Climate The average weather conditions for an area over a long period of time.

Temperature and Precipitation Used to define climates Daily averages: to estimate the average daily temperature/precipitation, add the high and low of the day and divide by 2. Monthly averages: to estimate average monthly temperature/precipitation add all the daily averages and divide by the number of days in the month. Yearly averages: to estimate the average yearly temperature/precipitation add up all 12 monthly averages and divide 12. Yearly range: the difference between the highest and lowest monthly averages.

Latitude Influences both temperature and precipitation Different latitudes receive different amounts of solar energy. Solar energy determines the temperature and wind patterns of an area. The higher the latitude of an area, the smaller the amount of solar energy received by that area.

Seasons Because the Earth’s axis is tilted, the angle at which the sun’s rays hit the earth changes as Earth orbits the sun. During winter, the northern hemisphere is tilted away from the sun, and areas at the higher northern latitudes face the sun for less time than during the summer; the days are shorter and the temperatures are lower during the winter.

Seasons

The amount of precipitation generally decreases as latitude increases. Air rises, cools, condenses Air sinks, warms, dries

Heat Absorption and Release Different areas absorb and release heat differently Land heats faster than water and can reach higher temperatures in the same amount of time.

El Nino – Southern oscillation “ENSO” A cycle of changing wind and water-current patterns in the Pacific Ocean, every 3-10 years. El Nino is the warm water phase of ENSO, causes surface water temperatures along the west coast of South America to be warmer. During El Nino, typhoons, cyclones, and floods may occur in Pacific regions and southeast United States. Other areas may have droughts. The southeast U.S. experiences cooler and wetter winters. La Nina is the cooler water phase of ENSO, causes surface water temperatures along the west coast of North America to be cooler.

Seasonal Winds (Monsoons) Temperature differences between the land and the oceans sometimes cause seasonal wind shifts. During the summer, the land warms more quickly than the oceans; the warm air rises and is replaced by cool air from the ocean. The wind moves toward the land, which leads heavy rains and flooding. During the winter, the land loses heat more quickly than the ocean; the cool air flows away from the land; the wind moves seaward – dry winds and drought.

Topography Surface features of the land influence the flow of air. Elevation Rain shadows Temperature decreases with elevation. When a moving air mass encounters a mountain, the air mass rises, cools, and loses most of its moisture. As a result, it precipitates on one side of the mountain; And the other side is usually warm and dry. Warm, dry winds that flow down the mountain Foehn (Alps) Chinooks (Rockies)

Andes Mountains

Himalayan Mountains

3 Major Climatic Zones Tropical Middle-latitudes (temperate) Polar

Microclimates The climate of a small area

Climate Change Climatologists study and compare past and present climates: 1000’s of weather stations (past and current data) Fossils of plants and animals (environmental clues) Ice cores from polar icecaps (gas composition) Tree rings (wet/dry years) Sea-floor sediments (oxygen levels tell us about temperature) Causes of climate change: Plate tectonics (movement of continents) Orbital changes in shape/tilt Human activity (CO2 increase) Volcanic activity