Essential Meteorological Terms and Weather Systems

Essential Concepts in Meteorology

Glossary of Atmospheric and Geographic Terms

Solstice

The time when the sun's rays are perpendicular to the tropics.

Climate

Succession regular time rate.

Barlovento (Windward)

Face of the slope that overlooks the sea.

Sotavento (Leeward)

Face of the slope that overlooks the sea.

Gale

Clash of the masses from the poles and the tropics.

Atmospheric Depression

An air mass less than 1015 mb.

Precipitation

The water that falls to Earth's surface from clouds, in liquid or solid form. It is measured with a rain gauge and is expressed in millimeters (mm) or liters per square meter (l/m²). Precipitation is plotted on maps using isohyets, which are lines joining points with the same amount of precipitation.

Atmospheric Pressure

Atmospheric pressure is the weight of air on a location. It is measured with a barometer and is expressed in millibars (mb). It is plotted on maps using isobars, which are lines joining points with the same pressure. The normal pressure, measured at sea level, is 1015 mb.

Anticyclone

An area of atmospheric pressure above the normal level. This usually produces stable pressure conditions and an absence of precipitation.

Wind

Wind is horizontally moving air. Its speed is measured with an anemometer in km/h, and its direction is measured with a weather vane. On maps, wind is depicted with arrows indicating the direction in which it blows.

Atmospheric Circulation

Atmospheric circulation is the large-scale movement of air within the atmosphere. It is the primary medium (along with ocean circulation) by which heat is distributed across the surface of the Earth.

It should be noted that, although the role of ocean currents is smaller in terms of volume compared to atmospheric circulation, their importance in heat flow between geoastronomical areas is very large due to the remarkable difference in density between air and ocean water.

The large-scale structure of atmospheric circulation varies from year to year, but the basic structure remains constant. However, individual weather systems—such as mid-latitude depressions or tropical convective cells—occur randomly. It is accepted that the weather cannot be predicted beyond a short period of time: perhaps a month in theory, or currently, about ten days in practice. Nevertheless, the average of these systems—the climate—is very stable.

Temperature

Temperature is the degree of heat in the air. It is measured with a thermometer, expressed in degrees Celsius, and represented on maps by isotherms, which are lines connecting points with the same temperature.