indian rainfall and atmosphere

1. Indian rainfall and Atmosphere
Course: B.Sc. Agricultural
Subject : Principle of Agronomy and Agricultural Meteorology
Unit: 5

2. 1. Reservoir – Oceans, air (as water
vapor), groundwater, lakes, evaporation,
wind and precipitation (rain) move water
from oceans to land.
2. Assimilation – Plants absorb water
from the ground, animals drink water or
eat other organisms which are composed
mostly of water.
3. Release – Plants transpire, animals
breathe and expel liquid wastes.

3. Water is essentially required for
different life forms such as plants
animals, Birds etc. For cell building and
other purposes.
The main source for the water is ocean.
The water from the oceans is
evaporated, clouds are formed and
carried away by wind and they
precipitate.

4.  The water received from precipitation
is lost to the ocean back by different
processes such as run- off from soil,
evaporation from lakes, ponds,
streams and transpiration from plant.
 The water which is absorbed in the
ground is also lost by direct or indirect
way to the ocean
For example, some water which
is absorbed in ground is utilized by
plants and then evaporated.

5. The ground water flows to the
streams and the stretch finally lost
in the oceans etc. Thus, we find
that there is a constant circulation
of water from oceans to the air and
back again to the oceans.
This process has not end
beginning and therefore it is
termed as hydrological cycle or
water cycle.

6. Hydrological Cycle
1

7. Evaporation and transpiration
Condensation and formation of cloud:
Rising air current all the vapor up into the atmosphere cool
 formation of cloud cloud is made up of droplet of
water
Precipitation: Snow or rain fall
Run off and collection of under ground water
Infiltration and percolation

8.  The hydrological cycle can be briefed by the following
equation.
P = ET + DST + S
The total amount of water present on the earth surface
remains constant but undergoes continuous transformation
from water vapor to liquid.
This equation is also called as water balance equation.
Where, P : Water received by precipitation,
ET : Loss by evapotranspiration,
DST : The gain on loss by storage in the soil
S : The surplus run-off of water
From this mathematical relation, we can find out the value
of other elements.

9. It can be defined as earthward falling of
water drops or ice particles that have
formed by rapid condensation in the
atmosphere.
Forms of Precipitation
A. Liquid form B. Solid form C. Mixed form
1. Rain 1. Snow 1. Sleet
2. Drizzle 2. Hail 2 Hail storm
3. Shower

10. 1. Rain:
• Rain is defined as precipitation of drops of
liquid water. The clouds consists of minutes
of minutes droplets of water of about 0.02
mm diameter.
• When these minute water droplets in
clouds combine and form large drops that
become so large that they can not remain
suspended in the air and they fall down as
rain.
•
A. Liquid Form

11. •The droplets are formed by repaid
condensation. The rain drops have diameters
ranging from 0.05 to 0.06 cm (0.5 to 0.6 mm)
• The line joining the places of equal rainfall
called Isohyets.
2

12. Types of Rain:
I) Convectional rains:
Due to heating, the air near the ground becomes hot
and light and starts upward movement (This is known
as convection.) as air moves upward it cools at the
DALR (dry adiabatic lapse rate) (9.8 °C/km) and
becomes saturated (having RH 100%) and dew point
is reached where the condensation. This level or
height is known as condensation level.
Above condensation level air cools at SALR
(Saturated Adiabatic Lapse Rate) (5 °C/km) clouds are
formed. Then further condensation results into
precipitation. These rains are known convectional
rains.

13. 3

14. II) Orographic or relief rains:
When the moist air coming from sea encounters
mountain or relief barrier, it can not move horizontally
and has to overcome mountain.
When this air rises upward, coolsdown, cloud is
formed and condensation starts and giving
precipitation. These rains are known as orographic
rains thus high rains are possible on the windward
side of the mountain.
After crossing the mountain divide, when air descends
downward, the air is compressed and it warmed up at
DALR (dry adiabatic lapse rate). This warm air does
not give any precipitation on the leeward region. This
is known as rain shadow region.

15. 4

16. III) Cyclonic /Frontal and Convergent rains:
Frontal precipitation is produced when two opposing air
currents with different temperature meet, vertical lifting
takes place which gives rise to condensation and
precipitation.
When the humus and warm air mass meets the cold air
mass, the colder air being denser tends to push below
the warmer air and replace it.
The boundary zones along which two air masses meet
are called as fronts. When the mixing of warm and
moist air with cold air mass takes place, the
temperature of the warm and air falls down, saturation
occurs and may give precipitation and it also
responsible for cyclone formation and rains received
from cyclones are called cyclonic reins.

