Lec 1 climate & its components


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Lec 1 climate & its components

  2. 2. NATURAL ENVIRONMENT Space Sun earth RESOURCE ENVIRONMENT Atmosphere Land Vegetation water BUILT ENVIRONMENT Buildings Industry Transport Service
  3. 3. Introduction • The earth's climate is generally defined as the average weather over a long period of time. A place or region's climate is determined by both natural and anthropogenic (human-made) factors. • The natural elements include the atmosphere, geosphere, hydrosphere, and biosphere, while the human factors can include land and resource uses. • Changes in any of these factors can cause local, regional, or even global changes in the climate.
  4. 4. How does climate differ from weather? • Weather is the current atmospheric conditions, including temperature, rainfall, wind, and humidity at a given place. Weather is what's happening right now or is likely to happen tomorrow or in the very near future. • Climate, on the other hand, is the general weather conditions over a long period of time.
  5. 5. The climate of a region can be linked to certain factors which are listed below; Geographical Latitude Season of the year Altitude and Topography Effects of water Atmospheric circulation
  6. 6. Latitude • The geographical latitude of a place on Earth is a measure of its position above or below the equator. – Intensity of solar radiation decreases as latitude increases.
  7. 7. SEASON OF YEAR The orbit of the earth around the Sun is slightly elliptical in shape and the axis of the earth is tilted by 23.5° with respect to plane that passes through the Sun and the Equator. The tilt causes the change in radiation, length of day, and climate between summer and winter.
  8. 8. ALTITUDE AND TOPOGRAPHY • The height of a place above sea level affects its climate because the temperature of the air decreases with altitude. • Air temperature drops by 6.5°C for each 1000 meters increase in altitude.
  9. 9. EFFECTS OF WATER Large masses of water over surface of the earth have a considerable effect on climate, both locally and globally. Oceans and large lakes affect climates by reducing the extremities of air temperature at places nearby.
  10. 10. ATMOSPHERIC CIRCULATION • The movement of large masses of air in the atmosphere influence climate by producing winds that distribute heat and moisture. Atmospheric circulation driven by uneven heating of the Earth by the Sun
  11. 11. World Climate Regions The same climate definitions are used world-wide. Differentiated climate impacts the types of buildings that are appropriate (or not!).
  12. 12. CLIMATIC REGIONS • Hot and Arid Zone The regions, where mean daily maximum dry bulb temperature is 38oC or higher and relative humidity of 40% or less prevail during the hottest month of the year and where the altitude is not more than 500m above Mean Sea Level (M.S.L), may be classified as hot and arid zones. Hot and Humid Zone The regions, where mean daily maximum dry bulb temperature is above 32oC and relative humidity above 40% prevail during the hottest month of the year and where the altitude is not more than 500m above Mean Sea Level (M.S.L), may be classified as hot and humid zones.
  13. 13. • Warm and Humid Zone The regions, where mean daily maximum dry bulb temperature is 26oC to 32oC and relative humidity of 70% or above prevail during the hottest month of the year and where altitude is not more than 100m above Mean Sea Level (M.S.L) may be classified as warm and humid zones. Cold Zone The regions where mean daily minimum dry bulb temperature is 6oC or less prevail during the coldest month of the year and where the altitude is more than 1200m above Mean Sea Level (M.S.L), may be classified as cold zones.
  14. 14. GLOBAL WARMING There is considerable scientific evidence to suggest that the activities of humans are causing the current increase in global temperature. The effects of global warming will change the ecology of many parts of the earth and bring difficulties for people living there. Possible effects of global warming include the following; melting of polar ice causing rise in sea levels and disappearance of land. increase in severity of storms and flooding. change in rainfall patterns, forming new deserts changes in ocean currents, causing changes in local climates changes in patterns of snowfall and ice sheets .
  15. 15. GREEN HOUSE EFFECT The greenhouse effect is a warming of the earth’s lower atmosphere which trap solar energy. The principle greenhouse gasses are; Carbon dioxide Methane CH Nitrogen Oxide Chlorofluorocarbons
  16. 16. COMPONENTS OF CLIMATE • Temperature of air • Humidity of the air • Sky conditions and the amount of direct solar radiation. • Amount of rainfall and • Air movement and prevailing wind direction.
  17. 17. Air Temperature • The temperature of the air or Dry Bulb Temperature (D.B.T.) is the temperature measured in the shade and is recorded at one or two meters above the ground surface by a mercury thermometer in degree Celsius. • It is important to know the mean maximum and mean minimum daily air temperatures for each month of the year. These are the mean of the highest and lowest air temperatures of each day of every month, averaged again by the number of the years for which recordings are available.
  18. 18. Relative Humidity • The humidity of the air is the amount of water contained as vapor in the air. • It can be expressed as absolute humidity, which is the moisture content of the air in terms of grams of water per kilogram of dry air. • However, a much more useful expression is relative humidity, which is the water content of the air as a percentage of the maximum amount of water that the air could hold at that temperature at which the reading is made.
  19. 19. Air Movement • Air movement and prevailing wind directions are usually recorded in terms of the average of daily or monthly changes in wind direction in degrees and speed in meters per second. • Usually data of air movement are recorded ten meters above an open ground (often the local airport); but different topographical conditions, vegetation and buildings can reverse the prevailing wind direction and change its velocity as it affects a particular site.
  20. 20. Sky Conditions • Sky conditions are usually described in terms of the proportion of the sky covered by cloud, averaged over the days of each month and again over the number of years for which records have been maintained. • This may be recorded twice a day (morning and afternoon) as percentages, tenths or eighths of the hemisphere of the sky.
  21. 21. Precipitation The amount of rainfall or precipitation is usually recorded as the average mm/day or mm/month and this gives a useful indication of seasonal changes. Often, average maximum rainfall in 24 hours or the average number of days in which a certain amount (say 2.5 cm.) of rain has fallen is also provided. This information is useful as an indicator of the intensity of rain, which will influence the design of openings, roofs, gutters, etc.
  22. 22. Any Questions?