Section 1: Atmosphere and Climate Change Chapter 13 Section 1: Atmosphere and Climate Change

Terms Weather: state of the atmosphere at a particular place at a particular moment. Climate: long-term prevailing weather conditions at a particular place based upon records taken.

What Factors Determine Climate? Latitude Atmospheric circulation patterns Oceanic Circulation patterns Local geography of an area Solar activity Volcanic Activity Distance from the equator

Latitude Distance from the equator measured in degrees north or south of the equator. Low latitudes: temperatures high year-round. No summers or winters. High latitudes: yearly temperature range is larger.

Atmospheric Circulation Cold air sinks As cold air sinks, it compresses and warms. Warm air rises, expands and cools.

Solar energy heats the ground, which warms the air above it. This warm air rises, and cooler air moves in to replace it. (WIND) Circulation pattern determines precipitation pattern. Areas near equator are warmer, warm air holds more water. As water cools, it cannot hold as much water—this leads to rain.

Global Circulation Patterns Cool air over the equator is forced toward the poles. Cold, dry air descends at the poles, which are essentially very cold deserts. Coriolis Effect – air defected from its path due to earth’s rotation http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.mov

Three Prevailing Winds Due to Coriolis Effect Polar easterlies Westerlies Trade Winds

Prevailing Winds Prevailing winds: winds that blow predominantly in one direction throughout the year. Trade winds: Blow from the northeast in the Northern hemisphere and the southeast in the Southern hemisphere. Near the equator. Westerly's: northwest winds in Northern hemisphere, and southwest winds in the Southern hemisphere. 30-60o latitude Easterlies: cold dry air – cold deserts

Oceanic Circulation Patterns Surface currents affect the climate in many parts of the world. El Niňo: Pacific ocean is warmer than usual. Causes increased rainfall in some areas and droughts in others. La Niňa: (opposite) Pacific is cooler than usual.

Topography Mountains trap clouds, which can cause rain on one side and dry air and climate on the other.

Other Influences on Earth’s Climate Sun: Increased UV rays = increased ozone = warmer atmosphere. Volcanic eruptions: sulfur dioxide released reflects sunlight and causes global temp. to decrease.

Seasonal Changes in Climate Seasons change as a result of the earth’s tilt on its axis. Northern hemisphere tilts toward sun in summer and away from it during winter.