Weather Factors Chapter 16

What does the movement of heat in the atmosphere cause?

The movement of heat in the atmosphere causes temperatures to change, rain to fall, and winds to blow.

Energy from the Sun Most of the energy from the sun travels to Earth in the form of visible light and infrared radiation. A small amount arrives as ultraviolet radiation. Most of the energy from the sun travels to Earth in the form of visible light and infrared radiation. A small amount arrives as ultraviolet radiation.

Energy in the Atmosphere Some sunlight is absorbed or reflected by the atmosphere before it can reach the surface. The rest passes through the atmosphere to the surface. Some sunlight is absorbed or reflected by the atmosphere before it can reach the surface. The rest passes through the atmosphere to the surface. –Absorbed Water vapor and other gases absorb infrared radiation. Water vapor and other gases absorb infrared radiation. Ozone layer absorbs ultraviolet rays. Ozone layer absorbs ultraviolet rays. Clouds, dust, and other gases also absorb energy. Clouds, dust, and other gases also absorb energy. –Reflected Dust particles and gases in the atmosphere reflect light in all directions, a process called scattering. Dust particles and gases in the atmosphere reflect light in all directions, a process called scattering.

Energy at Earth’s Surface When Earth’s surface is heated, it radiates most of the energy back into the atmosphere as infrared radiation. When Earth’s surface is heated, it radiates most of the energy back into the atmosphere as infrared radiation. The process by which gases hold heat in the air is called the greenhouse effect. The process by which gases hold heat in the air is called the greenhouse effect.

How are thermal energy and temperature related?

Thermal energy and temperature are related because temperature is the average amount of energy of motion of each particle of a substance whereas thermal energy is the total energy in a substance.

How Heat is Transferred Heat is transferred through Heat is transferred through –Radiation –Conduction – the direct transfer of heat from one substance to another substance that it is touching. –Convection – the transfer of heat by the movement of a fluid. Radiation, conduction, and convection all work together to heat the troposphere. Radiation, conduction, and convection all work together to heat the troposphere.

Winds

What is Wind? A wind is the horizontal movement of air form an area of high pressure to an area of lower pressure. A wind is the horizontal movement of air form an area of high pressure to an area of lower pressure. Winds are caused by differences in air pressure. Winds are caused by differences in air pressure. –Winds are measured using an anemometer. –Wind–Chill factor is the increased cooling a wind can cause.

Local Winds Local winds are winds that blow over short distances. Local winds are winds that blow over short distances. Local winds are caused by the unequal heating of Earth’s surface within a small area. Local winds are caused by the unequal heating of Earth’s surface within a small area. –A sea breeze or a lake breeze is a local wind that blows from an ocean or lake. –A land breeze is a flow of air from land to a body of water.

Global Winds Global winds are winds that blow steadily from specific directions over long distances. Global winds are winds that blow steadily from specific directions over long distances. –Global Convection Currents –The Coriolis Effect

Global Wind Belts The major global wind belts are the trade winds, the polar easterlies, and the prevailing westerlies. The major global wind belts are the trade winds, the polar easterlies, and the prevailing westerlies. –Doldrums –Horse latitudes –Trade winds –Prevailing westerlies –Polar easterlies –Jet Streams

Water in the Atmosphere

Humidity Humidity is the measure of the amount of water vapor in the air. Humidity is the measure of the amount of water vapor in the air. –Relative humidity is the percentage of water vapor that is actually in the air compared to the maximum amount of water vapor the air can hold at a particular temperature. –Relative humidity can be measured with an instrument called a psychrometer.

How Clouds Form Clouds from when water vapor in the air condenses to form liquid water or ice crystals. Clouds from when water vapor in the air condenses to form liquid water or ice crystals. Molecules of water vapor in the air become liquid water in the process of condensation. Molecules of water vapor in the air become liquid water in the process of condensation. –The temperature at which condensation begins is called the dew point.

Types of Clouds Scientists classify clouds into three main types based on their shape Scientists classify clouds into three main types based on their shape –Cirrus Clouds – wispy, feathery clouds –Cumulus Clouds – fluffy, founded piles of cotton. –Stratus Clouds – clouds that form in flat layers Autocumulus and autostratus refer to high clouds. Autocumulus and autostratus refer to high clouds. Clouds that form near the ground are called fog. Clouds that form near the ground are called fog.

Precipitation

Types of Precipitation –Rain –Sleet –Freezing Rain –Snow –Hail Modifying Precipitation Modifying Precipitation –Droughts are long periods of unusually low precipitation. –Cloud seeding is one method used to modify precipitation.

Measuring Precipitation Scientists measure precipitation with various instruments including rain gauges and measuring sticks. Scientists measure precipitation with various instruments including rain gauges and measuring sticks.