Climatology, landscape and environmental studies.
• ROHIT KUMAR
• ASSSISTANT PROFESSOR
MBS SPA 2015
Any local deviation from the climate
of a larger area, whatever the scale
Immediate local climatic conditions
such as temperature, humidity, solar
radiation, wind, etc.
Climate of a small area which is
different from the larger area
It can be of a space as small as the
protected inner courtyard of a
building and as large as a city which
have different climatic conditions of
the larger area around.
Scale of microclimate
• To a botanist, Microclimate can be of a single plant leaf, with its
temperature and moisture conditions, its population of insects
and micro organisms, on the scale of a few centimetres.
• To an urban geographer, micro climate may mean the climate
of a whole town.
• SITE CLIMATE: Climate of the area available and is to be used for
the given purpose, both in horizontal extent and in height.
• The task of the designer is to take advantage of the favourable
and mitigate the adverse characteristics of the site and its
Factors affecting the local deviation are:
• Topography: Slope, orientation, exposure, elevation, hills or
valleys at or near the ground.
• Ground surface: (Whether natural or man‐made): affect in
terms of reflectance, permeability and the soil temperature as
these affect the vegetation and this in turn affects the climate.
(woods, shrubs, grass, paving, water, etc.).
• Three dimensional objects: such as trees, tree belts, fences,
walls and buildings as these may influence air movement, cast a
• The air temperature near the ground is dependent on heat
gained/lost by the earth surface.
• heat exchange varies with day/night, season, time of the year,
latitude and cloud cover.
• During the day, with the heating of the earth surface, the air
nearest to the ground(within 2 metres) gains most temperature.
At night, the direction of heat flow is reversed.
• The phenomenon of decreasing temperature with increase in
• Cold air tends to settle in the deepest depressions and behaves
as a liquid. It does not flow quite readily like water but like a
highly viscous liquid.
• A difference of 7‐8 m in height can cause 5‐6 deg drop in temp.
This is why hill stations are preferred locations during
Jaisalmer 830’ 45º C
Mt. Abu 4003’ 30º C
• Relative humidity is inversely proportional to temperature.
• During the day, when the lowest layer of air is heated by the
ground surface, RH decreases rapidly. This leads to higher rate
of evaporation(If there is water body, vegetation, etc.) leading
to increase in Absolute Humidity.
• At night, When dew point temperature is reached, fog
formation takes place and if there is no further rapid cooling
nor air movement, a deep layer (40‐50m) of fog develops.
• When ground level changes by more than 300m, the
windward side receives more rainfall than the regional
• In an extreme case, on a large site located on the top of a hill
and extending down to both the slopes, the leeward side
receives only 25% of the rain received by the windward side.
• REASON: hill forces the air mass to rise which cools it down
and it is no loner able to support the moisture carried. This
effect can also be caused by towns. The opposite is also true.
• Abrupt change in topography may cause a permanent cloud
cover like in the rock of Gibraltar.
Warm air rises
Cool air drops
Recognizing air channels can help reduce
discomfort or enhance comfort
precipitates out as
air moves up slopes
L: p.73 Fig. 5.2d
The leeward side of a hill can protect from unwanted
• Three ways:
• Transparency of the atmosphere: Cloud formation, air
pollution, smog, smoke, dust, etc. affect the intensity of solar
radiation on the horizontal plane.
• Slope and orientation of the site: Intensity on the actual
ground surface. At mid latitudes, a site sloping towards the
pole will receive much less radiation than the site sloping
towards equator. (Effect is negligible around equator)
• Obstructions like hills, trees, existing buildings which may cast
a shadow on the site. The effect is most pronounced wen the
objects like on east or west of the site.
• Air flowing across any surface is subjected to frictional
forces. Wind speed near the round is less than the speed than
higher up and the difference depends on the
smoothness/evenness of the surface.
• On hilly sites, the greatest speeds are experienced at the crest
of the hills. The valleys may experience I wind speed if their
direction coincides wit the direction of the wind flow.
• Large stretches of water can give rise to local coastal breezes.
On‐sore breezes (from water to land) during the day may
lower the maximum temperature by 10 deg Celsius but are
likely to increase humidity.
• On shore lake breezes are rarely effective beyond 400m but
the sea breezes are much more effective.
• Wind speed can be reduced after a long horizontal barrier by
50% at a distance of ten times and by 25% at a distance of 20
times the height.
Warm air rises
Cool air drops
Morning and afternoon
“diurnal winds” are
intensified in canyons and
on sloped surfaces and
diverted by hills and ridges
Large bodies of water
A thermal mass that
can act as at thermal
buffer/ heat sink
Lakes & Oceans
are reduced in
are raised in
Onshore winds occur
when water temperature
is lower than adjoining air
temperature over land.
Offshore winds are the
• Vegetation is usually regarded as a function of climate but in
itself it can influence the local or site climate.
• Forming an intermediate layer between the earth surface and
the atmosphere, they have a moderating effect on air
temperature, humidity, radiation and air movement.
• increase the surface of contact to a higher layer by a factor of
4 to 12 times.
Trees provide shade and
affect the micro climate
of the place.
Trees and shrubbery give
off moisture that
Trees, shrubbery, and
grasses provide shade that
prevents moisture from
Permeable surfaces reduce
evaporative cooling Reeves House, Lopez Island, WA
• Man‐made environments create micro climate of their own
deviating from the regional climate. The factors causing
• Changed surface qualities: (pavements and buildings) :
Increased absorbance of solar radiation, reduced evaporation.
• Buildings: Casting a shadow, acting as barriers to winds,
channelizing winds, storing heat in their mass and releasing it
• Energy seepage: through walls and ventilation of heated
• Atmospheric pollution: Presence of solid particles in urban
atmosphere may assist in formation of fog and induce rainfall.
• Temperature can be 8 deg higher in cities tan the surrounding
country side, humidity can be reduced by 5‐10%, wind velocity
can be reduced by half.