Advanced Hydrology(Web course)

Subhankar KarmakarAssistant Professor

Centre for Environmental Science and Engineering (CESE)Indian Institute of Technology Bombay

Powai, Mumbai 400 076Email: skarmakar@iitb.ac.in

Ph. # +91 22 2576 7857

Hydrologic Cycle

Prof. Subhankar KarmakarIIT Bombay

Module 13 Lectures

The objective of this module is to introduce the

phenomena of weather, different stages of the hydrologic

cycle, hydrologic losses and its measurements.

Module 1

Topics to be covered

Weather

Introduction to Hydrology

Different stages of Hydrology or water cycle

Hydrologic losses and measurements

Analytical Methods

Empirical Methods

Module 1

Lecture 1: Weather and hydrologic cycle

Module 1

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”.

(Wikipedia)

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.

Module 1Lecture 1

Atmosphere

Troposphere Most of the weather occurs.

Stratosphere19% 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.

(http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/layers_activity_print.html) Module 1Lecture 1

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)

Module 1Lecture 1

Cloud Types

Cloud is a visible set of drops of water and fragments of ice suspended inthe atmosphere and located at some altitude above the earth’s surface.

Module 1Lecture 1

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.

Module 1Lecture 1

Frontal lifting

Module 1Lecture 1

Orographic lifting

Module 1Lecture 1

Convectional lifting

(climateofindia.pbworks.com)

Module 1Lecture 1

Cyclonic lifting

Module 1Lecture 1

Factors affecting Indian climate

Related to Location and Relief Related to Air Pressure and Wind

•Latitude

•Altitude

•Relief

•Distance from Sea

•The Himalayan Mountains

•Distribution of Land & water

•Surface pressure & wind

•Upper air circulation

•Western cyclones

Module 1

Factors affecting Indian climate

Lecture 1

Module 1

Seasons

Cold weather

Hot weather

South west monsoon

Retreating monsoon

Lecture 1

► It extends from December toFebruary.

► Vertical sun rays shift towardssouthern hemisphere.

► North India experiencesintense cold

► Light wind blow makes thisseason pleasant in southIndia.

► Occasional tropical cyclonevisit eastern coast in thisseason.

Tropical Cyclone

Cold Weather Season

Seasons

Module 1Lecture 1

250C

250C

200C

200C200C

150C

200C

100C`

Temperature-January

(climateofindia.pbworks.com) Module 1

Seasons

Lecture 1

Pressure-January

(climateofindia.pbworks.com)

1014

HIGH PRESSURE

Module 1

Seasons

Lecture 1

RAINFALL DUE TO WESTERN

DISTURBANCES

RAINFALL DUE TO NORTH EAST

WIND

Winter Rainfall

Module 1

Seasons

Lecture 1

► It extends from March to May.

► Vertical sun rays shift towards Northern hemisphere.

► Temperature rises gradually from south to north.

► Highest Temperature experiences in Karnataka in March, Madhya Pradesh in April and Rajastan in May. March 300C

April 380C

May 480C

Hot Weather Season

Module 1

Seasons

Lecture 1

Temperature-July

250C

300C

Module 1

Seasons

Lecture 1

Pressure-July

Module 1

Seasons

Lecture 1

LOO

KALBAISAKHI

BARDOLI CHHEERHA

MANGO SHOWER

BLOSSOM SHOWER

Storms in Hot Weather Season

(climateofindia.pbworks.com) Module 1

Seasons

Lecture 1

► 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.

► After having rains for a few days sometime monsoon fails to occur for one or more weeks is known as break in the monsoon.

South West Monsoon

LOW PRESSURE HIGH TEMPERATURE

Module 1

Seasons

Lecture 1

INTER TROPICAL CONVERGENCE ZONE

Arabian sea Branch

Bay of Bengal Branch

Monsoon Wind

Module 1

Seasons

Lecture 1

Onset of SW Monsoon

Module 1

Seasons

Lecture 1

► It extends from October to November

► Vertical sun rays start shifting towards Northern hemisphere.

► 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’

LOW PRESSURE

Retreating Monsoon Season

Module 1

Seasons

Lecture 1

Withdrawal of Monsoon

Module 1

Seasons

Lecture 1

> 200cm

100-200cm

50-100 cm

< 50cm

Distribution of Rainfall

(climateofindia.pbworks.com) Module 1

Seasons

Lecture 1

► 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.

Variability of Rainfall

Module 1

Seasons

Lecture 1