Lesson 3 Flashcards
What is meant by the term weather
- it is a hour to hour and day to day variability in atmospheric conditions
- > this includes precipitatation, humidity, air pressure and wind at any specific location
- > these conditions can change rapidly
What is meant by the term climate
- climate is the long-term average of weather and its extremes
- > more predictable than weather
What are mountain climates characterized by
-they are characterized by extremes in temperatures, precipitation, wind and radiation
What are the three primary forces determining and regulating mountain climates
1) Latitude or distance from the equator
2) Elevation or height above sea level
3) Continentality
- >proximity or distance to large water bodies such as oceans
Why are climates warmer near the equator
- because the Sun’s ray hit the Earth directly
- > concentrating solar radiation
- > in contrast, at higher latitudes, the Sun’s rays hit the Earth at an angle casing the same solar radiation to be spread over a larger area
What is seasonality
-the control of temperature fluctuation is controlled through latitude
Is the Earth closer to the Sun during the winter and further away during the summer in the northern hemisphere
-yes
Why is there greater seasonality at higher latitudes
1) The tilt of the earth on its axis
- >the Earth is tilted on its axis at an angle of 23.5 degrees
- >so as Earth completes its annual orbit around the Sun
- >the Northern and Southern Hemispheres are angled towards the Sun at opposite times of the year
- >whichever hemisphere is tilted towards the Sun receives solar radiation most directly and has more hours of daylight(southern hemisphere)
2) Revolution of the Earth around the Sun
3) greater variation in solar radiation
Is seasonality weaker at the equator than the higher latitudes
-yes
What is the exception to the rule that temperature decreases with increasing latitude
- during the summer in the northern hemisphere, solar radiation strikes the Earth most directly near the Tropic of Cancer around the latitude of 23.5 degrees North
- > here temperatures are higher during the summer than in the tropics near the equator
- opposite patterns occur during the the summer in the Southerh Hemispher
- > where the temperatures are often warmers near the Tropic of Capricorn
What is air temperature
- how hot or cold the air is
- >hot air is less dense than cool air
What is atmospheric pressure
- it is the downward force of air in the atmosphere
- >caused by gravity pulling molecules of air towards the air
How is wind generated
-by air moving along pressure gradients from areas of high to low pressure
What is the intertropical convergence zone
- near the equator, high temperatures create an area of low atmospheric pressure
- > this is the intertropical convergence zone
What are circulation cells
- they are belts that encircle the Earth in which prevailing winds occur
- > if the Earth did not rotate, there would only be two circulation cells
- > one in each hemisphere
- > but with the rotation of the Earth on its axis, there is three circulation cells within each hemisphere
Describe the Hadley cells
- rising air near the equator flowes toward the poles
- > 10-15 kilometers above the surface
- > it then descends in the subtropics before returning to the equator closer to the surface
What is the Coriolis effect
- the rotation of the Earth deflects winds so they do not flow directly north and south
- > it provides an explanation for why object curve on Earth and do not move in a straight line
Which direction does the Earth rotate in
-it rotates from east to west
Describe the winds in the three circulation cells
Hadley
- > trade winds
- > blow west and towards the equator
Midlatitudes
->westerlies blow from the west towards the east and upwards towards the poles
High Latitudes
->the polar Easterlies blow from the east towards the west and towards the equator
What is low atmospheric pressure associated with
- since it is rising of moist, warm air
- >low atmospheric pressure is associated with cloudiness and high levels of precipitation
What is high atmospheric pressure associated with
- in areas with high atmospheric pressure
- >there are clear skies and dry conditions
Are Himalayas in arid zone
- yes they are at 30 degree latitude
- > they are more dry than the tropical mountains of Mount Kilimanjaro and Mount Kinabalu
- > these mountains are at low pressure zones near the equator and are more tropical
Why are temperatures lower at higher elevations
- temperature decreases with elevation
- > as elevation increases, atmospheric pressure decreases
- > causing rising parcels of air to expand and cool
- > heat is not lost to the atmosphere but it is simply spread out over a great area
- higher elevations receive more solar radiation than lower elevations
- > the atmosphere acts as a filter
- > screening out some types of incoming radiation
- > including UV radiation
- > particles in the atmosphere cause scattering of incoming radiation so the amount of solar radiation that reaches the earth’s surface is substantially reduced
