Weather Factors

Chapter Two

Energy in the Atmosphere

Most energy from the sun reaches Earth in the form of visible light and infrared radiation, and a small amount of ultraviolet radiation.

When Earth’s surface is heated, it radiates some of the energy back into the atmosphere as infrared radiation.

Key Terms: Electromagnetic waves: A form of energy that can travel

through space. Radiation: The direct transfer of energy by

electromagnetic waves. Infrared radiation: A form of energy with wavelengths that

are longer than visible light. Ultraviolet radiation: A form of energy with wavelengths

that are shorter than visible light. Scattering: Reflections of light in all directions Greenhouse Effect: The process by which heat is

trapped in the atmosphere by wayer vapor, carbon dioxide, methane, and other gases that form a “blanket” around Earth.

Heat Transfer

The energy of motion in the molecules of a substance is called thermal energy.

Three forms of heat transfer work together to heat the troposphere. They are: Radiation

Conduction

Convection

Key Terms Thermal energy: The energy of motion in the molecules of a

substance. Temperature: The average amount of energy of motion in the

molecules of a substance. Thermometer: An instrument used to measure temperature

consisting of a thin, glass tube with a bulb on one end that contains a liquid (usually) mercury or alcohol.

Heat: The energy transferred from a hotter object to a cooler one.

Conduction: The direct transfer of heat from one substance to another substance that is touching.

Convection: The transfer of heat by the movement of a fluid.

Winds

All winds are caused by differences in air pressure.

Local winds are caused by unequal heating of Earth’s surface within a small area.

The movement of air between the equator and the poles produces global winds.

The major global wind belts are the trade winds, the prevailing westerlies and the polar easterlies.

Key Terms Wind: The horizontal movement of air from an area of high pressure to

an area of lower pressure. Anemometer: An instrument used to measure wind speed. Wind-chill factor: Increased cooling caused by the wind. Local wind: Winds that blow over short distances. Global wind: Winds that blow steadily from specific directions over

long distances. Sea Breeze: The flow of air from an ocean or lake to the land. Land breeze: The flow of air from land to a body of water. Coriolis effect: The way Earth’s rotation makes winds in the Northern

Hemisphere curve to the right and winds in the Southern Hemisphere curve to the left.

Latitude: The distance from the equator, measured in degrees.

Water in the Atmosphere

Clouds of all kinds form when water in the air becomes liquid water or ice crystals.

Types of Clouds

Meteorologists classify clouds into three main types: Cumulus

Stratus

Cirrus

Key Terms Evaporation: The process in which water molecules iin liquid water

escape into the air as water vapor. Humidity: A measure of the amount of water vapor in the air. Relative humidity: The percentage of water vapor in the air compared

to the maximum amount the air cloud hold at that temperature. Psychrometer: An instrument used to measure relative humidity,

consisting of a wet-bulb thermometer and a dry-bulb thermometer. Condensation: The process by which molecules of water vapoar in the

air become liquid water. Dew Point: The temperature in which condensation begins. Cumulus: Clouds that form least than 2 kilometers above the ground

and look like fluffy, rounded piles of cotton. Stratus: Clouds that form in layers. Cirrus: Wispy, feathery clouds made mostly of ice crystals that form at

high levels, above about 6 kilometers.

Precipitation

Rain, sleet, freezing rain, hail and snow Rain is measured with a rain gauge Scientists have used cloud seeding to

produce rain and to clear fog from airports

Key Terms

Precipitation: Any form of water that falls from clouds and reaches Earth’s surface.

Rain Gauge: An instrument used to measure the amount of precipitation, consisting of an open-ended can topped by a collecting funnel and having a collecting tube and measuring scale inside.

Drought: Long periods of low precipitation.