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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
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Hydrologic Cycle
Prof. Subhankar KarmakarIIT Bombay
Module 1
3 Lectures
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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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Lecture 1: Weather and hydrologic cycle
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Weather & Climate
Weather- the state of the atmosphere with respect to heat or cold, wetness
ordryness, calmorstorm, clearness or cloudiness.
Cl imate the average course or condition of the weather ata 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 precipitationactivity, whereas climate is the term for the average atmospheric conditionsover longer periods of time.
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Atmosphere
Troposphere
Most of the weather occurs.
Stratosphere
19% of the atmospheres gases;
Ozone layer
Mesosphere
Most meteorites burn up here.
Thermosphere
High energy rays from the sun areabsorbed;
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
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Winds and Wind belts
Exist to circulate heat and
moisture from areas of heating
to areas of coolingEquator 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 inthe atmosphere and located atsome altitude above the earths surface.
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Classif ication 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 its the reason why windward slopes
receive more precipitation).
Convective Lift ing:
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 cl imate
Related to Locat ion and Rel ief Related to Air Pressure and Wind
Latitude
Al titude
Relief
Distance from Sea
The Himalayan Mountains
Distribut ion of Land & water
Surface pressure & wind
Upper air circulation
Western cyclones
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Factors affecting Indian climate
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Seasons
Cold weather
Hot weather
South west monsoon
Retreating monsoon
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It extends from December toFebruary.
Vertical sun rays shift towardssouthernhemisphere.
North India experiencesintense cold
Light wind blow makes thisseason pleasant in south
India.
Occasional tropical cyclonevisit eastern coast in thisseason.
Tropical Cyclone
Cold Weather Season
Seasons
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250C
250C
200C
200
C
200C
150C
200C
100C`
Temperature-January
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Seasons
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Pressure-January
(climateofindia.pbworks.com)
1014
HIGHPRESSURE
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Seasons
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RAINFALL DUE
TO WESTERN
DISTURBANCES
RAINFALL DUE
TO NORTH EAST
WIND
Winter Rainfall
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Seasons
Lecture 1
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It extends from March toMay.
Vertical sun rays shifttowards Northern
hemisphere.
Temperature rises graduallyfrom south to north.
Highest Temperature
experiences in Karnataka inMarch, Madhya Pradesh inApril and Rajastan in May. March 300C
Apri l 380C
May 480C
Hot Weather Season
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Seasons
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Temperature-July
250C
300C
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Seasons
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Pressure-July
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Seasons
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LOO
KALBAISAKHI
BARDOLI
CHHEERHA
MANGO
SHOWER
BLOSSOM
SHOWER
Storms in Hot Weather Season
(climateofindia.pbworks.com) Module 1
Seasons
Lecture 1
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It extends from J une toSeptember.
Intense heating in northwest India creates low
pressure region.
Low pressure attract thewind from the surroundingregion.
After having rains for a fewdays sometime monsoonfails to occur for one ormore weeks is known asbreak in the monsoon.
South West Monsoon
LOW PRESSURE
HIGH TEMPERATURE
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Seasons
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INTER TROPICAL CONVERGENCE ZONE
Arabiansea Branch
Bay ofBengal
Branch
Monsoon Wind
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Seasons
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Onset of SW Monsoon
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Seasons
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It extends from October toNovember
Vertical sun rays start shiftingtowards Northernhemisphere.
Low pressure region shiftfrom northern parts of Indiatowards south.
Owing to the conditions ofhigh temperature andhumidity, the weatherbecomes rather oppressive.
This is commonly known asthe October heat
LOW PRESSURE
Retreating Monsoon Season
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Seasons
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Withdrawal of Monsoon
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> 200cm
100-200cm
50-100 cm
< 50cm
Distr ibut ion of Rainfall
(climateofindia.pbworks.com) Module 1
Seasons
Lecture 1
Seasons
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The variability of rainfall is computedwith the help of the following formula:C.V.= Standard Deviation/ Mean * 100
Variability 50% found in Western
Rajastan, J & K and interior parts ofDeccan.
Region with high rainfall has lessvariability.
Variability of Rainfall
Seasons