atmosphere

ozone

• a colorless unstable toxic gas with a pungent odor and powerful oxidizing properties, formed from oxygen by electrical discharges or ultraviolet light. It differs from normal oxygen (O2) in having three atoms in its molecule (O3).

troposphere

• the lowest region of the atmosphere, extending from the earth's surface to a height of about 3.7–6.2 miles (6–10 km), which is the lower boundary of the stratosphere.

stratosphere

• the layer of the earth's atmosphere above the troposphere, extending to about 32 miles (50 km) above the earth's surface (the lower boundary of the mesosphere).

mesosphere

• the region of the earth's atmosphere above the stratosphere and below the thermosphere, between about 30 and 50 miles (50 and 80 km) in altitude.

thermosphere

• the region of the atmosphere above the mesosphere and below the height at which the atmosphere ceases to have the properties of a continuous medium. The thermosphere is characterized throughout by an increase in temperature with height.

conduction

• the process by which heat or electricity is directly transmitted through a substance when there is a difference of temperature or of electrical potential between adjoining regions, without movement of the material.

convection

• the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.

radiation

• the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles that cause ionization.

greenhouse effect

• The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) the atmosphere will radiate energy in all directions.

sublimation

• Sublimation is a chemical process where a solid turns into a gas without going through a liquid stage. An example of sublimiation is when ice cubes shrink in the freezer.

deposition

• Deposition is the geological process in which sediments, soil and rocks are added to a landform or land mass. Wind, ice, and water, as well as sediment flowing via gravity, transport previously eroded sediment, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.

humidity

• a quantity representing the amount of water vapor in the atmosphere or a gas.

dew point

• the atmospheric temperature (varying according to pressure and humidity) below which water droplets begin to condense and dew can form.

hygrometer

• an instrument for measuring the humidity of the air or a gas.

air pressure

• is the force exerted onto a surface by the weight of the air. An example of air pressure is the average sea-level air pressure of 101.325 kPA.

barometer

• an instrument measuring atmospheric pressure, used especially in forecasting the weather and determining altitude.

Coriolis effect

• an effect whereby a mass moving in a rotating system experiences a force (the Coriolis force ) acting perpendicular to the direction of motion and to the axis of rotation. On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather systems.

jet stream

• a narrow, variable band of very strong, predominantly westerly air currents encircling the globe several miles above the earth. There are typically two or three jet streams in each of the northern and southern hemispheres.

cyclone

• a system of winds rotating inward to an area of low atmospheric pressure, with a counterclockwise (northern hemisphere) or clockwise (southern hemisphere) circulation; a depression.

anticyclone

• a weather system with high atmospheric pressure at its center, around which air slowly circulates in a clockwise (northern hemisphere) or counterclockwise (southern hemisphere) direction. Anticyclones are associated with calm, fine weather.

anemometer

• an instrument for measuring the speed of the wind, or of any current of gas.

El Nino

• is an abnormal weather pattern that is caused by the warming of the Pacific Ocean near the equator, off the coast of South America. This occurs when the normal trade winds weaken (or even reverse), which lets the warm water that is usually found in the western Pacific flow instead towards the east.

La Nina

• an irregularly recurring upwelling of unusually cold water to the ocean surface along the western coast of South America that often occurs following an El Niño and that disrupts typical regional and global weather patterns especially in a manner opposite to that of El Niño.

air mass

• a body of air with horizontally uniform temperature, humidity, and pressure.

front

• The boundary between two air masses that have different temperatures or humidity. In the mid-latitude areas of the Earth, where warm tropical air meets cooler polar air, the systems of fronts define the weather and often cause precipitation to form.

warm front

• the boundary of an advancing mass of warm air, in particular the leading edge of the warm sector of a low-pressure system.

cold front

• as the transition zone where a cold air mass is replacing a warmer air mass. Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it.

stationary front

• s a pair of air masses, neither of which is strong enough to replace the other. On a weather map, this is shown by an inter-playing series of blue spikes pointing one direction and red domes pointing the other.

occluded front

• a composite front produced by occlusion.

thunderstorm

• a storm with thunder and lightning and typically also heavy rain or hail.

tornado

• a mobile, destructive vortex of violently rotating winds having the appearance of a funnel-shaped cloud and advancing beneath a large storm system.

hurricane

• a storm with a violent wind, in particular a tropical cyclone in the Caribbean.

global warming

• a gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide, chlorofluorocarbons, and other pollutants.