Applied Hydrometeorology Applied Hydrometeorology

By Pukh Raj Rakhecha Formerly at Indian Institute of Tropical Meteorology, Pune, India

and

Vijay P. Singh Department of Biological and Agricultural Engineering and Department of Civil & Environmental Engineering Texas A & M University, College Station, USA A C.I.P. Catalogue record for this book is available from the Library of Congress.

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Printed in India. Dedicated to Our families Wife Anusuya, sons Ashok Kumar and Ramesh —Pukh Raj Rakhecha Wife Anita, son Vinay, daughter-in-law Sonali and daughter Arti —Vijay P. Singh About the Authors

Dr. Pukh Raj Rakhecha, former Dy. Director (Hydrometeorology) with the Indian Institute of Tropical Meteorology in Pune has worked on a variety of hydrometeorological projects including studies of design rainfalls, rainfall statistics, river basin PMP analysis, IFD relations in engineering design, major rainstorms analysis, floods and drought studies, water balance studies and rainfall runoff relations. He has over 250 research papers to his credit and has been consultant on numerous hydrometeorolgical studies. Dr. Rakhecha has travelled widely visiting Australia, Sweden, Switzerland, England, Malaysia, Japan, Iceland and United States for research work and participation in international conferences. He is an internationally recognised hydrometeorologist on PMP studies and member of several scientific societies including International Association of Hydrological Sciences (IAHS). Dr. Vijay P. Singh holds the Caroline & William N Lehrer Distinguished Chair in Water Engineering, is Professor of Civil and Environmental Engineering, and Professor of Biological and Agricultural Engineering at Texas A & M University. He has published more than 450 journal articles, 70 book chapters, 240 conference proceeding papers, and 70 technical reports and bulletins; authored or co-authored fourteen books and has edited another forty-five texts. Prof. Singh has made pioneering contributions in the application of systems analysis, kinematic wave theory, and entropy theory to a range of problems in hydraulics, water quality engineering, irrigation, hydrology and water resources. Prof. Singh has been the recipient of the ASCE Arid Land Hydraulic Engineering Award (2002) and the Ven Te Chow Award (2005), and most recently the AIH Ray K. Linsley Award for outstanding contributions to surface water hydrology. He has served as Editor- in-Chief of the Water Science and Technology (WST) series for Springer, and also currently serves as Editor-in-Chief of the ASCE Journal of Hydrologic Engineering and Editor-Chief of Water Science and Engineering. He has directed the organization of 17 international conferences, chaired more than 40 conference sessions, given more than 35 keynote addresses, and examined more than 40 PhD. candidates abroad. Preface

Water is vital for life. Since the dawn of civilization, much effort has been made to harness sources of fresh water. Recent years have raised global awareness of the need for increasing demand of water worldwide, largely because of growing population, rising standard of living, higher demand for energy, and greater appreciation for environmental quality. As an example, the world population has increased threefold in the past five decades. In order to meet the rising water demand, water resources are being developed by building large dams, reservoirs, barrages and weirs across rivers worldwide. The guiding principle for water resources development has been to ensure adequate supply of water for agriculture, domestic use (including fine drinking water), waste disposal, industries, and energy production, with due attention to maintain the ecosystem functions. This development, however, depends on a holistic, cooperative and scientific approach. The basic inputs in the assessment of water resources for a given region are from hydrological data and the subject of hydrology forms the core in achieving sustainable development of water resources. Barring a few exceptions, hydrological data for most river basins are sparse and therefore it is difficult to comprehensively assess their water resources. The major source of water is rainfall which occurs as a result of condensation of atmospheric moisture governed by the science of meteorology. Rainfall, therefore, is the principal meteorological element whose recording with other meteorological elements, such as temperature, humidity, wind, and so on, was initiated a long time ago. That is why good networks of raingauge stations have been in existence for several decades in many countries of the world, and long rainfall records are not uncommon these days. Meteorologists, hydrologists and engineers have long recognized the value of hydro- meteorological data and more importantly the rainfall data for hydrologic analyses. Thus, application and analysis of meteorological data for the solution of hydrologic problems has precisely come to be known as the science of viii Preface hydrometeorology. In a broad sense, hydrometeorology is a border line science linking meteorology—the science of atmosphere—with hydrology—the science of water of the earth and earth’s atmosphere. In engineering hydrology dealing with design and operation of water resource projects, the subject of hydrometeorology occupies a central position. Obviously, the importance of the subject of hydrometeorology has become increasingly recognized and it is now studied not only by hydrologists and engineers but also by students from many different disciplines. Realizing the importance of the subject, there is a need for a textbook like the present one on applied hydrometeorology oriented towards the Asian environment, particularly to India, which can provide a complete set of tools to practicing engineers and hydrologists engaged in the planning, development and management of water resources. This constitutes the primary objective of this book. The emphasis in the book is on the practical applications of meteorology for water resources development and understanding of the needed meteorological concepts. The subject matter of the book follows this rationale. The book contains 15 chapters encompassing a wide spectrum of topics of hydrometeorology. Chapter 1 scopes out the area of hydrometeorology, and deals with meteorological variables and their use in hydrology, hydrological cycle, global distribution of land and water, and global water budget. Chapter 2 discusses the earth-atmospheric system. Included in the discussion are composition of the atmosphere, mass of atmosphere and hydrosphere, vertical structure of atmosphere, air density and its variation, hydrostatic equation, hydrostatics of special atmosphere, reduction of pressure to sea level, and atmospheric stability. The discussion of meteorological processes, constituting the subject matter of Chapter 3, includes compression and expansion of gases, forms of heat, equation of state for a perfect gas, isothermal and adiabatic changes, the first law of thermodynamics, adiabatic process, vertical motion in the atmosphere, mixture of gases, equation of state of moist air, and precipitable water. Chapter 4 deals with radiation and temperature. Beginning with a discussion of the source of heat and light, it goes on to discuss different aspects of radiation, mean annual heat balance, non-radiative heat exchange between the earth and the troposphere, heat balance, and temperature zones. Weather systems for precipitation are discussed in Chapter 5. Included in the discussion are pressure belts; wind systems of the earth; and scales of weather systems including planetary scale, synoptic scale, and meso scale of weather systems. Chapter 6 deals with weather and precipitation in India. The discussion in the chapter includes location and area, land forms, river basins, and seasons of India; climate controls; rainfall and runoff of continents; seasonal variation of pressure and temperature; onset and withdrawal of monsoons; weather systems affecting Indian rainfall; history of rainfall measurement in India; rainfall over India; assessment of rainwater resources; and present status of water utilization in India. Preface ix

