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Transcript of M1 lecture1
Advanced Hydrology(Web course)
Subhankar KarmakarAssistant Professor
Centre for Environmental Science and Engineering (CESE)Indian Institute of Technology Bombay
Powai, Mumbai 400 076Email: [email protected]
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