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: skarmakar@iitb.ac.in Ph. # +91 22 2576 7857
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.
Topics to be covered Weather Introduction to Hydrology Different stages of Hydrology or water cycle Hydrologic losses and measurements Analytical Methods Empirical 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 activity, whereas climate is the term for the average atmospheric conditions over longer periods of time. Lecture 1 (Wikipedia)
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. Lecture 1 (http://www.windows.ucar.edu/tour/link=/earth/atmosphere/layers_activity_print.html)
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) Lecture 1
Lecture 1 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.
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. Lecture 1
Frontal lifting Lecture 1
Lecture 1 Orographic lifting
Lecture 1 Convectional lifting (climateofindia.pbworks.com)
Lecture 1 Cyclonic lifting
Lecture 1 Factors affecting Indian climate Factors affecting Indian climate Related to Location and Relief Latitude Altitude Relief Distance from Sea The Himalayan Mountains Distribution of Land & water Related to Air Pressure and Wind Surface pressure & wind Upper air circulation Western cyclones
Seasons Cold weather Hot weather South west monsoon Retreating monsoon Lecture 1
Seasons Cold Weather Season 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 Lecture 1
Seasons Temperature-January 15 0 C 10 0 C` 20 0 C 25 0 C 20 0 C 20 0 C 20 0 C 25 0 C Lecture 1 (climateofindia.pbworks.com)
Seasons Pressure-January HIGH PRESSURE 1014 Lecture 1 (climateofindia.pbworks.com)
Seasons Winter Rainfall RAINFALL DUE TO WESTERN DISTURBANCES RAINFALL DUE TO NORTH EAST WIND Lecture 1
Seasons Hot Weather Season 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. May 48 0 C April 38 0 C March 30 0 C Lecture 1
Seasons Temperature-July 25 0 C 30 0 C Lecture 1
Seasons Pressure-July Lecture 1
Seasons Storms in Hot Weather Season BARDOLI CHHEERHA LOO KALBAISAKHI MANGO SHOWER Lecture 1 BLOSSOM SHOWER (climateofindia.pbworks.com)
Lecture 1 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.
Lecture 1 Seasons Monsoon Wind Arabian sea Branch Bay of Bengal Branch INTER TROPICAL CONVERGENCE ZONE
Lecture 1 Seasons Onset of SW Monsoon
Lecture 1 Seasons Retreating Monsoon Season 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. LOW PRESSURE Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive. This is commonly known as the October heat
Lecture 1 Seasons Withdrawal of Monsoon
Seasons Distribution of Rainfall > 200cm 100-200cm 50-100 cm < 50cm Lecture 1 (climateofindia.pbworks.com)
Lecture 1 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.