Atmosphere Review

Earth’s atmosphere is the layer of gases that surrounds the planet and makes conditions on Earth suitable for living things. Nitrogen (78%) and oxygen (21%) are the most common gases in the atmosphere. They are found in all the layers of the atmosphere. Air pressure increases as you travel from the exosphere to the troposphere. Weather only occurs in the troposphere. Ozone is a form of oxygen that is found in the stratosphere. It absorbs energy from the sun and warms the air. Water vapor and carbon dioxide are only found in the troposphere. They are the gasses necessary for weather to occur. 

Solar energy (the sun) is the driving energy source for heating Earth and for the circulation of the Earth’s atmosphere.
Some of the Sun’s energy coming through the atmosphere is reflected or absorbed by gases and/or clouds in the atmosphere.
The land heats up and releases its heat fairly quickly, but water needs to absorb lots of solar energy to warm up. This property of water allows it to warm more slowly but also to release heat more slowly. It is water on Earth that helps regulate the temperature of Earth’s atmosphere.
Solar energy that is absorbed by Earth’s land and water surfaces is changed to heat that moves/radiates back into the atmosphere (troposphere) where the heat cannot be transmitted through the atmosphere so it is trapped. This process is knows as the Greenhouse Effect. 

Evaporation/Transpiration: Water enters the atmosphere as water vapor through evaporation and transpiration (plants releasing water vapor). Condensation: Condensation happens in the atmosphere as water vapor changes into water droplets. Condensation causes clouds to form. Dew forms when water vapor condenses onto a surface. Frost forms when water vapor changes from gas directly to ice crystals on a surface where the temperature is freezing or below. Precipitation: Water droplets fall from the clouds which were formed through condensation. The condensed water droplets fall as various forms of precipitation such as rain, snow, freezing rain, sleet, or hail, depending on the weather conditions. Temperatures in the clouds and atmosphere create the different forms of precipitation. Run-off: Precipitation falling on land surfaces always attempts to move back toward sea level. If the ground is not porus and the water can’t be absorbed, the water is called surface-water flow. Surfacewater flow also happens when it rains too fast for the ground to absorb the water. Groundwater flow occurs when the surface is porus and allows the water to be absorbed into the ground. There is lots of space in the soil to hold the water. 

Cumulus clouds are formed at medium or low elevation. They are puffy with flat bottoms. When they are white they often signal fair weather. When they are darker they may signal rain or thunderstorms. Cirrus clouds form at high elevations. They are wispy clouds usually consisting of ice crystals. They signal fair weather and may also signal the approaching warm front. Stratus clouds form at medium or low elevation. They spread out layer upon layer covering a large area. As stratus clouds thicken, precipitation usually occurs over that area. Many clouds are combinations of the three basic shapes. Prefixes and suffixes are added to name some of these clouds. -nimbus means rain, examples are cumulonimbus or nimbostratus. A cumulonimbus cloud (a thunderhead) is often part of a thunderstorm and may accompany a cold front -alto indicates clouds that form at 2-6 kilometers up in the atmosphere, examples are altocumulus or altostratus Alto means “found in the middle layer” -Fog is clouds that form at or near the ground. 

Air masses are huge bodies of air, they are formed over water (humid) or land (dry) in tropical (warm) or polar (cold) regions. We talk about the movement of air masses, so the temperature and humidity conditions within the air masses are important because weather events happen when air masses move. Fronts are air masses that move and collide with each other, fronts form at the boundaries between the air masses. Depending upon the air masses involved, a warm front, cold front, stationary front, or occluded front can develop.

High Pressure Systems and Low Pressure Systems form when warm air rising or cold air sinking combined with the spinning of Earth causes the air to spin forming high and low pressure regions. 

Satellite Images are used for seeing cloud patterns and movement (hurricane clouds and movement). Radar images can be use to detect cloud cover, rainfall or storm location, intensity and movement, as well as the potential for severe weather and even tornadoes or hurricanes. Warm air near the surface of the earth rises and then cools; this is a convection current. There are three atmospheric convection areas in the northern hemisphere and three in the southern hemisphere. The areas in the northern hemisphere are: o Tropical Convection Region – begins at the equator and extends about 30 degrees north latitude o Temperate Region – extends from about 30 degrees to about 60 degrees north latitude o Polar Regions – extends from about 60 degrees to the north pole (which is 90 degrees north latitude) Convection on a global scale causes global winds which move weather systems and surface ocean currents. o Global Wind Belts – weather systems move in certain directions because of the spinning of the earth o Land Breezes (blow from the land to sea), Sea Breezes (blow from the sea to the land) – these are local winds o Surface Currents of Earth’s oceans circulate warm and cold ocean waters in convection patterns also influence weather and climates of nearby landmasses o Gulf Stream is warm current water that effects the eastern Atlantic coastline Climate Zones (tropical, temperate, and polar) exist because of unequal heating of Earth. Since temperature is a major factor in climate zones, climate is related to: convection regions, temperature differences, and warm and cold surface ocean currents. Global Winds are found in each convection region. The winds appear to curve due to the spinning of the earth (Coriollis effect). Trade Winds blow from east to west in the tropical regions moving the warm tropical air in that climate zone o Prevailing Westerly Winds blow from west to east in the temperate region. o Changing seasons effect the temperate zone. This causes weather systems in the US to move west to east. o Tropical Weather Systems like hurricanes move in the direction of the trade winds (east to west). o The Polar Winds blow northeast to west moving cold polar air from the poles to the west. The Jet Stream is a fast moving ribbon of air that moves around the globe of Earth. It moves from west to east in the Northern Hemisphere (in the United States). It dips and bends and constantly changes position. Air masses and weather systems in its path are moved along by the fast moving air. The polar jet stream can bring cold air from the north. The subtropical jet stream can bring warm tropical conditions from the south.