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Kempsville Middle School ’s Weather Terms
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Yahoo Dictionary
http://kids.yahoo.com/reference/dictionary/english/index

Weather Channel Glossary
http://www.weather.com/glossary/a.html

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Atmosphere
Earth’s air, which is make up of a thin layer of gases, solids, liquids; forms a protective layer around the planet and is divided into five distinct layers.

Air Pressure
the pressure exerted by the atmosphere

Climate
Average weather pattern in an area over a long period of time; can be classified by temperature, humidity, precipitation, and vegetation.

Troposphere
Layer of Earth’s atmosphere that is closest to the ground.

Stratosphere
Layer above the troposphere, contains the ozone layer; extends fro 10 km-50 km.

Thermosphere
Named for its high temperatures, thickest layer of the atmosphere; found between 85 km- 500 km above the earth’s surface

Mesosphere
Extends from the top of the stratosphere to about 85 km above the earth; usually where “shooting stars” are seen

Exosphere
Has few molecules; last layer of the atmosphere; this is the layer the space shuttle orbits in.

Ionosphere
Layer of electrically charged particles in the thermosphere that absorbs AM radio waves during the day and reflects them back at night.

Ozone layer
Layer within the stratosphere with high concentrations of ozone; absorbs most of the sun’s harmful ultraviolet radiation.

Wind
Results when air moves from regions of high pressure to regions of low pressure.

Jet stream
Narrow belt of strong winds that blows near the top of the troposphere.

Humidity
Amount of water vapor held in the air.

Relative humidity
Measure of the amount of moisture held in the air compared with the amount it can hold at a given temperature; can range from 0-100 percent.

Dew point
Temperature at which air is saturated and condensation forms.

Fog
A stratus cloud that forms when air is cooled to its dew point near the ground.

Precipitation
Water falling from the clouds, including rain, snow, sleet, and hale; form is determined by air temperature.

Front
Boundary between two air masses with different temperatures, density, or moisture; can be cold or warm.

Tornado
A violent, whirling, wind that moves in a narrow path over land.

Hurricane
Large, sever storm that forms over tropical oceans, has winds of least 120 km/h, and loses power when it reaches land.

Meteorologist
A scientist who studies weather and uses information from Doppler radar, weather satellites, computer and other instruments to make weather maps and provide forecasts.

Cold Front
Occurs when colder air advances toward warm air; temperature difference is usually large between the cold and warm air and thus thunderstorms or even tornadoes may form.

Warm Front
Forms when warmer air advances over heavier, colder air; usually brings wet weather.

Particulate Matter
Solid particles and liquid droplets suspended in the air.

Weather
Refers to the state of the atmosphere at a specific time and place; describes such conditions such as air pressure, wind, temperature, and the amount of moisture in the Atmosphere

Bonus terms

Weather Instruments: What do they measure/see?

ANEMOMETER
An instrument that measures the speed or force of the wind .

BAROMETER
An instrument used to measure atmospheric pressure . Two examples are the aneroid barometer and the mercurial barometer .

BAROMETRIC PRESSURE
The pressure exerted by the atmosphere at a given point. Its measurement can be expressed in several ways. One is in millibars. Another is in inches or millimeters of mercury (Hg) .

MILLIBAR (MB)
The standard unit of measurement for atmospheric pressure used by the National Weather Service . One millibar is equivalent to 100 newtons per square meter. Standard surface pressure is 1,013.2 millibars

INCHES OF MERCURY (Hg)
The name comes from the use of mercurial barometers which equate the height of a column of mercury with air pressure . One inch of mercury is equivalent to 33.86 millibars or 25.40 millimeters. First devised in 1644 by Evangelista Torricelli (1608-1647), an Italian physicist and mathematician, to explain the fundamental principles of hydromechanics.

THERMOMETER
An instrument used for measuring temperature . The different scales used in meteorology are Celsius , Fahrenheit , and Kelvin or Absolute .

RADAR
Acronym for RA dio D etection A nd R anging. An electronic instrument used to detect distant objects and measure their range by how they scatter or reflect radio energy. Precipitation and clouds are detected by measuring the strength of the electromagnetic signal reflected back.

SATELLITE
Any object that orbits a celestial body, such as a moon. However, the term is often used in reference to the manufactured objects that orbit the earth, either in a geostationary or a polar manner. Some of the information that is gathered by weather satellites, such as GOES9, includes upper air temperatures and humidity, recording the temperatures of cloud tops, land, and ocean, monitoring the movement of clouds to determine upper level wind speeds, tracing the movement of water vapor, monitoring the sun and solar activity, and relaying data from weather instruments around the world.

DOPPLER RADAR
Weather radar that measures direction and speed of a moving object, such as drops of precipitation , by determining whether atmospheric motion is horizontally toward or away from the radar. Using the Doppler effect, it measures the velocity of particles. Named for J. Christian Doppler, an Austrian physicist, who in 1842 explained why the whistle of an approaching train had a higher pitch than the same whistle when the train was going away.

Cloud Types
Cirrus – Low level clouds, smooth layers, fair weather or precipitation
Cumulous – Mid-high level clouds, puffy masses, fair weather or thunderstorms
Stratus – High level clouds, fibrous or curly, fair weather.

Weather Related Phenomena

DROUGHT
Abnormal dry weather for a specific area that is sufficiently prolonged for the lack of water to cause serious hydrological imbalance.

SNOW
Frozen precipitation in the form of white or translucent ice crystals in complex branched hexagonal form. It most often falls from stratiform clouds, but can fall as snow showers from cumuliform ones. It usually appears clustered into snowflakes.

HAIL
Precipitation that originates in convective clouds, such as cumulonimbus, in the form of balls or irregular pieces of ice, which comes in different shapes and sizes. Hail is considered to have a diameter of 5 millimeter or more; smaller bits of ice are classified as ice pellets, snow pellets, or graupel. Individual lumps are called hailstones.

THUNDERSTORM
Produced by a cumulonimbus cloud, it is a microscale event of relatively short duration characterized by thunder , lightning, gusty surface winds, turbulence , hail , icing , precipitation , moderate to extreme up and downdrafts , and under the most severe conditions , tornadoes .

HIGH PRESSURE SYSTEM
An area of relative pressure maximum that has diverging winds and a rotation opposite to the earth's rotation. This is clockwise the in Northern Hemisphere and counterclockwise in the Southern Hemisphere. It is the opposite of an area of low pressure or a cyclone .

LOW PRESSURE SYSTEM
An area of a relative pressure minimum that has converging winds and rotates in the same direction as the earth. This is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Also known as an cyclone , it is the opposite of an area of high pressure , or a anticyclone.

WATER CYCLE
The vertical and horizontal transport of water in all its states between the earth, the atmosphere , and the seas .