meteorology
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The principal branches of meteorology (red) and their
links with allied sciences (yellow)
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The study of the atmosphere and its phenomena,
weather, and climate. Based on atmospheric physics, it is primarily an observational
science, whose main application is weather forecasting and control. The
rain gauge and wind vane were known in ancient times, and the other basic
instruments – anemometer, barometer,
hygrometer, and thermometer
– had all been invented by 1790. Thus accurate data could be collected;
but simultaneous observations over a wide area were impracticable until
the development of the telegraph. Since World War I observations of the
upper atmosphere have been made, using airplanes, balloons, radiosonde,
and since World War II (when meteorology began to flourish) rockets and
artificial satellites. Radar has been much
used. Meteorology may be classified by the type of phenomenon observed:
clouds, precipitation and humidity,
wind and air pressure, air temperature,
and storms. More basic is the scale of the phenomena: the microscale deals
with small, transient phenomena up to about 10 km in size and lasting, say,
1 hour; the mesoscale, those up to 200 km across and lasting a few hours;
the synoptic scale is that of daily national and continental weather maps,
while the macroscale treats of global, seasonal phenomena. The general circulation
of the atmosphere is zonal by latitude (see jet
stream). Imposed on this are disturbances – chiefly cyclones
and anticyclones – due to imbalance
of pressure and temperature. An air mass is a large region of air, roughly
homogeneous horizontally, which forms by stagnant contact with a land or
sea surface and which then moves elsewhere. When two air masses of different
properties meet, a front is formed. See also isobar;
isotherm.
Related category
• ATMOSPHERIC
PHENOMENA AND STRUCTURES
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