Defining and classifying tropical disturbances and hurricanes, Chapter 7 discusses major hurricanes and super typhoons, wind rotation, conversion of wind speeds, formation of tropical storms, frequency of hurricanes for oceanic regions, absence of hurricanes in South Atlantic Ocean, naming hurricanes, life cycle of hurricanes, structure of hurricanes, hurricane climatology, record hurricane, largest rainfall from tropical storms/hurricanes, longest lasting hurricanes, climatic effects of hurricane activity, global warming and hurricanes, hurricane threats, damages and destruction, seeding of hurricanes, and damage caused by cyclones. Greatest point and areal rainfalls constitute the subject matter of Chapter 8. It includes significant point rainfall occurrences over India, China, Australia, and Japan; world’s greatest point rainfalls; importance of greatest areal rainfalls; and greatest areal rainfalls over India, USA, Japan, and China. Recognizing rainfall as an important source of input for water resources, Chapter 9 covers precipitation and its measurement. It also encompasses mechanisms of precipitation, forms of precipitation, types of precipitation, measurement of precipitation, network design, estimation of missing data, mean depth of rainfall over an area, consistency of rainfall records, extension and interpretation of rainfall data, intensity-duration relationships, and point rainfall and areal rainfall relationships. The physical evaluation of probable maximum precipitation (PMP) based on a hydrometeorological procedure is a topic of considerable importance in designing large dams, reservoirs, and spillways and for the derivation of probable maximum floods (PMF). Techniques for estimating the PMP constitute the subject matter of Chapter 9. They discuss rainstorm analysis, depth-area-duration analysis, design storm, data for design storm studies, methods of estimating design storms, probable maximum precipitation, and methods of estimating PMP. Chapter 10 deals with design storm estimation. The material contained in this chapter is of particular value to design engineers. The discussion includes rainstorm and its analysis, depth-area-duration analysis of a rainstorm, design storms, data for design storm studies, methods for estimating design storms, probable maximum precipitation, and methods of estimating PMP. Statistical analysis of precipitation is presented in Chapter 11. It deals with data series for frequency analysis, recurrence interval, calculated risk, frequency analysis, measures of central tendency, measures of variability, skewness, and kurtosis (flattening), moments of frequency distribution, standard frequency distributions, tests of significance, homogeneity of data series, and frequency analysis. Foreshadowing rainfall is covered in Chapter 12. It includes measures of variability, correlation analysis, global scale factors affecting rainfall, types of weather forecasts, techniques for long-range rainfall forecasting in India, Indian summer monsoon and southern oscillation index, statistical techniques used in long range forecasting, multiple regression analysis, and parameters in long-range forecasting of Indian summer monsoon rainfall. x Preface