17. 5

18. 2) Drizzle:
It is more or less uniform precipitation of very small
and numerous raindrops which are carried away
even by light wind. The drizzle drop is less than
0.5 mm in size, and precipitate at the rate usually
less than 1 mm per hour.
6

19. 3) Shower:
Precipitation lasting for a short time with relatively
clear intervals is called shower. This occurs from
the passing clouds.
7

20. 1. Snow:
Snow is defined as precipitation of water in the
solid form of small or large ice crystals.
It occurs only when the condensing medium has a
temperature below freezing temperature, snow is
generally in the form of individual crystals or in
flakes that are aggregates of many crystals.
Snow flakes are formed
in high clouds.
Snow is measured with
snow gauge.
B) Solid Form:
8

21. 2. Hail:
Hail is a precipitation of solid ice. On a
warm sunny day, a strong Connective column
may cause the formation of pellets having
spherical Shape and concentric layers of ice.
Such a formation is known as hail.
9

22. 1. Sleet
Simultaneous precipitation of the
mixture of rain and snow is called as
sleet.
C. Mixed Form:
10

23. 2. Hailstorm:
Rainfall associated with hail stones is
called hailstorm.
1211

24. The atmosphere is a cloud of gas and suspended
solids extending from the Earth's surface out
many thousands of miles, becoming increasingly
thinner with distance but always held by the
Earth's gravitational pull.
The atmosphere is made up of layers. it surrounds
the Earth and holds the air we breathe; it protects
us from outer space; and holds moisture (clouds),
gases, and tiny particles. In short, the atmosphere
is the protective bubble we live in.

25.  This protective bubble consists of several
gases with the top four making up 99.998%
of all gases. of the dry composition of the
atmosphere nitrogen, by far, is the most
common.
 Nitrogen dilutes oxygen and prevents rapid
burning at the Earth's surface. Living things
need it to make proteins.
 Oxygen is used by all living things and is
essential for respiration.

26. Gas Name Chemical Formula Percent Volume
Nitrogen N2 78.08%
Oxygen O2 20.95%
*Water H2O 0 to 4%
Argon Ar 0.93%
*Carbon Dioxide CO2 0.0360%
Neon Ne 0.0018%
Helium He 0.0005%
*Methane CH4 0.00017%
Hydrogen H2 0.00005%
*Nitrous Oxide N2O 0.00003%
*Ozone O3 0.000004%

27. Thermosphere
13

28. On the basis of the vertical temperature
difference, the atmosphere can be divided
into four horizontal layers or shells, namely.
A) Lower Atmosphere:
1. Troposphere
2. Stratosphere
B) Upper Atmosphere:
1. Mesosphere
2. Thermosphere
14

29. 1. Troposphere:
The altitude of the troposphere changes
according to latitude.
It has an elevation of about 16 km at the
equator and only 8 km at the poles. Its
average altitude is about 11 km.
It contains near about 75% of the gaseous
mass of the total atmosphere, water vapor
and aerosols. It is the realm of clouds,
storm and convective motion.
A) Lower Atmosphere:

30. The outstanding characteristic of the
troposphere is the filmy uniform degree in
temperature with increase in altitude until
minimum temperature of -50 to -60 °C is
reached.
The isothermal layer marking the end of
temperature decrease is called tropopause
and it separates troposphere and
stratosphere.
Through out the troposphere there is a
general decrease of temperature with
increase in height at a minimum rate of
about 6.5 °C/km or 3.6 °F/1000 ft.

31. 2. Stratosphere:
 This is the second atmospheric layer above
tropopause which extends upwards about 50 km.
 The stratosphere contains much of the total
atmospheric ozone. The density of ozone is
maximum at 22 to 24 km height approximately.
 The ozone at the upper layer of this sphere absorbs
the ultraviolet rays from the Sun and temperature
may exceed 0 °C.
 In stratosphere the temperature increases with
increase in height.

32. 1. Mesosphere:
This is the third layer of atmosphere. A thin
isothermal layer called a stratopause is the
boundary layer, which separates stratosphere and
mesosphere.
Above the warm stratopause, temperature
decreases with increase in height to a minimum of
about -90 °C at about 80 km height.
Pressure in this layer is very low and decreases
from 1 Mb at about 50 km to about 0.01 mb at 80
km nearly. The thin isothermal layer, which
separates mesosphere from thermosphere, is
called mesopause.
B) Upper Atmosphere:

33. 2. Thermosphere:
 Outermost shell is known as thermosphere. It lies
above 80 km height .
 In this sphere the atmospheric densities are
extremely low.
 In this sphere temperature increases with increase
in height due to absorption of ultraviolet radiation
from the Sun. Probably it reaches to 950 °C at 350
km to 1700 °C at an underfined upper limit but
these temperatures are essentially theoretical.

