MODULE 2

• Climate


  The inclination of the sun
• The earth gets its heat from the sun
• The earth's movement around the sun (Revolution) and its rotation around its own axis determines the different climatic conditions of the world

  
• Climate is influenced by the complex structure and composition of the atmosphere and by the ways in which it and the ocean transport heat
• For any given area on earth, not only the latitude (the sun's inclination) must be considered but also the elevation, terrain, distance from the ocean, relation to mountain systems and lakes, and other such influences should be considered

  
• Solar radiation


  The sun's heat comes to earth in conduction, convection and radiation
• Direct radiation


  Gain through the openings of the building envelope
• Re-radiation


  Gain through the building envelope
• Air temperature


  Air acquires heat by the direct radiation from sun and by its contact with the earth
• Generally, air temperature is at its lowest just before dawn (5.00-6.00 a.m.) and the highest temperature occurs just afternoon (at 2.00 p.m.)
• Absolute humidity


  The mass of water vapor suspended in a unit volume of the air at a given temperature
• Relative humidity


  The ratio of the amount of water vapor per unit volume of the air to the amount of water vapor per unit volume of saturated air at the same temperature
• Wind


  The natural form of air movement
• The average wind speed is likely to be higher during the day and it frequently drops at sunset especially if skies are clear
• Ventilation


  The process of supplying unconditioned or conditioned air to and removes it from a given space by any method
• Precipitation


  Large scale cloud formation and precipitations result from adiabatic cooling of large air masses, and are effected greatly by the vertical stability of the air
• Weather is momentary composition of individual elements such as wind rain, and sunshine experienced at a particular instant or over a very short period
• Due to the regularity and predictability of climatic variations over the earth's surface, the climate of a given region can be classified according to its chief seasonal characteristics

  
• Climate affects the human comfort
• In the present times, due to rapid urbanization there is a large number of buildings. It has been found that the buildings have a large impact on the micro climatic conditions
• Global climatic zones


  • Hot Humid (Tropical)
  • Hot Arid
  • Temperate (Warm Temperate, Cool Temperate)
  • Cold Climate

  
• Tropical climate


  • Average mean temperature (dbt) 20-30 deg C
  • Small diurnal temperature change/range
  • Humidity level 50% to 100% relative humidity
  • Slow wind flow
  • Overcast sky most of the time
  • High precipitation during the year - average of 1000mm/yr
  • Climate conditions breed insects (flies, mosquitoes, termites)
  • Damp ground condition
• Hot arid climate


  • Temperature can go up to 50 deg C and more in summers
  • High difference between day and night temperature (15 to 20 deg C)
  • Very low precipitation (50 to 150 mm per year)
  • Sky is normally clear and blue, sometimes dusty
  • Strong direct solar radiation during day, escapes into open clear skies during nights
  • High speed dusty winds (20 to 30 km/hr)
  • Loose, sandy soil with poor vegetation
  • Animals adapted to the climate (e.g. camels, foxes, snakes, scorpions)
• Warm temperate (Mediterranean) climate


  • Wet winters, dry summers
  • Extremely dry summers due to sinking air of subtropical highs
  • Plants adapted to extreme difference in rainfall and temperature between winter and summer
  • Frequent fires
• Cool temperate climate


  • Annual temperatures range widely, with warm to hot summers and cold winters
  • Coldest months temperature ranges from -3 to -18 deg C
• Cold climate


  • Long, very cold winters and short, cool summers
  • Very cold air masses from the arctic often move in
  • Large temperature range
  • Precipitation increases during summer months, although annual precipitation is still small
  • Temperature lows around -25 deg C, highs around 16 deg C
  • Average annual precipitation around 31 cm
  • Latitude Range: 50° - 70° N and S
• Wind over a region are determined by several global and local factors such as:

  i. The seasonal global distribution of air pressure

  II. The rotation of the earth

  lii. The daily variations in heating and cooling of land and sea

  iv. Topography of the given region and its surrounding
• Air masses which are made to rise for different reasons produce three main types of precipitation, convectional orographic and convergent.
• The dry-bulb temperature (DBT) is the temperature of air measured by a thermometer freely exposed to the air, but shielded from radiation and moisture. DBT is the temperature that is usually thought of as air temperature, and it is the true thermodynamic temperature.
• Prevailing wind in the Philippines

  • Amihan (NE) – November to April

  • Habagat (SW) – May to October