhere with the same effect. At the equator the sun shines directly on the earth making the weather at the equator warm. The further from the equator and the closer to the North Pole or the South Pole the more the sun strikes the earth’s surface at an angle. In addition, as the earth rotates around the sun in its yearly circumnavigation it presents either the Northern or the Southern Hemisphere to the sun more directly, which produces summer or winter.

As the sun strikes the earth’s surface it may strike water or land. Since the oceans and the continents present different surfaces to sunshine the effect generates different amounts of heat. In desert regions the heat is reflected away from the surface of the earth. At night the radiant heat quickly turns the desert into a chilly place. However, in land areas of moisture and extensive plant growth heat is absorbed by the plants and retained in the locality. In the oceans the heat is absorbed and distributed by currents, evaporation, and by reflection in a different pattern.

Another factor affecting the temperature of the atmosphere is the greenhouse effect. This occurs because the carbon dioxide given off by humans, animals, in natural springs, or by industry blocks some of the escape of radiant heat creating conditions similar to a green house or to a thermal cover on a swimming pool.

The varying temperatures on the surface of the earth create atmospheric pressure differences. As air is heated it expands and rises. The heating of the earth at the equator, and especially in the equatorial ocean waters, sends warm air upward. In contrast, the air at the poles is colder and more condensed than warm air. The effect is that warm air creates areas of low atmospheric pressure (lows) because the weight of the atmosphere at that locality is less than in areas where low temperatures condense air and create places of high atmospheric pressure (highs). The condensing of air at the poles and the rising of air in the equator creates pressure differences between the two regions. The rising air of the equator moves toward the poles and the sinking air of the poles moves toward the equator creating wind.

Winds, which are named for the direction from which they flow, blow from highs to lows. Conversely, as cooler air moves toward a low it forces the rising warmer air to move upward more rapidly. The higher the elevation the warmer air reaches, the more it cools and contracts. The moisture in the warmer air then condenses into clouds and precipitation.

Most of the rain that falls on earth is from water vapor that evaporated from the oceans. Humidity is the amount of water vapor in the atmosphere. When a volume of air has absorbed as much moisture as it temperature and pressure will allow, then it is saturated. The dew point is the temperature at which a volume of air is saturated with moisture. If a given volume of air continues to cool beyond its dew point then moisture is converted into dew, or if cold enough, into frost. Moisture-saturated air that is cooled to the dew point that is near the ground or the ocean may also create fog. If the cooling continues, then the moisture in the air condenses into either liquid precipitation (rain) or frozen precipitation (hail, sleet, or snow).

Most places on the surface of the earth have changing atmospheric patterns that vary with the seasons. At the poles the seasons are long periods of daylight in the summer or total darkness in winter. The freezing temperatures make the poles both cold deserts where most of the moisture has been squeezed out by the lower temperatures. The weather in tropical zones is marked by periods in which it is hot and dry followed by rainy seasons.

Weather reports are of great importance to farmers, sailors, and others operating in the open such as military field commanders. Weather predictions can also be of great value to people in areas that are vulnerable to extreme weather such as tornadoes, hurricanes, blizzards or heat extremes. The weather affects humans directly and constantly. In cold weather heating for homes or businesses is needed; in hot weather protection from extreme temperatures or from dehydration is necessary. In rainy or stormy weather shelter and protective clothing are necessary to prevent hypothermia or injury or death from lightning or strong winds.

Weather affects agriculture, industry, transportation, and communications. Storms such as violent thunderstorms, tornadoes (cyclones), and hurricanes (typhoons), or even dust and sand storms can create disasters for civilization in many areas of the world.

Bibliography:

Edward Aquado and James Burt, Understanding Weather and Climate (Pearson Education, 2006);
Marq De Villiers, Windswept: The Story of Wind and Weather (Walker and Company, 2006);
Storm Dunlop, Weather (Smithsonian Institution Press, 2006);
Terry J. Jennings, Weather Patterns. (Smart Apple Media, 2005);
David Ludlum, National Audubon Society Field Guide to North American Weather (Alfred A. Knopf, 1998);
Vincent J. Schaefer and John A. Day, A Field Guide to the Atmosphere (Houghton Mifflin , 1981); Jack Williams, The Weather Book (Knopf Publishing Group, 1997).