Geography 2152F/G Lecture 5: Lec5 - Earth's Energy Balance
20 Feb 2019
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Geography of Hazards 2152B
Lecture 5 – Earth’s Energy Balance
Earth’s Energy Balance
• There is an equilibrium between incoming radiation and outgoing radiation.
• Earth intercepts only a small portion of the sun’s radiation
• The Sun’s energy drives the hydrologic cycle and all-weather phenomena on Earth.
• Nearly all of the energy available at earth’s surface comes from the sun
• The sun’s radiation comes down and then 30% bounces off the atmosphere immediately
• 25% is absorbed (for example ozone absorbs) while the rest goes directly to earth
• There should be a balance of stuff coming in and out – there is climate change occurring because not all
the earth’s heat is able to escape so it is imbalanced right now and earth’s temperature are increasing
The Atmosphere
• It is composed of nitrogen (78%) and oxygen (21%).
• The remaining 1% consists of water vapor, carbon dioxide and other ‘trace’ gases
• Water vapor in the atmosphere can result in cloud development and the formation of precipitation.
• Water vapor comes from evaporation from the oceans
• The oceans and lake, when the sun hits them then water becomes vapor through evaporation
Geography of Hazards 2152B
Structure of the Atmosphere
• All weather (i.e. clouds and precipitation) is confined to the
troposphere.
• The ozone layer (25 km above the surface) protects us from
the Suns harmful UV rays; it is found in the stratosphere
• We live in the trophosphere, above us is the stratosphere
• Temperature warms as we go through the stratosphere,
reason is because the ozone layer is there which warms the
stratosphere layer
• Closer up is the thermosphere
• Clouds are confined to the trophosphere and the weather
• Mainly about our protection against UV rays and against skin
cancer
Clouds
Cloud names generally contain a prefix and a suffix.
The prefix describes the height of the cloud; the suffix describes its appearance.
Prefixes: Suffixes:
High cloud: cirro- Puffy: -cumulus
Mid-level cloud: alto- Flat: -stratus
Low cloud: strato-
None of these clouds produce precipitation
Ex: A high puffy cloud is called a cirrocumulus cloud
Clouds
• Clouds that produce precipitation contain “nimb” in their name.
• Cumulonimbus → A cloud that produces lightning, thunder, and heavy rain.
• Nimbostratus → A cloud that produces prolonged precipitation
• Thunderstorm clouds, only clouds that produce thunder, lightning and tornadoes
• Not well developed in height, they are often in the spring and winter with rain and snow
Fronts
• A “front” marks the boundary between two air masses
• The name of the front describes the type of air behind that front.
• At a cold front, dense cold air undercuts warm air
• At a warm front, the less dense warm air overrides cold air.
• Warm front is much more gentle and don’t get thunderstorms
• The cold front has cold air BEHIND it
• Warm front has WARM air,
• Warm air is forced up when the cold air is coming in, this is where clouds form because the air is rising
really quickly
• When warm air is coming in, it is gentle precipitation as it pushes the cold air away
Geography of Hazards 2152B
Thunderstorms
At any moment, there are approximately 2000 thunderstorms occurring on Earth.
Thunderstorm development requires:
• An unstable environment (a steep vertical temperature gradient)
• Water vapor
• Rising air (or a lifting mechanism, e.g. a front)
• Thunderstorms = violently rising air where there is a great different in temperature
Thunderstorm Development
• They develop in three stages: cumulus, mature, dissipative
• Most storms pass through all three stages in 1 hour
•
Hail
• It is formed during thunderstorms in very tall clouds.
• Updrafts in the cloud repeatedly force a water droplet upward.
• The droplet develops a ring of ice around It each time it enters the cold part of the cloud.
Document Summary
There is an equilibrium between incoming radiation and outgoing radiation. Earth intercepts only a small portion of the sun"s radiation. The sun"s energy drives the hydrologic cycle and all-weather phenomena on earth: nearly all of the energy available at earth"s surface comes from the sun. The sun"s radiation comes down and then 30% bounces off the atmosphere immediately. 25% is absorbed (for example ozone absorbs) while the rest goes directly to earth. There should be a balance of stuff coming in and out there is climate change occurring because not all the earth"s heat is able to escape so it is imbalanced right now and earth"s temperature are increasing. It is composed of nitrogen (78%) and oxygen (21%). The remaining 1% consists of water vapor, carbon dioxide and other trace" gases: water vapor in the atmosphere can result in cloud development and the formation of precipitation, water vapor comes from evaporation from the oceans.
