Climate Varies around the Globe: How and Why

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Climate Varies around the Globe
How and Why?

Yongqin David Chen (???) Department of
Geography and Resource Management The Chinese
University of Hong Kong Shatin, NT, Hong Kong
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Presentation Outline

• Climate controls latitude dominates, others also
  work
• Classification of irregularly distributed
  climates
• Similar latitudes, but very different climates
  Somalia vs Malaysia, Shandong vs Xinjiang

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Climate controls

• (1) Latitude fluctuations in the amount of
  solar radiation received at earths surface,
  represents the single greatest cause of
  temperature differences.
• Land and water marine and continental climates
• Ocean currents poleward-moving warm currents
  (Gulf Stream and Kuroshio Current in N Hemisphere
  and Brazilian and East Australian Currents in S
  Hemisphere, more pronounced impacts in winter)
  and equatorward-moving cold currents (Canaries
  and California Currents in N Hemisphere and
  Peruvian and Benguela Currents in S Hemisphere,
  chilling effects stabilize air masses)
• Pressure centers and prevailing winds - air mass
  movement and gain or loss of heat and moisture,
  seasonal shifting. More maritime on the west
  coast of N America and more continental on the
  east coast
• Mountain barriers and highlands windward and
  leeward sides and rain shadow, Andes and
  Himalayan in S America and Asia, no mountain
  barrier in western Europe leading to moderate
  temperatures and sufficient precipitation in the
  entire region

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• Latitudinal heat balance.
• Average over the entire year, we see that
  equatorward from 36o , the amount of incoming
  solar radiation exceeds the loss from outgoing
  terrestrial radiation. The reverse is true for
  the middle and high (polar) latitudes, where
  losses from outgoing terrestrial radiation exceed
  gains from incoming solar radiation.

• Climate is a 3-D phenomenon
• latitudinal, longitudinal, and altitudinal

• An index of continentality
• gauges the influence of oceans on air temperature
  over continents. In this scheme, North America is
  divided into zones of increasing maritime
  influence continental, subcontinental, maritime,
  and ultramaritime. The greater the maritime
  influence, the less is the contrast between
  average summer and average winter temperatures.
• Adapted from D.R. Currey, Continentality of
  Extratropical Climates. Annals of Association of
  American Geographers 64, No.2 91974)274

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• Major Ocean Currents
• 1. Gulf Stream
• 2. North Atlantic Drift
• 3. Labrador Current
• 4. West Greenland Drift
• 5. East Greenland Drift
• 6. Canary Current
• 7. North Equatorial Current
• 8. North Equatorial Countercurrent
• 9. South Equatorial Current
• 10. South Equatorial
• Countercurrent
• 11. Equatorial Countercurrent
• 12. Kuroshio Current
• 13. North Pacific Drift
• 14. Alaska Current
• 15. Oyashio Current
• 16. California Current
• 17. Peru or Humbolt Current

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• Coastal upwellings
• are important because they provide abundant
  nutrients and therefore encourage rich fishing
  grounds.

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Köppen system - Five principal climate groups
A) Humid tropical - Winterless climates all
months have a mean temperature
above 18oC. B) Dry - Climates where potential
evaporation exceeds precipitation there is a
constant water deficiency. C) Humid
middle-latitude, mild winters - the average
temperature of the coldest month is below 18oC
but above -3oC. D) Humid middle-latitude,
severe winter - the average temperature of the
coldest month is below -3oC and the warmest
monthly mean exceeds 10oC. E) Polar -
Summerless climates the average temperature of
the warmest month is below 10oC.
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• The zone is a strange climatological phenomenon
  a desert (the Somali-Chalbi) on the eastern
  cost in tropical latitudes. The extreme aridity
  is caused, in the main, by the fact that the
  prevailing winds, during most months of the year,
  have a northeasterly or southwesterly direction,
  thus making moist air masses over the land an
  exception rather than the rule (Fig.1).
• The Horn of Africa, by J.F. Griffiths
• Climates of Africa, Vol. 10,
• World Survey of Climatology, p. 134

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• Unusual aridity of the Horn of Africa caused
  Flohn (1964) to ask
• why are the summer rains missing?
• directional divergence produced by overheating at
  the Ethiopian highlands,
• speed divergence produced by the northerly
  increase of the pressure gradient,
• frictional divergence in coast-parallel winds,
• deflection of wind-driven ocean surface current
  and cold upwelling along the coast.

Flohn, H., 1964. On the causes of the aridity of
northeastern Africa. Würzburger Geograph. Arb.,
12 17 pp. (English translation by East African
Meteorological Dept., Nairobi, 1966.)
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• why are the summer rains missing? (1)
  directional divergence produced by overheating at
  the Ethiopian highlands (2) speed divergence
  produced by the northerly increase of the
  pressure gradient (3) frictional divergence in
  coast-parallel winds (4) deflection of
  wind-driven ocean surface current and cold
  upwelling along the coast.

• Amazing fluctuations of annual rainfall amounts
  at Djibouti for 64 years
• - Less than 30 mm for five years
• - 250 mm or more for four years

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• Seasons defined by rainfall patterns
• Jilal December to March, the northeast monsoon
  is in dominance and conditions are dry and
  relatively hot.
• Gu April and May, the transition period,
  relatively wet and hot.
• Hagar June to September, the southwest monsoon
  dominates, bringing relatively cool conditions
  with showers along the coast but dry inland.
• Der October and November, the transition
  period, similar to the Gu but there is the
  important rainy season in the north.

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• Climate of Malaysia
• Tropical annual southwest (April to October) and
  northeast (October to February) monsoons

• What is the Malaysia's climate like?
• Malaysia  has  two  main  seasons,  the 
  Northeast  Monsoon  (November to March) and  the 
  Southwest Monsoon  (May to  September),
  separated  by  two  relatively  shorter 
  intermonsoon  periods. The mean monthly 
  rainfall  amount  shows drier weather conditions
  from May to July and wetter weather conditions
  from  November to January. February is also a 
  relatively dry month. The date of the beginning
  and end of the monsoon varies from year to
  year.They are determined by the beginning of rain
  spell and predominant wind direction.

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The End