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:
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.
Topics to be covered
Weather
Introduction to Hydrology
Different stages of Hydrology or water cycle
Hydrologic losses and measurements
Analytical Methods
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
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.
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
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.
Module 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
Frontal lifting
Module 1
Convectional lifting
(climateofindia.pbworks.com)
Module 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
Seasons
Cold weather
Hot weather
South west monsoon
► It extends from December to February.
► Vertical sun rays shift towards southern hemisphere.
► North India experiences intense cold
► Light wind blow makes this season pleasant in south India.
► Occasional tropical cyclone visit eastern coast in this
season. Tropical Cyclone
Cold Weather Season
Seasons
Module 1
250C 250C
200C 200C
200C 150C
200C
100C`
Temperature-January
Pressure-January
(climateofindia.pbworks.com)
1014
HIGH PRESSURE
Module 1 Seasons
RAINFALL DUE TO WESTERN DISTURBANCES
RAINFALL DUE TO NORTH EAST
WIND
Winter Rainfall
► 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
Temperature-July
250C
300C
Pressure-July
Module 1 Seasons
LOO
KALBAISAKHI
BARDOLI CHHEERHA
MANGO SHOWER
Storms in Hot Weather Season
► 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
INTER TROPICAL CONVERGENCE ZONE Arabian
sea Branch
Bay of Bengal Branch
Monsoon Wind
Onset of SW Monsoon
Module 1 Seasons
► 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
Withdrawal of Monsoon
Module 1 Seasons
> 200cm
100-200cm
50-100 cm
Distribution 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.
Variability of Rainfall
Module 1 Seasons