Chapter 13 deals with evaporation. Beginning with a discussion of the physics of evaporation, it goes on to discuss factors affecting evaporation, measurement of evaporation, evaporation measurement in India, and estimation of evaporation by indirect methods. Extreme hydrometeorological events that arise from unusually high and low precipitation lead to floods and droughts, respectively. These events cause considerable loss of life and property. Droughts constitute the subject matter of Chapter 14. It discusses causes of droughts, evapotranspiration and potential evapotranspiration, types of droughts, droughts in India, El Nino factor relating to droughts, and absence of tropical disturbances and Indian rainfall. The concluding chapter, Chapter 15, is on floods. Defining floods and classifying them, the chapter goes on to discuss the kinds and causes of floods, effects of floods, flood measurements, flood control, estimation of peak floods, flood frequency analysis, floods in Indian rivers, highest floods in India, and comparison of highest floods in India with world’s highest floods. The text material of each chapter contains illustrative examples, which are mostly based on actual, recorded data. It is hoped that the book will be of much use to the professionals engaged in water resources planning, development, and management. Also the book should be useful to university courses concerned with hydrometeorology and its application to water-related issues, as it caters to the requirement of the syllabi of various Indian and foreign universities. There is vast literature on the topics in this book. A comprehensive list of references has been advertently omitted, and only those studies that are deemed most pertinent have been cited. This is because the intended audience would be more interested in applications rather than advanced literature. This, however, in no way reflects a lack of appreciation for the literature. Indeed this book would not have been completed without reviewing the pertinent literature. We have tried to make our acknowledgments as specific as possible. We would be most grateful if readers discovering any discrepancies, errors, or misprints would bring them to our attention. Our families provided unwavering support and help, without which this book would not have been completed. As a small token of our appreciation for their love and support, we dedicate this book to them.

January 2009 Pukh Raj Rakhecha Vijay P. Singh Contents

About the Authors vi Preface vii

1. Introduction 1 1.1 Scope of Hydrometeorology 2 1.2 Meteorological Variables 3 1.3 Earth System 13 1.4 Orbital Motion of Earth and Seasons 13 1.5 Global Distribution of Land and Water 16 1.6 Global Water Budget 17 1.7 Hydrologic Cycle 20 References 23 2. The Atmosphere 24 2.1 Earth-atmosphere System 24 2.2 Composition of the Atmosphere 25 2.3 Mass of the Atmosphere and the Hydrosphere 27 2.4 Average Vertical Structure of Atmosphere 28 2.5 Hydrostatic Equation 30 2.6 Hydrostatics of Special Atmosphere 33 2.7 Reduction of Pressure to Sea Level 36 2.8 Atmospheric Stability and Instability 37 References 38 3. Atmospheric Processes 39 3.1 Heat and Temperature 39 3.2 Compression and Expansion of a Gas 40 3.3 Forms of Heat 40 3.4 Equation of State for a Gas: Perfect Gas 41 xii Contents

3.5 Isothermal and Adiabatic Changes 42 3.6 First Law of Thermodynamics 42 3.7 Vertical Motion in the Atmosphere 44 3.8 Mixture of Gases 47 3.9 Equation of State of Moist Air 48 3.10 Precipitable Water 50 References 53 4. Radiation and Temperature 55 4.1 Sun: The Source of Heat and Light 56 4.2 Radiation 59 4.3 Laws of Radiation 59 4.4 Incoming Solar Radiation without Atmosphere at the Earth’s Surface 61 4.5 Passage of Solar Radiation through Average Atmospheric Condition 63 4.6 Terrestrial Radiation 64 4.7 Mean Annual Heat Balance of the Earth-Atmosphere System 66 4.8 Non-radiative Heat Exchange between the Earth and the Troposphere 67 4.9 Heat Balance 68 4.10 Temperature Zones 68 References 69 5. Weather Systems for Precipitation 71 5.1 Pressure Belts and Wind Systems of the Earth 71 5.2 Scale of Weather Systems 73 5.3 Planetary Scale Weather Systems 74 5.4 Synoptic Scale Weather Systems 76 5.5 Meso Scale Weather Systems 86 5.6 Oceanic Circulation 87 References 88 6. Weather and Precipitation in India 90 6.1 Location and Area of India 90 6.2 Land Forms of India 92 6.3 Climatic Control 92 6.4 River Basins of India 95 6.5 Rainfall and Runoff of Continents 96 6.6 The Seasons of India 96 6.7 Seasonal Variation of Pressure 99 6.8 Mean Seasonal Variation of Air Temperature 102 6.9 Onset and Withdrawal of Monsoons 104 6.10 Main Weather Systems Affecting Indian Rainfall 111 Contents xiii

