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Some Review: Small Scale Winds

Some Review: Small Scale Winds. Daytime. Night. Source: Ahrens, 2001. Mountain Valley Breezes. Daytime The sun heats the hillslope, causing air to move up the slope Night Night radiation cools the slopes Cooler, denser air moves downslope. Source: http://apollo.lsc.vsc.edu.

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Some Review: Small Scale Winds

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  1. Some Review: Small Scale Winds Daytime

  2. Night Source: Ahrens, 2001

  3. Mountain Valley Breezes Daytime The sun heats the hillslope, causing air to move up the slope Night Night radiation cools the slopes Cooler, denser air moves downslope Source: http://apollo.lsc.vsc.edu

  4. Chinook Winds Cooling At MALR 6°C/km Warming At DALR 10 °C/km Warming At DALR 10 °C/km Cooling At MALR 6°C/km Cooling At DALR 10 °C/km X X VANCOUVER LETHBRIDGE 12°C 8°C More sensible heat

  5. Review: Geostrophic Winds Effect of Air temperature on 500 mb heights

  6. Geostrophic winds Wind flows along isobars PGF counterracted by inertial CoriolisForce (see any 500 mbar height map)

  7. Global Climate Systems and Biomes

  8. Weather vs. Climate • Weather • Condition of the atmosphere at any place and time • http://weatheroffice.ec.gc.ca/forecast/city_e.html?yql • Climate • Characteristic behaviour of weather over time • Includes averages and extremes • http://www.theweathernetwork.ca/weather/stats/pages/C02080.htm?CAAB0194 • Climatology is the study of climate • Climatic regions: zones with characteristic weather patterns • Empirical (statistics) or genetic (causative) classification • Eg. Köppen-Geiger Climate Classification System (1928)

  9. Climographs LETHBRIDGE, AB VANCOUVER, BC

  10. Determinants of climate: • Distribution and seasonal variation of solar insolation intensity (zenith angles and daylength) • Atmospheric and oceanic global circulation patterns • Controls of temperature: altitude and latitude, land-water heating differences, cloud cover, polar front • Controls on precipitation: distribution of pressure systems, lift mechanisms (convergence, convection, orographic, frontal), location of ITCZ, subtropical high pressure, jet streams

  11. Effect of Altitude Source: Solomon, 2000

  12. Effect of Latitude and Cloud Cover Solar insolation is reduced with latitude or cloud cover

  13. Global Circulation Patterns

  14. Climate Distribution Classification systems: Köppen-Geiger, Thornthwaite (not shown) A Tropical - equatorial regions C Mesothermal – eg. Mediterranean, marine W. coast D Microthermal – eg. humid continental, subarctic E Polar H Highland – cooler than surroundings B Dry – deserts and steppes See Figure 6-4

  15. A Tropical Climates Straddle equator: 20N to 20S Coldest month is above 18C Consistent daylength, small zenith angles Includes tropical rainforest, tropical monsoon and tropical savanna

  16. 1. Tropical Rain Forest Climate • Warm and moist • Thunderstorms – local convection in convergent ITCZ • All months receive more than 60mm • Precipitation pattern follows migration of ITCZ • Two wetter seasons near equator, one wetter season near tropics • High rainfall and solar insolation sustain lush, evergreen, broadleaf tree growth • High leaf area index (LAI) • Dark canopy floor with sparse vegetation • Rapid decomposition – more nutrient mass in vegetation than soil

  17. Rainforest Climograph Manokwari, New Guinea Little variability in average monthly temperature Driest month receives more than 100 mm of rainfall Source: http://www.geocities.com/Athens/Parthenon/1020/biome.html

  18. Tropical Rain Forest Vegetation Layers in the Tropical Rain Forest Canopy Source: http://www.world-builders.org/lessons/less/biomes/rainforest/tropi_rain/tropgifs

  19. Layers in the Tropical Rain Forest Canopy • Emergents • Trees “emerge” from the forest canopy • Exposed to high light, fluctuating temperatures, higher winds • Huge trees (up to 70m) with massive, buttressed trunks • Seed dispersal often by wind • Home to many birds and animals looking for safety from predators (eg. eagles, bats, monkeys, snakes, butterflies) • Buttressed trunks to support weight of tree, water and • epiphyte biomass

  20. Canopy Layer • Continuous layer (about 45 m) • Most have buttressed trunks • Especially high diversity of plants and animals • Same tree found once or twice per square kilometre • Lianas (vines) connect trees • Epiphytic vegetation common -28,000 species (eg. mosses, bromeliads, ferns, orchids) • Abundant fauna (eg. monkeys, sloths, bats, treefrogs, ants, beetles, parrots, hummingbirds and snakes)

  21. Understorey Layer • Receives 2-5% of incident light (blocked by canopy) • Understorey plants photosynthesize most efficiently under low light (low respiration rates) • Layer consists of small trees (eg. dwarf palms) and seedlings of taller trees • Low wind: insect pollination, strong smelling and conspicuous flowers often on trunks • Abundant fauna (eg. insects, snakes, frogs, parakeets, leopards, jaguars etc.)

