climatology and meteorology


a nearly colorless (but faintly blue) gaseous form of oxygen, with a characteristic odor like chlorine; has a formula of O3 and a molecular weight of 48; found in trace quantities in the earth's atmosphere at all times, primarily in the stratosphere between heights of about 10 to 50 kilometers (6 to 31 miles; the ozonosphere or ozone shield) where its production results from photochemical processes involving ultraviolet radiation; its maximum concentration occurs between 20 to 25 kilometers (12 to 16 miles); in the lower atmosphere, ozone is commonly formed as a product of electrical discharges through the air.

observational network

a group of stations (surface meteorological, upper-air, or other) spread over a given area for making regular observations.


a weather or meteorological observation is an evaluation of one or more meteorological elements that describes the state of the atmosphere either at the earth's surface or aloft.

North Atlantic Oscillation

an oscillation in the strength of the Icelandic Low and Azores High, the two dominant surface pressure features in the North Atlantic. When both are unusually strong, the North Atlantic Oscillation (NAO) is in its positive phase; when both are unusually weak, it is in its negative phase. The NAO has climate impacts not just in the Arctic, but in North America and Europe. The NAO, identified by Sir Gilbert Walker in the 1920s, is similar to the Arctic Oscillation.

North American high

the relatively weak general area of high pressure which, as shown on mean charts of sea-level pressure, covers most of North America during winter; this pressure system is not nearly as well-defined as the analogous Siberian high.


a principal cloud type (cloud genus); gray and often dark; rendered diffuse by more or less continuously falling rain, snow, sleet, etc. of the ordinary varieties and not accompanied by lightning, thunder, or hail; precipitation in most cases reaches the ground; may or may not merge with low, ragged clouds that frequently occur below.

net terrestrial radiation

difference between the downward and upward terrestrial radiation fluxes; net flux of terrestrial radiation.

net budget

the difference between accumulation and ablation; usually expressed in terms of volumes of water equivalent per unit area.

meteorological element

any one of the properties or conditions of the atmosphere which together specify the weather at a given place for any particular time (for example, air temperature, pressure, wind, humidity, thunderstorm and fog).


the region of the atmosphere between about 50 kilometers (31 miles) and 80-85 kilometers (50-53 miles), extending from the top of the stratosphere to the upper temperature minimum; it is characterized by a broad temperature maximum (near 0 degrees Celsius) at its base, from which the temperature decreases to a minimum (about -90 degrees Celsius) at the mesopause level.


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