6.11 History of Rainfall Measurement in India 116 6.12 Rainfall over India 116 6.13 Assessment of Rainwater Resources of India 121 6.14 Present Status of Water Utilization in India 122 References 125 7. Tropical Storms and Hurricanes 126 7.1 Definition 127 7.2 Major Hurricanes and Super Typhoons 129 7.3 Wind Rotation 129 7.4 Formation of Tropical Storms 130 7.5 Origin of Hurricanes 132 7.6 Frequency of Hurricanes for Oceanic Regions 132 7.7 Absence of Hurricanes in South Atlantic Ocean 136 7.8 Naming of Hurricanes 136 7.9 Life Cycle of Hurricanes 138 7.10 Structure of Hurricanes 141 7.11 Hurricane Climatology 143 7.12 Most Intense Hurricanes on Record 151 7.13 Largest Rainfall from Tropical Storms/Hurricanes 152 7.14 Longest Lasting Hurricanes 153 7.15 Climatic Effects of Hurricane Activity 154 7.16 Global Warming and Hurricanes 156 7.17 Hurricane Threats, Damage and Destruction 157 References 161 8. Greatest Point and Areal Rainfalls 163 8.1 Definitions 164 8.2 Significant Rainfall Occurrences over India 164 8.3 Significant Rainfall Occurrences over China 172 8.4 Significant Rainfall Occurrences over Australia 174 8.5 Significant Rainfall Occurrences over Japan 176 8.6 World's Greatest Point Rainfalls 177 8.7 Importance of the Greatest Areal Rainfalls 180 8.8 Greatest Areal Rainfalls over India 181 8.9 Greatest Areal Rainfalls over the USA 186 8.10 Greatest Areal Rainfalls over China 187 8.11 Greatest Areal Rainfalls over Australia 188 References 189 9. Precipitation and Its Measurement 190 9.1 Mechanisms of Precipitation 190 9.2 Forms of Precipitation 191 9.3 Types of Precipitation 192 9.4 Measurement of Precipitation 194 xiv Contents

9.5 Network Design 197 9.6 Estimation of Missing Rainfall 202 9.7 Mean Depth of Rainfall Over an Area 203 9.8 Consistency of Rainfall Records 207 9.9 Extension and Interpretation of Rainfall Data 210 9.10 Intensity-Duration Relationships 212 9.11 Point Rainfall to Areal Rainfall Relationship 216 References 218 10. Design Storm Estimation 219 10.1 Rainstorm and its Analysis 220 10.2 Depth-area-duration Analysis of a Rainstorm 220 10.3 Design Storm 222 10.4 Data for Design Storm Studies 223 10.5 Methods for Estimating Design Storms 224 10.6 Probable Maximum Precipitation 229 10.7 Methods of Estimating PMP 230 References 242 11. Statistical Analysis of Precipitation 244 11.1 Data Series for Frequency Analysis 245 11.2 Recurrence Interval 246 11.3 Calculated Risk 247 11.4 Frequency Analysis 250 11.5 Measures of Central Tendency 255 11.6 Measures of Variability 256 11.7 Measures of Skewness 259 11.8 Measure of Kurtosis (Flattening) 261 11.9 Moments of Frequency Distribution 262 11.10 Standard Frequency Distributions 263 11.11 Homogeneity of Data 269 11.12 Empirical Frequency Analysis 270 11.13 Frequency Analysis by the Gumbel Method 274 11.14 Frequency Factors 276 References 277 12. Foreshadowing Precipitation 278 12.1 Correlation Analysis 278 12.2 Measure of Variability 282 12.3 Global Scale Factors Affecting Rainfall 285 12.4 Types of Weather Forecasts 289 12.5 Development of Long Range Forecast of Rainfall in India 290 12.6 Indian Summer Monsoon and Southern Oscillation Index 292 12.7 Statistical Techniques in Long Range Forecast based on Improved Parameters 293 Contents xv

12.8 Multiple Regression Analysis 294 12.9 Required Parameters in Long-range Forecasting of Indian Summer Monsoon Rainfall 297 References 298 13. Evaporation 300 13.1 Physics of Evaporation 300 13.2 Factors Affecting Evaporation 301 13.3 Measurement of Evaporation 303 13.4 Evaporation Measurement in India 304 13.5 Estimation of Evaporation by Indirect Methods 305 References 318 14. Droughts 319 14.1 Causes of Droughts 319 14.2 Evapotranspiration and Potential Evapotranspiration 321 14.3 Types of Droughts 323 14.4 Droughts in India 330 14.5 El Nino Factor Relating to Droughts 335 14.6 Absence of Tropical Disturbances and Indian Rainfall 337 References 340 15. Floods 342 15.1 Definition of Flood 343 15.2 Kinds of Floods 343 15.3 Causes of Floods 345 15.4 Effects of Floods 345 15.5 Surface Runoff and Runoff Process 347 15.6 Runoff Measurements 347 15.7 Hydrograph 348 15.8 Flood Control 349 15.9 Estimation of Peak Flood 352 15.10 Floods in Indian Rivers 369 15.11 Highest Floods in India 371 15.12 Comparison of the Highest Floods in India with World’s Highest Floods 373 References 375

Appendix: World Weather Extremes 377 Index 379