climates

classification of climatic regions

by latitude:
- equatorial
- tropical
- sub-tropical
- temperate
- sub-polar
- polar
by temperature-rainfall:
- a region can be graphed on a kind of climograph called a thermohyet which has mean monthly temperature on Y-axis and mean monthly rainfall on X-axis
Koeppen-Geiger system:
- a climate can be classed using 3 letters:
  - 1st letter: relates to temperature
  - 2nd letter: relates to rainfall
  - 3rd letter: relates to temperature
by frequency of different types of air masses:
- parallels the Koeppen-Geiger system
- is relevant to shape of thermohyet loop
by statistics:
- usually by factorial analysis

factors that may effect climate:
- random element inherent in the atmosphere
  - including volcanic eruptions
- regular rhythms due to Earth's spin & orbit:
  - those which account for daily & seasonal changes, modified by persistence
  - Milankovitch variations due to long term oscillation of earth's axis every 40,000yrs & variation in its orbital eccentricity every 92,000 yrs
- not so regular rhythms such as:
  - sunspot activity
  - rotation of the oceanic gyres
  - the Southern Oscillation
  - the quasi-biennial oscillation
  - continuous processes such as mountain building & erosion
  - polar icebergs floating away from the polesmay cause sudden hemispheric cooling by as much as 5degC within a century
- there may be threshold states which once passed create an alternative oceanic or atmospheric current and thus climatic conditions
  - eg. Ice Age perhaps
  - eg. reversal of currents during an El Nino year
- influence of human activities:
  - carbon dioxide & other greenhouse gas levels:
    - increased production by industry, etc
    - decreased removal by decreased vegetation & forests
  - stratospheric dust via pollution, nuclear explosions
  - altered ocean currents & water flows by damming & the creation of artificial lakes
  - altered surface albedo by replacing vegetation with bitumen, etc
  - destruction of stratospheric ozone levels