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Weather and Climate

Geography 12 Princess Margaret Secondary

JB Mahli

on 20 February 2012

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Transcript of Weather and Climate

Weather and Climate Troposphere is the turbulent layer of the atmosphere
in which all aspects of weather are found.
- clouds
- rain
- surface winds
- hurricanes
- tornadoes
This layer affects us on a daily basis Temperature at the top of the Troposphere drops to about -56 degrees Celsius. BUT in the
Tropopause the temperature actually increases!!! Why? Because of the effect of the ozone layer. The Stratosphere lacks the turbulence of the
troposphere due to it's reduced density and
weather conditions in this layer remain constant The Mesosphere is the third layer of the atmosphere
and here temperatures drop again as UV radiation is
allowed to pass through without being absorbed.
Temperatures drop to -100 degrees Celsius near the top
Meteors entering the earth's atmosphere burn up here! The Thermosphere is the thickest layer and here
temperatures rise again as air molecules are few
...allowing the incoming solar radiation to rapidly
heat the thin air.
Temperature depends on solar activity
Estimated as high as 3000 degrees Celcius The Exosphere is the end of our atmosphere. There are
so few air molecules it is nearly a vaccuum. When your
parents are angry with you they probably want to send
you to the Exosphere :) Air Masses Fronts
Polar Front: Frigid, arctic air that moves south from the north pole in winter months
Warm Front: Warm air mass
Cold Front: Cold air mass
Stationary Front: Warm and Cold air boundary that remains in one place
Occluded Front: Cold front overruns a warm front mixing the air from the two Air mass classifications
place of origin
originate over land or water
stable or unstable air Air masses of North America
Continental Polar
Maritime Polar
Maritime Tropical
Continental Tropical Global Winds Winds are named from the direction FROM which the blow...not the direction they are going.
Ex. winds blowing from the Pacific toward the coast of North America are called westerly. The Water Cycle Continual cycle and movement of water
from the oceans into the atmosphere Moist air rises
Water vapour condenses to form clouds Humidity - amount of water vapour in the air
Absolute humidity - amount of water vapour present in a body of air
Relative humidity - Percentage of water vapour in the air
Dew Point - Relative humidity reaches 100% Clouds Types of Precipitation Clouds are condensed water vapour
and consist of water droplets or ice crystals Cirrus Stratus Cumulus Cirrus, Cirrostratus, Cirrocumulus High Clouds 7,000 to 13,000 metres Mostly ice crystals, no precipitation Middle Clouds Altostratus, Altocumulus 2,000 to 7,000 metres Low Clouds Stratocumulus, Stratus, Nimbostratus 0 - 2,000 metres Stratus may produce steady drizzle
Nimbostratus produce steady, prolonged precipitation Cumulus Cumulonimbus Vertical Clouds Rising air current produce a cauliflower appearance...extreme heating is needed Violent, circulating air currents, which produce baseball size hail. Thunder and lightening also commonly associated. Flat-topped, anvil shaped and rainfall is sudden, very heavy and short-lived. 1. Orographic Precipitation 2. Frontal Precipitation
Warm Front
Cold Front 3. Convection Precipitation The Weather Map Measurement of local weather conditions.
Includes temperature, cloud cover, wind speed and direction, and change in air pressure. Average sea-level pressure on earth is 1013.2 mbs or 101.3 kPa High Pressure Low Pressure Anticyclones Cyclones (depressions) 217 +22 3 -3 To determine the correct air pressure at a weather
station, one must add either a 9 or a 10 in front of
the numbers appearing on the weather station.
lowest pressure is 95 kPa (eye of a hurricane)
highest pressure is 104 kPa (Siberia)
If the first number is less than 5 then add a 10
If the first number is 5 or more then add a 9 The arrow head (in the circle) points
in the direction that the wind is blowing FROM! Northwest Wind Weather Disturbances Active weather systems develop along fronts where two air masses meet
For example: Polar air mass colliding with Continental Tropical air mass Violent Storms Hurricanes Tornadoes Tropical Cyclones
Require warm air and a large body of warm water
Ideal in the warm, moist, equatorial doldrums
Atlantic hurricanes begin its life off the northwest coast of Africa
Why?? Abundance of warm air and warm water
If there is enough warm water and warm air, then this low pressure disturbance will develop into a hurricane Most violent of all storms...winds reach 500 km/h
Air pressure in a tornado is much lower than the surrounding air so air rushes into the counter-clockwise rotating funnel of whirling winds
Cumulonimbus cloud forms and produces hail and extremely heavy localized rainfall Climate Climate Controls 1. Latitude
As latitude increases, the average temperature decreases and the annual temperature range increases