  22. Forest Floor • Approximately 1% of light incident upon the canopy • 100% relative humidity, less temperature variation • Rapidly-decomposing organic matter • Few flowering plants • Fungi thrive on decomposing organic matter • Large mammals forage for roots and tubers (eg. tapirs) • Many insects (eg. termites, cockroaches, beetles, centipedes, millipedes, scorpions and earthworms)

  23. Deforestation • >50% already gone (pasture, timber, fuelwood, farming) • Approximately 169,000 km2 lost each year • Fire clears land for agriculture (food production, rubber, coffee etc.) • Slash and burn – soil nutrient reserves quickly exhausted • Destruction generally along transportation networks •  Tropical Forestry Action Plan (FAO, UNDP, WB, WRI) • Remote sensing and GIS play key role in monitoring

  24. 2. Tropical Monsoon and Savanna Climates • Tropical Monsoon Climates • Rainfall from ITCZ affects regions for 6-12 months of the year (eg. text example Yangon, Myanmar) • Seasonal variation in winds and precipitation • 1 or more months have less than 60mm of precipitation • Evergreen broadleaf trees grade toward thorn forests along drier margins with savanna

  25. Tropical Monsoon Climograph Dry season during the Northern Hemisphere winter Wet season during the summer

  26. Tropical Savanna Climates • ITCZ effect for <6 months of the year • Winters are dry (subtropical high pressure) • Summers are wet (influence of ITCZ) • Tropical cyclones possible near east coasts • Grasslands dominate: scattered, drought-resistant trees • Text example: Mérida, Mexico (relatively wet) and Kenya

  27. Tropical Savanna Distribution

  28. Savanna Climograph Long dry season during the Southern Hemisphere winter Wet season during the summer http://www.cotf.edu/ete/modules/msese/earthsysflr/savannah.html

  29. Vegetation in the Tropical Monsoon and Savanna Climate Zones: • Tropical Seasonal Forest and Scrub • Poleward transition from tropical rain forest to grasslands • Monsoonal forestsopen woodlandsscrub woodlandthorn forestsdrought-resistant scrubgrassland • Leaf loss and dry season flowering during seasonal moisture deficits

  30. Monsoonal forests: • Discontinuous, 15 m high canopy • Denser undergrowth • Orchardlike parkland with grassy openings in drier sectors • Flat-topped acacia trees become common in drier zones • Examples: Caatinga (Brazil), Chaco (Paraguay), Brigalow (Australia), Dornveld (S. Africa) • Wildlife: elephants, large cats, rodents, ground-dwelling birds • Koalas and cockatoos in Australia

  31. Monsoon Forest of India Increased light penetration compared to lowland rain forest Discontinuous canopy and lower LAI

  32. Vegetation of the tropical savanna • Large expanses of grassland, interrupted in areas by trees and shrubs • Trees and shrubs are xerophytic (small, waxy, thick leaves) • Most expansive in Africa (Serengeti plains, Sahel) • also Los Llanos (Venezuela), Campo Cerrado, Pantanal (Brazil) • Fires common during the dry seasons (beneficial if early) • Affected by desertification • Soils richer in humus than tropical rain forests: sorghum, wheat, peanuts can be grown • Home to large land mammals in Africa: lion, cheetah, zebra, giraffe, buffalo, gazelle, wildebeest, antelope, rhinoceros and elephant

  33. El Nino Southern Oscillation Interannual climatic variability at the global scale Caused by changing atmospheric and oceanic circulation in the tropical Pacific Ocean

  34. See http://www.cdc.noaa.gov/map/clim/sst_olr/sst_anim.shtml

  35. C Mesothermal Climates • 1.  Humid Subtropical Hot Summer Climate • Influenced by maritime tropical air masses in summer • Continental polar and maritime tropical air masses mix in fall/winter/spring: frontal precipitation • Convectional precipitation in moist, unstable summer airmass • Tropical cyclones near coasts in summer and fall • 1000 – 2000 mm/yr total

