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Advanced Hydrology
(Web course)
Subhankar Karmakar
Assistant Professor
Centre for Environmental Science and Engineering (CESE)
Indian Institute of Technology Bombay
Powai, Mumbai 400 076
Email: [email protected]
Ph. # +91 22 2576 7857
Module 1
3 Lectures
Hydrologic Cycle
Prof. Subhankar Karmakar
IIT Bombay
The objective of this module is to introduce the
phenomena of weather, different stages of the hydrologic
cycle, hydrologic losses and its measurements.
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Topics to be covered

Weather
 Introduction to Hydrology
 Different stages of Hydrology or water cycle
 Hydrologic losses and measurements
 Analytical Methods
Empirical Methods
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Module 1
Lecture 1: Weather and hydrologic cycle
Weather & Climate
 Weather- “the state of the atmosphere with respect to heat or cold, wetness
or dryness, calm or storm, clearness or cloudiness”.
 Climate – “the average course or condition of the weather at a place usually
over a period of years as exhibited by temperature, wind velocity, and
precipitation”.
Weather refers, generally, to day-to-day temperature and precipitation
activity, whereas climate is the term for the average atmospheric conditions
over longer periods of time.
(Wikipedia)
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Atmosphere
Troposphere
 Most of the weather occurs.
Stratosphere
19% of the atmosphere’s gases;
 Ozone layer
Mesosphere
Most meteorites burn up here.
Thermosphere
 High energy rays from the sun are
absorbed;
 Hottest layer.
Exosphere
Molecules from atmosphere
escape into space; satellites orbit here.
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(http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/layers_activity_print.html)
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Winds and Wind belts
 Exist to circulate heat and
moisture from areas of heating
to areas of cooling
Equator to poles
Low altitudes to high
altitudes
 Three bands of low and high
pressure above and below the
equator (area of low pressure)
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Cloud Types
Cloud is a visible set of drops of water and fragments of ice suspended in
the atmosphere and located at some altitude above the earth’s surface.
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Classification of Precipitation events
 Based on the “mechanism” by which air is lifted.

Frontal lifting:
Warmer air is forced to go above cooler air in equilibrium with a cooler surface.

Orographic lifting:
Air is forced to go over mountains (and it’s the reason why windward slopes
receive more precipitation).

Convective Lifting:
Warm air rises from a warm surface and progressively cools down.

Cyclonic Lifting:
A cyclonic storm is a large, low pressure system that forms when a warm air
mass and a cold air mass collide.
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Frontal lifting
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Orographic lifting
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Convectional lifting
(climateofindia.pbworks.com)
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Cyclonic lifting
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Factors affecting Indian climate
Factors affecting Indian climate
Related to Location and Relief
Related to Air Pressure and Wind
•Latitude
•Surface pressure & wind
•Altitude
•Upper air circulation
•Relief
•Western cyclones
•Distance from Sea
•The Himalayan Mountains
•Distribution of Land & water
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Seasons
Cold weather
Hot weather
South west monsoon
Retreating monsoon
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Seasons
Cold Weather Season
► It extends from December to
February.
► Vertical sun rays shift towards
southern hemisphere.
► North
India
intense cold
experiences
► Light wind blow makes this
season pleasant in south
India.
► Occasional tropical cyclone
visit eastern coast in this
season.
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Tropical Cyclone
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Seasons
Temperature-January
100C`
150C
200C
200C
250C
200C
200C
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250C
(climateofindia.pbworks.com)
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Seasons
Pressure-January
HIGH
PRESSURE
1014
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(climateofindia.pbworks.com)
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Seasons
Winter Rainfall
RAINFALL DUE
TO WESTERN
DISTURBANCES
RAINFALL DUE
TO NORTH EAST
WIND
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Seasons
Hot Weather Season
► It extends from March to
May.
► Vertical sun rays shift
towards Northern
hemisphere.
May 480C
► Temperature rises gradually
from south to north.
► Highest Temperature
experiences in Karnataka in
March, Madhya Pradesh in
April and Rajastan in May.
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April 380C
March 300C
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Seasons
Temperature-July
250C
300C
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Seasons
Pressure-July
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Seasons
Storms in Hot Weather Season
BARDOLI
CHHEERHA
LOO
KALBAISAKHI
MANGO
SHOWER
BLOSSOM
SHOWER
Lecture 1
(climateofindia.pbworks.com)
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Seasons
South West Monsoon
► It extends from June to
September.
► Intense heating in north
west India creates low
pressure region.
► Low pressure attract the
wind from the surrounding
region.
LOW PRESSURE
HIGH TEMPERATURE
► After having rains for a few
days sometime monsoon
fails to occur for one or
more weeks is known as
break in the monsoon.
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Seasons
Monsoon Wind
Arabian
sea Branch
Bay of
Bengal
Branch
INTER TROPICAL CONVERGENCE ZONE
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Seasons
Onset of SW Monsoon
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Seasons
Retreating Monsoon Season
► It extends from October to
November
► Vertical sun rays start shifting
towards Northern
hemisphere.
LOW PRESSURE
► Low pressure region shift
from northern parts of India
towards south.
► Owing to the conditions of
high temperature and
humidity, the weather
becomes rather oppressive.
This is commonly known as
the ‘October heat’
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Seasons
Withdrawal of Monsoon
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Seasons
Distribution of Rainfall
> 200cm
100-200cm
50-100 cm
< 50cm
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(climateofindia.pbworks.com)
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Seasons
Variability of Rainfall
► The variability of rainfall is computed
with the help of the following formula:
C.V.= Standard Deviation/ Mean * 100
► Variability  <25% exist in Western
coasts, Western Ghats, north-eastern
peninsula, eastern plain of the
Ganga, northern-India, Uttaranchal, SW
J & K & HP.
► Variability  >50% found in Western
Rajastan, J & K and interior parts of
Deccan.
► Region with high rainfall has less
variability.
Lecture 1
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