Introduction
Agrometeorology is a science
investigating the meteorologic, climatologic and hydrologic conditions which
are significant for agriculture owing to their interaction with the objects and
processes of agricultural production.
A science dealing with climatological conditions which
have direct relation or relevance to agriculture.
Growth, development and productivity of plants depend on
several factors. These factors can be
broadly divided into two major groups viz., internal factors (Genetic or
hereditary) and external or environmental (surrounding) factors. The environmental factors are
i) Climate
(Meteorological elements)
ii) Edaphic
(Soil)
iii) Biotic
(living organisms)
iv) Physiographic
(elevation)
v) Anthrophic
(man)
This course on agrometeorology deals with the behaviour
of the weather elements and their effect on crop production.
Climate: The aggregate of
weather conditions over a longer period of time
Weather: The state of the
atmosphere with respect to wind, temperature, cloudiness, relative humidity,
pressure etc., at given time and at a given time.
Agroclimatic
regions: The grouping of different
physical areas within the country into broadly homogeneous zones based on
climatic and edaphic factors.
- The word
“Meteorology” is of Greek origin, meaning, discourse or study on things about and included
meteors and optical phenomena.
- An
international Meteorological Organisation had been established in
1878.
- The world
meteorological organisation (WMO) took its present form in 1951. It serves as a specialized agency to
carryout the world wide exchange of meteorological informations with the
head quarters in Geneva, Switzerland.
- The India
Meteorological Department (IMD) was established in the year 1875. The division of Agricultural Meteorology
was started by the IMD in 1932 to meet the needs of agriculturist and
researchers.
Composition
of Atmosphere
Constituent
|
Percent
by volume
|
Nitrogen (N2)
|
78.08
|
Oxygen (O2)
|
20.94
|
* Argon (Ar)
|
0.93
|
Carbon dioxide (Co2)
|
0.03
|
* Neon (Ne)
|
0.0018
|
* Helium (He)
|
0.0005
|
Ozone (O3)
|
0.00006
|
Hydrogen (H2)
|
0.00005
|
* Krypton (Kr)
|
Trace
|
* Xenon (Xe)
|
Trace
|
Methane (Me)
|
Trace
|
·
Inert chemically never found in any chemical
compounds.
- The maximum
concentration of Ozone are found between about 30 and 60 km.
- The water
vapour content of air may vary from 0.02 per cent by volume in a cold dry
climate to nearly 4 per cent in the humid tropics.
Troposphere:
- It contains
about 75 per cent of the total gaseous mass of the atmosphere.
- Under normal
conditions, the height of the troposphere at the poles is about 8
kilometers, while at the equator it is about 18 kilometers.
Stratosphere:
- The
stratosphere begins at the troposphere which forms its lower
boundary. The lower stratosphere is
isothermal in character 18 to 50 kilometers.
- Presence of ozone layer is a special feature of this structure.
Mesosphere:
- Mesosphere
exist from the height of 50 to 80 Km from the surface of the earth
- In this
layer the temperature increases with height @ 5oC/km.
Ionosphere:
- Above Mesosphere, the temperature fulls again reaching a minimum of about 100oC
at a height of 80 km.
Exosphere:
- The outer
most layer of earth's atmosphere is known as the exosphere which lies between
400 and 1000 kilometers.
Latitude:
Angular distance, measure in degrees, north or
south from the equator.
Equator: An imaginary
circle around the earth, equally distant at all points from both the North pole
and the south pole.
Longitude: (Length)
Distance east or west on the earth's surface measured as an are of the equator
(in degrees upto 189o or by the difference in time) between the
meridian passing through a particular place and a standard or prime meridian,
usually the one passing through Greenwich, England.
Meridian: A great circle
of the earth passing through the geographical poles an any given point on the
earth's surface.
Weather
elements
1.
Solar radiation.
2.
Temperature, Air pressure
3.
Wind velocity and wind direction
4.
Moisture (humidity)
5.
Cloudines (Sunshine hours)
6.
Precipitation (Rainfall)
The crop region are classified on the basis of
average rainfall which are as follows:
Rainfall
(mm)
|
Name
of the climatic region
|
Less than 500
|
Arid
|
500 – 750
|
Semi Arid
|
750 – 1000
|
Sub humid
|
More than 1000
|
Humid
|
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