CLIMATE Global climatic factors
Weather and climate Weather: short term variation of the state of a region
Weather and climate Weather: short term variation of the state of a region Climate: statistical weather information over a long period of time
Global climatic factors 1. Solar Radiation Quality: Ultra Violet rays V I B G Y O R Infra Red Rays 290 380 mn 380 700 nm 700 2300 nm
2. Solar Radiation Quantity:
3. Tilt of the Earth s Axis:
4. Earth s Thermal Balance: Radiation Evaporation convection
5. Winds:
6. Topography: Air movement Water bodies Pressure and temperature patterns.
Solar Radiation Elements of Climate
Ambient Temperature
Humidity
Precipitation
Wind
Sky conditions
Climatic zones
2 major factors affecting human comfort are- Air temperature & Humidity
Tropical climates Heat is a dominant problem. Annual mean temperature is not less than 20` c.
Warm-Humid climate Places- lagos, mombasa, colombo, singapore, jakarta, quito, pernambuco. Temperature- day- 27-32`c Temperature- night- 21-27`c Annual rainfall- 2000-5000 mm Organic building materials tend to decay rapidly. Mould and algal growth, rusting and rotting due to high humidity.
Warm-humid island climate Places- caribbeans, the phillippines and other island groups in pacific ocean Temperature- day- 29-32`c Temperature- night- 18-24`c Annual rainfall- 1250-1800 mm High salt content in atmosphere encourages corrosion in coastal areas.
Hot-dry desert climate Places- assuan, baghdad, alice springs, phoenix Two seasons- hot & cool Temperature- day (hot)- 43-49`c day (cool)- 27-32`c Temperature- night (hot)- 24-30`c night (cool)- 10-18`c Annual rainfall- quite variable- 50-155 mm Winds are hot, dusty and sandy which often develops into dust-storms. High day-time temperatures and rapid cooling at night may cause materials to crack and break up.
Hot-dry maritime desert climate Most unfavourable climates on the earth Places- kuwait, anto-fagasta, karachi Temperature- day (hot)- max aboutt 38`c day (cool)- 21-26`c Temperature- night (hot)- 24-30`c night (cool)- 10-18`c Precipitation is very low. Dust and sand-storms may occur Salt-laden atmosphere accelerates corrosion.
Composite/monsoon climate Places- lahore, mandalay, asuncion, kano, new-delhi seasons Hot-dry Warm-humid Cool-dry Day time 32-43`c 27-32`c Up to 27`c Night time 21-27`c 24-27`c 4-10`c Annual rainfall- 500-1300 mm Winds during dry period are hot and dusty Winds during monsoon are fairly strong and steady Termites are common and occasional condensation problems.
Tropical upland climate Places- addis ababa, bogota, mexico city, nairobi Temperature- day- 24-30`c Temperature- night- 10-13`c Precipitation- is variable- rarely less than 1000 mm Winds are variable, predominantly north-east and south-easterlies. Heavy dew at night Strong radiation loss at night during the dry season, which may lead to formation of radiation fog. Hail may also occur sometimes.
Macroclimate Every city, town or village may have its own climate, slightly different from the climate described for the region Marcroclimate
Site Climate It is any local deviation from the climate of a larger area. For the urban geographer, the term microclimate may mean the climate of a whole town.
Factors which may cause local deviation Topography: Slope, Orientation, Exposure, Elevation, Hills, Valleys at or the near the site Ground Surface, Weather: Natural or manmade, its reflectance, permeability and soil temperature, as these affect vegetation and in turn climate
Three dimensional objects: Trees, Fences, Walls, Buildings. Influence air movement, cast shadows, divide and distinguish
Air Temperature Dependent upon the amount of heat gained or lost at the earth s surface Heat exchange at surfaces varies between night and day, seasons, latitude.
Humidity TEMPERATURE RELATIVE HUMIDITY ABSOLUTE HUMIDITY AT GROUND HIGH LOW HIGH AT 2M LOWER HIGHER LOWER
Precipitation Where the ground changes level by more than 300m, the windward slope can be expected to receive a rainfall more than regional average, and the leeward slope correspondingly less. The leeward half receives only 25% of the rain received by the windward side.
sky conditions Very rare phenomena. They do not vary They vary in short distances if there is considerable change in topography. For examplethe flag like permanent cloud on the leeward side of the rock of gibraltar.
solar radiation 3 factors affecting intensity of solar radiation 1. Transparency of the atmosphere. pollution, smoke, smog or dust and local cloud formation can reduce radiation. 2. Slope and orientation of the site. equator negligible effect higher latitudes effective and imp. mid latitudes site sloping less towards poles radiation site sloping more equator radiation
3. Hills, trees and existing buildings. cast shadow over the site effective if such obstructions ie on east or west of the site.
air movement Near the ground wind speeds is always less than higher up. Wind speed can be reduced after a long horizontal barrier by 50% at a distance of then times the height and by 25% at a distance of twenty times the height.
special characterisics 1. Thunderstorms. 2. Dust and sandstorms 3. Earth quakes
vegetation Intermediate layer between the earths surface and the atmosphere. Indirectly affect- air temperature. Humidity. Radiation. Air movement. Very helpful in hot and dry regions
urban climate Manmade environments create microclimates of their own which are different from the macroclimate of their region. Factors cousing deviations of the urban climate from regional climate are:- 1. Changed surface qualities. 2. Buildings 3. Energy seepage 4. Atmospheric pollution
site climate data Steps 1. Collect regional climatic data. 2. Focus on the parameters affecting deviation on site.