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ELEMENTS OF CLIMATE
AND
WEATHER
By
Prof A. Balasubramanian
Centre for Advanced Studies in Earth Science,
University of Mysore,
Mysore
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Introduction:
The climate of a region is ultimately determined by
the radiation energy of the sun, and its distribution
and temporal fluctuations. The long-term state of the
atmosphere is a function of a variety of interacting
elements. They are: Solar radiation, Air masses,
Pressure systems (and cyclone belts),Ocean Currents,
Topography.
1. Solar radiation : Solar radiation is the radiation,
or energy we get from the sun. It is also known as
short-wave radiation. Solar radiation is probably the
most important element of climate.
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Solar radiation first and foremost heats the Earth's
surface which in turn determines the temperature of
the air above. The receipt of solar radiation drives
evaporation, so long as there is water available.
Heating of the air determines its stability, which
affects cloud development and precipitation.
Unequal heating of the Earth's surface creates
pressure gradients that result in wind.
Every location on Earth receives sunlight at least part
of the year.
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The amount of solar radiation that reaches any one
spot on the Earth's surface varies according to:
Geographic location, Time of day, Season, Local
landscape, Local weather.
Solar radiation comes in many forms, such as visible
light, radio waves, heat (infrared), x-rays, and
ultraviolet rays.
Measurements for solar radiation are higher on clear,
sunny day and usually low on cloudy days. When the
sun is down, or there are heavy clouds blocking the
sun, solar radiation is measured at zero.
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2. Temperature : Temperature is a very important
factor in determining the weather, because it
influences or controls other elements of the weather,
such as precipitation, humidity, clouds and
atmospheric pressure.
3. Air masses-wind and storms : An air mass is a
large body of air with generally uniform temperature
and humidity. Air masses control the characteristics
of temperature, humidity, and stability.
Location relative to source regions of air masses in
part determines the variation of the day-to-day
weather and long-term climate of a place.
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Winds :-
• The horizontal movement of the atmosphere is
called wind.
• Wind can be felt only when it is in motion.
• Wind is the result of the horizontal differences in the
air pressure.
• Wind is simply the movement of air from high
pressure to low pressure.
• The speed of the wind is determined by the
difference between the high and low pressure.
• The greater the difference the faster the wind speed.
• Closer the isobars stronger the winds.
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• The wind brings with it the temperature of the area it
is coming from, therefore a high pressure in a warm
region will make the temperature in the low pressure
area higher.
• Wind-chill is the effect of the wind making it feel
colder than it actually is.
• As the wind speed increases air is moving more
quickly and therefore removes warm air therefore
making it seem colder than the actual temperature.
4. Pressure systems:
•Air pressure is the weight of air resting on the earth's
surface.
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•Air has specific weight.
•This weight exerted by the air is atmospheric
pressure.
•It is defined as the force per unit area exerted against
a surface by the weight of air above that surface in the
Earth's atmosphere.
Pressure systems have a direct impact on the
precipitation.
In general, places dominated by low pressure tend to
be moist, while those dominated by high pressure are
dry.
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The seasonality of precipitation is affected by the
seasonal movement of global and regional pressure
systems.
5. Ocean Currents:
Ocean currents greatly affect the temperature and
precipitation of a climate.
Those climates bordering cold currents tend to be
drier as the cold ocean water helps stabilize the air
and inhibit cloud formation and precipitation. Air
traveling over cold ocean currents lose energy to the
water and thus moderate the temperature of nearby
coastal locations.
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Air masses traveling over warm ocean currents
promote instability and precipitation. Additionally,
the warm ocean water keeps air temperatures
somewhat warmer than locations just inland from the
coast during the winter.
6. Topography:
Topography affects climate in a variety of ways.
The orientation of mountains to the prevailing wind
affects precipitation.
Windward slopes, those facing into the wind,
experience more precipitation due to orographic uplift
of the air.
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Leeward sides of mountains are in the rain shadow
and thus receive less precipitation.
Air temperatures are affected by slope and orientation
as slopes facing into the Sun will be warmer than
those facing away.
Temperature also decreases as one moves toward
higher elevations.
7. Humidity :
• Atmospheric moisture is the most important element
of the atmosphere which modifies the air temperature.
• Humidity is the measurable amount of moisture in
the air of the lower atmosphere.
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• There are three types of humidity:-
a) Absolute humidity:-
The total amount of water vapor present in per
volume of air at a definite temperature.
b) Relative humidity:- Is the ratio of the water vapors
present in air having a definite volume at a specific
temperature compared to the maximum water vapors
that the air is able to hold without condensing at that
given temperature.
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c) Specific humidity:-
Is defined as the mass of water vapor in grams
contained in a kilogram of air and it represents the
actual quantity of moisture present in a definite air.
•The humidity element of weather makes the day feel
hotter and can be used to predict coming storms.
•The humidity element of climate is the prolonged
moisture level of an area that can affect entire
ecosystems.
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8. Precipitation :
• Precipitation is the term given to moisture that falls
from the air to the ground.
• Precipitation includes snow, hail, sleet, drizzle, fog,
mist and rain.
• Precipitation is simply any water form that falls to
the Earth from overhead cloud formations.
• As an element of weather, precipitation determines
whether outdoor activities are suitable or if the water
levels of lakes and rivers will rise.
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• As an element of climate, precipitation is a long-
term, predictable factor of a region's makeup.
• For instance, a desert may experience a storm
(weather) though it remains a typically dry area
(climate).
9. Cloudiness :
Clouds are suspended water in the atmosphere.
• Clouds are usually the most obvious feature of the
sky.
• Clouds give us a clue about what is going on in our
atmosphere and how the weather might change in the
hours or even days to come.
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• Each type of cloud forms in a different way, and
each brings its own kind of weather.
• Clouds play multiple critical roles in the climate
system.
• In particular, being bright objects in the visible part
of the solar spectrum, they efficiently reflect light to
space and thus contribute to the cooling of the planet.
• A small increase in cloud cover could, in principle,
balance the heating resulting from greenhouse gases.
• Clouds are the base for precipitation.
• In summer cloudy days provide protection from the
rays of the sun.
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• In winter cloudy skies at night diminish nocturnal
radiation and check the fall of temperature.
• Clear calm winter nights are usually the coldest and
helps in condensation.
10. Visibility :
• The most critical weather element.
• Obstructions to visibility include clouds, fog, smoke,
haze, and precipitation.
• is represented by the meteorological optical range
(MOR).
• b) varies with the background illumination.
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•In extremely clean air in Arctic or mountainous
areas, the visibility can be up to 70 kilometres (43 mi)
to 100 kilometres (62 mi).
• visibility is often reduced somewhat by air pollution
and high humidity.
Fog and smoke can reduce visibility to near zero,
making driving extremely dangerous.
•The same can happen in a sandstorm in and near
desert areas, or with forest fires.
Heavy rain (such as from a thunderstorm) not only
causes low visibility, but the inability to brake quickly
due to hydroplaning.
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• Blizzards and ground blizzards (blowing snow) are
also defined in part by low visibility.
Controls of climate:
1. Latitudes;
2. Altitude;
3. Land and water;
4. Distance from land and water;
5. Low and high pressure cells
6. Winds and air masses;
7. Mountains barriers/Relief;
8. Ocean currents.