  36. Examples: southeast U.S., southeast China, southern Japan, • northern Argentina • Broadleaf and mixed forest

  37. Humid Subtropical Winter Dry Climate • Similar to above, but dry in winter • Heavy precipitation in summer • Circulation in winter prevents moist, tropical air mass interaction with pressure systems • eg. much of southern China, eastern South Africa • Broadleaf and mixed forest, but largely deforested • (see Figure 6-11)

  38. 3. Marine West Coast Climates • Mild winter and relatively cool summer • Winter maximum of precipitation, especially in southern zones • Heavy precipitation in mountains (may exceed 4000 mm/yr) • Precipitation varies at low altitude: much more precipitation in northern portions of the Marine West Coast Climate than in the south • Dominated by maritime polar air masses but unusually mild for their latitudes • Coastal fog is common

  39. Temperate Rain Forest • Narrow margin of Pacific NW North America • Less species diversity than TRF • Needle/broadleaf trees, ferns and undergrowth • Tallest tree in world (Sequoia sempervirens – • Redwood) may exceed 100m • Also Douglas Fir, Spruce, Cedar, Hemlock • Moist, lush vegetation • Fauna: Bear, badger, deer, wild pig, wolf, • bobcat, fox and numerous bird species

  40. 4. Mediterranean Dry Summer Climates • Poleward of subtropical high pressure on west coasts • Subtropical high prevents precipitation and influx of tropical moist air in summer • At least 70% of precipitation occurs in the winter • Summer water resource problems • Agriculture requires irrigation • Hot summer and cool summer varieties • Cool offshore currents enhance stability of marine air mass along west coasts • Examples: Mediterranean, southwest California, northwest coastal Mexico, central Chile, southern tip of South Africa

  41. Mediterranean Shrubland: “Chaparral” • Sclerophyllic shrubs • Short-statured, deep roots, • leathery leaves, low branches • Grass between shrubs • Fire adaptation • Resprouting capability • Cork Oak, Pine and Olive trees • in Mediterranean • Commercial agriculture: fruits, • vegetables and nuts • Fauna: deer, coyote, wolf, bobcat, rodents and birds

  42. D Microthermal Climates • Temperature variation is high due to season and air masses • 1. Humid Continental Hot Summer Climate • Frequent passage of pressure systems • Maritime tropical air masses and convection influence climate in summer • Occasional intrusion of cold, polar air in winter • Some areas have a dry winter, but others have similar year-round precipitation totals. Why ? • Influence of coastal storms or lake effect snows in winter • Corn, soybean, hog and cattle farming without irrigation • Midlatitude broadleaf and mixed forest • See New York City Climograph (Figure 6-15)

  43. 2. Humid Continental Mild Summer Climate • Precipitation is generally lower than in the hot summer climate • Temperature is cooler than in the hot summer climate • Snowmelt in winter important for soil moisture recharge • Winter is relatively dry except near lakes and oceans • Agriculture: includes dairy cattle, poultry, flax, sunflowers, sugar beets, wheat and potatoes (usually without irrigation) • Midlatitude broadleaf and mixed forest tending to needleleaf forest to north on shallower soils • Examples: Great Lakes, much of northeast Europe • (See Moscow climograph – Fig 6-16)

  44. Midlatitude Broadleaf and Mixed Forest • Very productive in summer, senescence in fall • High LAI, limited undergrowth in old growth forest • Trees: Maple, Oak, Beech, Elm, Chestnut in Great Lakes, New England and Maritimes, mixed with White Pine, Red Pine and Eastern Hemlock • Fauna: Red fox, white-tailed deer, southern flying squirrel, opossum, bear and a great variety of birds (eg. cardinal, blue jay)

  45. 3. Subarctic Climates • Very long, cold winters – dominated by high pressure • Discontinous or continuous permafrost at high latitude • Boreal forests or Taiga where growing season sufficient • Fir, Spruce, Larch and Birch • Open northern woodlands and tundra in far north • Winters are generally drier than summer • However, the Dry Winter form of subarctic climates occurs only in Russia • Bitter cold occurs in these areas in winter • Verkoyansk has an average 63C temperature range

  46. Climograph: Subarctic climate Low precipitation and cold temperatures in Winter Huge temperature range

  47. Needleleaf forest and Montane Forest • Boreal forest from Alaska, across northern portions of AB, SK, MB, ON, QC to east coast of Newfoundland and Labrador • Taiga from European plain across much of Russia through Siberia • Only extensive in N. hemisphere, but occur at montane sites in S. Hemisphere • Trees: Pine, Spruce and Fir • Fauna: wolf, moose, bear, lynx, beaver, wolverine, small rodents, hawks, eagles, grouse, owls and migratory birds

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