Earth Science Chapter 9

Chapter 9 Weather and Climate

Lesson 1 What Factors Affect Climate? Climate is the normal pattern of weather in an area over many years. Climate in an area is affected by: Earth’s shape Tilt of its axis Geographic features

Uneven Heating The Sun’s rays strike Earth at different angles. The closer the angle to the Sun, the warmer the climate in that area. Example: The Equator

Major Climate Zones Earth has three Major Climate Zones Tropical, Temperate, and Polar Their differences are: Average temperature Amount of precipitation (rain, sleet, snow, or hail)

Tropical Climate Zones Occur at the Equator, or areas just North and South of it Warm temperatures all year round Often very rainy

Temperate Climate Zones North and South of the tropics Warm summers, with rain as precipitation. Winter is cool- very cold, and precipitation falls as snow We live in a temperate climate Have 4 seasons

Polar Climates Located close to Earth’s North Pole and South Pole. Very cold year round. Most precipitation falls as snow.

Land and Sea Breezes Unequal heating of land and water causes Land and Sea Breezes. Sea Breezes- flow from the WATER towards the land. Land Breezes- flows from the LAND toward the water.

Mountain Effect Mountains can affect precipitation. Most air flows up the windward side of a mountain. The windward side receives more precipitation than the leeward side.

Ocean and Climates Ocean Currents Caused by the wind pushing against the ocean’s surface, moving streams of water. Warm ocean currents move warm water away from the equator toward the poles. Cold ocean currents move cold water away from the poles and toward the equator.

El Niño The name given to a periodic change in the direction of warm ocean currents across the Pacific Ocean. Occurs every 5-7 years Can cause change in climate around the world

Lesson 2 How Are Weather Forecasts Made? Earth’s atmosphere is a mixture of gases that surrounds the planet. Changes in the air causes changes in weather.

Structure of the Atmosphere Divided into four main layers. Troposphere- Closest to Earth Where almost all weather occurs Thinnest layer Contains 75% of gases that make up the atmosphere.

Stratosphere Lies above the Troposphere Air is much colder and drier Contains most of the Planet’s Ozone layer Absorbs radiation from the Sun

Mesosphere Lies above Stratosphere Coldest layer of Earth’s atmosphere

Thermosphere Thin layer of Earth’s atmosphere First layer struck by sunlight

Air Masses An AIR MASS is a huge volume of air that affects weather in a certain area Can be dry OR humid, and warm OR cold, depending on where it forms

Fronts A front is a boundary between two air masses When two DIFFERENT air masses meet, they create a front. Warm fronts form when warm air moves into an area, causes light rains Cold fronts form when cold air moves into an area, usually has heavy rains

Observing Weather Weather is the overall condition of the atmosphere at a given time and place. Meteorologists are scientists who study weather. Weather maps display atmospheric conditions.

RADAR Radar is a useful tool for observing and forecasting weather Can be used to create an image of a storm. Size, direction, amount of precipitation and speed of the storm can be determined

Other Weather Instruments Satellites orbiting the Earth measure data in the atmosphere and relay it to Earth Thermometers- measure temperature in Celsius or Fahrenheit Anemometers- measure wind speed Barometers- measure air pressure Rain Gauges- collect and measure amount of rain, snow, sleet or hail. Weather Vane- indicates the direction the wind is blowing