2. Distribution of land and water masses
Water heats slowly but retains heat for a long time
Land heats quickly but cools quickly
Climates closer to water tend to have milder winters, cool summers, and farmore precipitation...like us!
Areas far from water have great temperature ranges and much drier coastal regions

3. Ocean currents
Plays a major factor in influencing the temperature and precipitation of adjacent land.
Some ocean currents are able to transfer heat from the source of the current to far away regions. Ex. Gulf Stream

4. Winds
If winds orgininate over ocean, the air will be moist and cool and much rain
If winds originate over land they carry far less moisture and can even result in desert conditions

5. Mountain barriers
Act as a blockade to advancing weather from reaching the leeward side of the mountains.
The higher the mountain range the more likelyhood that desert conditions will appear on the leeward side of the mountains.

6. Altitude
The higher the altitude the lower the air temperature

7. High and Low pressure belts
High pressure is associated with stable, sunny weather (20-30 degrees - deserts)
Low pressure is associated with unstable, rainy weather (equatorial regions) Climates of the world Tropical Climates Dry Climates Temperate and subtropical climates Cold Climates Equatorial (Tropical Wet) Tropical Wet-Dry Constant low pressure
High temperatures
Rain all year (Convection)
Ex. Singapore, Singapore Borders equatorial climate
Distinct wet and dry season
Temperatures high all year
Summer months causes causes convection due
Ex. San Salvador, El Salvador Tropical Monsoon Influenced by a reversal of winds, which for six months, blow from land to sea creating drought conditions.
When the winds reverse, they blow from ocean to land, resulting in heavy precipitation for six months.
Temperature remains the same year round
Ex. Mumbai, India Tropical Desert (Hot Desert) Located in the high pressure belts and along west coast of continents
Temperature warm all year
Average precipitation is less than 50mm
Ex. Cairo, Egypt Tropical Steppe (Hot Steppe) Temperature same as Tropical Desert
Increase in precipitation to 200-400 mm
Steppe is transitional climate between wetter areas and dry desert
Ex. Lahore, Pakistan Temperate Steppe Termperature drops to below zero in the winter but summers remain hot
Precipitation is considerably higher
Ex. Medicine Hat, Canada Far from the equator
Temperatures are far cooler than tropical deserts
Located in the heart of continents and in the rain shadow on the leeward sides of great mountain ranges
Ex. Temperate Desert Mediterranean Climate West Coast Marine Humid Subtropical Hot summers (drought conditions
Mild Winters (min 6 deg)
Ex, Sacramento, USA Influenced by offshore winds
Precipitation is year round
Small temperature range
Ex. Vancouver, BC Found in eastern coastal regions
Moist climate with precipitation year round...wetter summers
Hot summers cool winters (min 10 deg)
Ex. New Orleans, USA and Shanghai, China Humid Continental Sub Arctic Northern regions of North America and Asia
Lack of ocean influence results in huge temperature range
Bitterly cold winters but warm/short summers
Moderate annual precipitation
Not found in the southern hemisphere...continents too small
Ex. Ottawa, Ontario Found north of Humid Continental
Truly a cold climate
Low precipitation because air is too cold to reach dew point
Ex. Inuvik, Canada
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