34. Definition:
The air that moves parallel to any part of the
earth surface is called wind or The air
moving horizontally on the surface of the
earth is known as wind.
Air Current:
Vertically or nearly vertical movements of air
resulting from convection ,turbulence or any
other cause is known as air current.

35. Calm air
These are generally felt as an airy condition. It
is also called light wind, and it has a speed of about
1km/hr.
Calm air will be noticed by smoke rising
vertically from a chimney. They have a Beaufort
Number 0.
Gentle Breeze
Gentle breezes have speeds of about 12-
20km/hr. Leaves and small twigs would be constantly
moving with gently breezes. They have a Beaufort
Number 3.

36. Moderate winds
Moderate winds have speeds of about 20-
38km/hr. They are enough to fly a kite and keep it
going higher and higher. They can cause
moderate waves with whitecaps on the sea and
make trees whistle.
Strong winds
Strong winds have speeds of about 62-74km/hr.
They can cause high waves over the seas and
break off twigs and small branches from trees.
They have a Beaufort number of 8.

37. Gale winds
Gale winds have speeds of about 75km/hr and
more. They can be very destructive and they carry
lots of broken branches and twigs from trees.
They cause high tidal waves and rolling seas.
They can also rip off roofs of building.
15

38. Cloud:
Cloud can be defined as a mass of tiny
water droplets ice crystals OR both
condensed on hygroscopic nuclei and
suspending in the atmosphere.
Clouds and fogs are composed of water
droplets or ice crystals or both of the
order of size 20 to 60 microns (0.008 -
0.024 millimeter).

39. Isoneph:
Lime joining places of equal clouds cover on a
map is known as isoneph.
Principles of cloud classification :
The great variety of cloud forms necessitates a
classification of weather reporting. The
internationally adopted system is based upon (a)
The general shape; structure and vertical extend
of the clouds and (b) their altitude.

40. 1. Cirrus (CI):
Meaning “cur” and is recognized by its veil, like
fibrous or featery form. It is the highest type of
cloud, ranging from approximately 7-12 km in
altitude. (20,000 to 35,000 feet).
16

41. 2. Cumulus (Cu):
Meaning “heap”, is the wooly, bundly cloud with
rounded top and flat base. It is the most common in
the summer season and in latitudes where high
temperature prevail and it always results from
convection Its height is variable and depends on
relative humidity of the air.
17

42. 3. Stratus (St):
It is a sheet type cloud without any form to
distinguish it. It is usually lower than cumulus.
18

43. 4. Nimbus (Nb):
It is any dark and ragged cloud and from which
precipitation occurs.
19

44. Cloud
family
and
Height
Name of
cloud and
abbreviatio
n
Composition Possible weather
change
Description and appearance
1 2 3 4 5
Family A
High
clouds
7 to 12
km
1 Cirrus (Ci) Ice crystals
May Indicate storm
showery weather
It is wispy and feathery, sun shines
without shadow. It does not
produce precipitations
2.
Cirrocumulu
s (CC)
Ice crystals Possible storm
Meekerel sky, often fore renners of
cyclone, look like sippled sand
3.
Cirrostratus
(Cs)
Ice crystals Possible storm
Meekeral sky, often fore runners of
cyclone, look like sippled sand.
Family
B
middle
clods
3-7 km
4.
Altocumulus
(As)
Ice & water
Steady rain or
snow
Looks like wool peak, sheep bulk
clouds.
5.
Atmostratus
(As)
Water and ice
Impending rain or
snow
Fibrous veil or sheet, grey or
bluish, produce coronos, usually
ct.st shadow.

45. Family C
low
clouds
from
ground
to 2-3 km
6.
Stratocumulus
(Se)
Water Rain possible
Long parallel rolls, pushed
together or broken masses which
look soft and grey but with darker
parts, air is smooth above but
strong updrafts occur below.
7.
straus (St)
Water
May produce
drizzle
A low uniform layer, resembling
fog, but resting not on the ground,
chief winter cloud.
8.
Nimbostrauts
Water or
Ice
Impending rain
or snow
Fibrous veil or sheet, grey, grey
or bluish produce coronas,
usually
Family D
clouds
with
vertical
develop
ment
from
0.5 to 16
km
9.
Cumu-lus (Cu)
Water Fair weather
Looks like wool pack, dark below due
to shadow, may develop into
cumulous –Nimbus flat base.
10.
Cumulous –
Nimbus (Cb)
Ice in upper
level and
water in
lower level.
Violet winds rain,
all possible
thunderstorm hail
lighting possible
Thunder head, towering anvil top,
violet up and down drafts, aviators
avoid them, develop from cumulus,
chief precipitation makers.

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