What is the mountain mass effect
- large mountains that are massed together do influence regional climates
- > this is referred to as mountain mass effect
How does water bodies regulate climate
- water bodies moderate climate by curbing temperature extremes
- > because water heats and cools more slowly than land
- > as a result, daily and seasonal temperature differences are smaller in coastline mountain ranges relative to ones further on land
What is orographic precipitations
- precipitation that occurs when topographic barriers force air to rise
- mountains act as barriers that intercept air masses
- > forcing them upward
- > leading to cloud formation and increasing precipitation
Compare the windward side of a mountain to the leeward side
Windward side
- > the side of a mountain that receives the prevailing winds
- > receives a lot of orographic precipitation
Leeward side
- > most of the moisture is lost on this side of the mountain
- > the leeward side receives much less rain, producing a rain shadow
What are Chinook winds
- it occurs as air descends on the leeward side of the mountain
- > the air encounters higher atmospheric pressure and compresses
- > causing it to warm
Describe the effect of mountain slopes that are oriented towards the sun
- they receive more incoming solar radiation
- > leads to warmer climates, topographic variation and slope of the terrain can produce local differences in solar radiation equivalent to tens of degrees of latitude
Do north or south facing slopes receive more direct solar radiation in the northern hemisphere
- south facing slopes in the northern hemisphere receives more direct solar radiation
- > opposite in the Southern hemisphere
How does slope angle influence the amount of solar radiation received in the mountains
- maximum solar radiation is received when mountain slopes are perpendicular to the sun;s rays
- > at the equator near 0 degrees latitude, the sun’s rays heat the earth’s surface more directly
- > here mountain slopes receive less solar radiation than flat surfaces
-at increasingly higher latitudes, steeper slopes are more likely to directly intercept the sun’s rays
Will the amount of solar radiation received on a slope facing the sun increasing with increasing slope angle
- yes
- > up to the point where the slope angle is equal to the latitude of the locations
- > eg; for 45 degrees south, maximum solar radiation is received on mountain slopes at a 45 degree angle relative to the horizontal surface
- > for slope aspects facing away from the sun receive minimal solar radiation when their slope angle equals the latitude of their location
What is the temperature inversion regarding mountains
- cold air is denser than warm air
- > so it sinks
- > that sinking cold air will pool in mountainous valleys
What are microclimates
- they are small areas with conditions that differ than that of the surrounding region
- > at high elevations the thin atmosphere exaggerates temperature differences between shaded and sunny areas
- > even on slopes facing the sun, surfaces are sheltered by boulders and other topography
What is the alpine treeline
- absence of trees
- > beyond a certain elevation, environmental constraints prevent tree growth
- > dominant vegetation shifts to low statured plants such as shrubs and herbs and grasses
Why does the alpine treeline exits
- it is not the extreme cold in the winter that restricts tree growth at high evaluations
- > but rather low temperatures during their growing season
- > trees require a minimum growing season of three months
Is the formation of the alpine treeline a global phenomenon
-yes
Do the height of trees become disadvantage at higher elevations
- at lower elevations, higher trees can more effectively capture light resources
- > they are exposed to high winds and have little protection from cold
- > trees become crooked and stunted and are only able to survive by growing horizontally
What is the type of vegetation that grows on higher elevations
-krummholz
Are treelines on mountains higher at latitudes
-yes
- in northern hemisphere, the southern slopes of mountains and mountain ranges receive more solar radiation than the northern slopes
- > therefore, the treelines are usually higher
Do mountains closer to continental interior have higher treeline?Why?
- Yes
- > because less cloud cover so higher levels of solar radiation reaches their surfaces
- also the mountain mass effect means that continental mountains are part of a larger mass of mountains
- > which means they are better able to retain heat than those at the periphery of the range
What is the alpine treeline ecotone
- transitional zones between biomes are called ecotones
- transition zone between forests and alpine tundra is referred to as the alpine treeline ecotone
Describe the differences in climate due to global scale and the local scale
Local scale
->result of slope, aspect and topography
Global scale
->result of latitude, elevation and continentality
