Weather and Climate

Weather Patterns

Weather Weather is the state that the atmosphere is in during a short period of time in a small location Time: minutes, hours, days Location: towns and counties

Weather Day-to-day weather is the result of the movement and interactions of air masses in the Earth’s atmosphere. An air mass is a large body of air that has fairly uniform physical properties, such as… Temperature Moisture content

Air masses Maritime polar originate over northern Pacific & Atlantic oceans. They are cool and moist w/heavy precipitation Continental polar form over Canada & bring cold dry air. Maritime Tropical form over the Gulf of Mexico & bring warm, moist air with fog or rain. Continental tropical originate over the southwest and Mexico & bring dry, hot air.

When Air Masses Meet Air masses don’t stay where they form. They move with the circulation of air (convection currents) throughout the world. These air masses can easily collide!

Fronts A sharply defined boundary that forms when two unlike air masses meet is called a front. Clouds and precipitation often accompany fronts. There are four types of fronts: Cold fronts Warm fronts Stationary fronts Occluded fronts

Cold Fronts A cold front occurs when a cold air mass overtakes a warm air mass. Happens in North America when a cold continental polar air mass collides with a maritime tropical air mass from the Gulf of Mexico. A cold front causes strong winds, thunderstorms, and great precipitation, but only for a short period of time. After the front passes, the cold air mass settles in, the skies clear and the temperature drops.

Warm Fronts A warm front occurs when a warm air mass overtakes a cold air mass. Warm fronts cause steady rain. When it passes, skies are mostly clear and warm air settles in.

Stationary fronts Sometimes when two air masses converge, neither air mass overruns the other. Instead, the two unlike air masses from a boundary that either stays where it is or moves slowly. This unmoving boundary is called a stationary front. A stationary front can cause steady rain for days.

Occluded Fronts An occluded front can form when warm air is caught between two cooler air masses. This trapped warm air rises and usually causes cloudy skies and precipitation.

Storms Storms feature strong winds and heavy precipitation. The major types of storms are… Thunderstorms Tornadoes Tropical storms Hurricanes

Thunderstorms A thunderstorm is a small weather system that includes thunder and lightning. It is accompanied by strong winds and heavy rain or hail. Thunderstorms form when columns of air rise within a cumulonimbus cloud. They often are a result of a cold front.

Lightning Lightning is a sudden electrical charge in the atmosphere. It occurs when the bottom of storm clouds become negative, making the ground positive, which provides a path for electrical charge to flow.

Thunder Thunder is the sound produced by rapidly expanding air along the path of a lightning discharge. Lightning heats the air around it up to 3000°C. This heated air expands explosively, producing sound waves you hear as thunder. Lightning and thunder occur at the same time, but since light waves travel faster than sound, you see the lightning before you hear the sound.

Tornadoes A tornado (twister) is a small but intense windstorm that takes the form of a rotating column of air that touches the ground. Tornadoes form when a vertical cylinder of rotating air develops in a thunderstorm. They very often form at the edge of a cold front or where winds converge in a thunderstorm.

Tropical Storms Cyclones (areas of low pressure where winds turn) occur very often in middle latitudes and tropics. They can develop into a tropical storm (a cyclone with winds up to 75 mph) or a hurricane (a cyclone with winds at least 75 mph.)

U.S. Weather Map

Climate

Climate Climate is the long-term weather conditions of a place or region. It is the description of the pattern of weather over many years over many states or countries

Factors Affecting Climate Latitude- Distance (north or south) from the Earth’s equator Latitude determines how much solar heat an area receives over the seasons. Closer to the equator = warmer climate Farther from the equator = cooler climate

Factors Affecting Climate Distance from large bodies of water Air above large bodies of water vary much less in temperature, so coastal areas typically have less temperature variation over a year than regions at the same latitude within continents. Being next to water usually increases precipitation Being next to water increases wind currents

Factors Affecting Climate Ocean currents- The temperature of coastal regions are influenced by nearby ocean currents. Hot water rises and cold water sinks

Factors Affecting Climate Elevation- Height above sea level Higher elevation = cooler temperatures

Factors Affecting Climate Wind Currents Warm air rises and cold air sinks The direction global winds blow can either bring in precipitation (from areas like an ocean), or take it away (to ocean).

Factors Affecting Climate Terrain- physical properties of land (mountains, valleys, etc) As moist air rises over mountains, the water vapor condenses and rain or snow falls on one side of the mountain. The opposite side receives the cooler dense dry air that sinks.

Classifying Climates The Earth is divided into six major climate groups: Tropical Temperate marine temperature Temperate continental Polar Dry precipitation Highlands elevation Based on…

Climate Regions