RAINFALL
Modeling, Measurement and Applications
Edited by Renato Morbidelli
Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
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2.4
2.4.1
CHAPTER 4
5.5 Errors in radar rainfall estimation and their correction...............
5.5.1 Variability of the Z-R relationship ....................................
5.5.2 Ground clutter ...................................................................
5.5.3 Beam blocking
5.5.4 Range-related errors and the vertical profile of radar reflectivity
5.5.5 Attenuation by intervening precipitation and due to a wet radome
5.5.6 Electrical stability of radar system ...................................
5.6 Radar – raingauge merging and assessment of radar rainfall uncertainty ..................................................................................
5.7 Dual polarization
5.8 Conclusions.................................................................................
6.1
6.2
6.2.1
6.2.2
6.3 Precipitation
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.4
6.5 Case study: hurricane Laura observed by the GPM Core Observatory .................................................................................
6.6
6.7
CHAPTER 7 Time resolution of rain gauge data and its
Renato Morbidelli, Corrado Corradini, Carla Saltalippi, Alessia Flammini
7.1
7.2
7.3 Rainfall data time-resolution in different geographic areas of the world ................................................................................. 173
7.4 Effect of data time-resolution on the estimate of annual maximum rainfall depths 181
7.4.1 Hyetograph shape and Hd underestimation ...................... 182
7.4.2 Development of average error relationships and correction of Hd series ...................................................... 186
7.5 Rainfall data time-resolution and its role in the hydrological applications ................................................................................. 188
7.6 Case study: Umbria region in central Italy 189
7.6.1 The history of the rainfall data time-resolution in the study area 189
7.6.2 The underestimation error of the annual maximum rainfall depth in the study region 193
7.6.3 Influence of ta on hydrological analyses in the study area 198
Ramesh S.V. Teegavarapu 8.1
8.3.6
8.3.7
8.3.8
8.4.5
8.4.6 Spline interpolation methods ......................................... 239
8.4.7 Surface fitting methods: issues....................................... 241
8.5 Radar and satellite-based methods ........................................... 242
8.6 Computationally intensive estimation methods ....................... 244
8.7 Mean areal precipitation estimation: issues ............................. 246
8.7.1 Precipitation monitoring network adequacy .................. 246
8.7.2 Quality of precipitation measurements .......................... 247
8.7.3 Missing precipitation data at rain gauges....................... 247
8.7.4 Quality of radar and satellite-based precipitation estimates ......................................................................... 249
8.7.5 Spatial interpolation approaches 250
8.8 Evaluation of mean areal precipitation estimation methods .... 250
8.9 Recommendations for selection of a mean areal precipitation estimation method ............................................... 252
8.10 Conclusions 254 References .......................................................................................... 254
CHAPTER 9
Ombrian curves advanced to stochastic modeling of rainfall intensity ............................... 261
Demetris Koutsoyiannis, Theano Iliopoulou
9.1 Introduction................................................................................. 261
9.2 A stochastic framework for building ombrian models 263
9.2.1 Basic requirements for an ombrian model ........................ 263
9.2.2 Characterization of second-order properties through climacogram ..................................................................... 264
9.2.3 Assigning empirical return periods using order statistics 266
9.3 Building a theoretically consistent ombrian model .................... 268
9.3.1 All-scale version 268
9.3.2 Simplified model for small scales ..................................... 272
9.4 Model fitting procedure 273
9.4.1 All-scale version ............................................................... 273
9.4.2 Simplified version 274
9.5 Development of an ombrian model for Bologna in Italy ............ 275
9.6 Discussion and further aspects 277
9.6.1 On the use of all data ........................................................ 279
9.6.2 On the estimation of the tail-index 280
9.6.3 On the use of a Hershfield coefficient............................... 280
9.6.4 Area-reduction of point ombrian curves 281
9.7 Conclusions.................................................................................
Alessia Flammini, Jacopo Dari, Corrado Corradini, Carla Saltalippi, Renato Morbidelli
Hayley J. Fowler, Haider Ali
CHAPTER 12 Rainfall regionalization techniques ..................... 327
Pierluigi Claps, Daniele Ganora, Paola Mazzoglio
12.1 Introduction ..............................................................................
12.2 Variables to be regionalized, data preparation, and data scarcity .....................................................................................
12.2.1 Regionalized variables..................................................
12.2.2 Data preparation and data scarcity ...............................
12.3 Regional methods .....................................................................
12.3.1 Fixed region and region-of-influence methods
12.3.2 Regionless methods ......................................................
12.3.3 Geostatistical techniques
12.4 Methods adopted in practice ....................................................
12.4.1 National atlases
12.5 Considerations on applicability and evolution of the regional frequency analyses
12.6 Conclusions ..............................................................................
CHAPTER 13 Rainfall and development of floods ...................... 351
Carla Saltalippi, Corrado Corradini, Jacopo Dari, Renato Morbidelli, Alessia Flammini
13.1 Introduction
13.2 Formation and separation of the flood hydrograph .................. 352
13.3 A modeling framework for flood simulation and real-time flood forecasting.......................................................................
13.4 A short description of the implicit functions incorporated in the real-time flood forecasting model framework .................... 358
13.5 Rainfall-runoff for designing extreme floods
Conclusions ..............................................................................
CHAPTER 14 Rainfall and infiltration
Rao S. Govindaraju, Abhishek Goyal
14.1 Introduction ..............................................................................
14.2 Rainfall-infiltration process
14.3 Point infiltration methods .........................................................
14.3.1 Empirical equations
14.3.2 Green-Ampt model .......................................................
14.3.3 Philip model
14.3.4 Parlange-Lisle-Braddock-Smith model ........................
CHAPTER 15 Rainfall and erosion/sediment transport
CHAPTER 16
16.3 The TRIGRS physically-based model .....................................
16.4 Rainfall thresholds for landslide initiation ............................... 432
16.4.1 Frequentist method for the definition of rainfall thresholds 434
16.4.2 Validation of rainfall thresholds ................................... 437
16.5 Operational prediction and forecasting of rainfall-induced landslides.................................................................................. 439
16.6 Case study: frequentist thresholds for landslide initiation in Italy ...................................................................................... 441
16.7 Conclusions
CHAPTER 17 Rainfall
Ashok Mishra, Ali Alnahit, Sourav Mukherjee
17.1 Introduction .............................................................................. 451 17.2 Drought hydrology and generating processes .......................... 453
17.3 Drought indices 455
17.3.1 Standardized precipitation index (SPI)......................... 456
17.3.2 Standardized precipitation-evapotranspiration index (SPEI) ................................................................. 458
17.3.3 Palmer drought severity index (PDSI) 459
17.4 Case study: drought characterization using SPI, SPEI, and PDSI 460
17.4.1 Background .................................................................. 460
17.4.2 Temporal evolution and characteristics of drought 462
Conclusion ............................................................................... 466
Contributors
Haider Ali
School of Engineering, Newcastle University, United Kingdom
Ali Alnahit
Department of Civil Engineering, King Saud University, Riyadh, Saudi Arabia
Marco Borga
Department of Land Environment Agriculture and Forestry, University of Padova, Padova, Italy
Maria Teresa Brunetti
CNR IRPI - Italian National Research Council, Research Institute for the GeoHydrological Protection, Perugia, Italy
O. Castro-Orgaz
University of Córdoba, Department of Agronomy, Córdoba, Spain
Arianna Cauteruccio
University of Genova, Dept. of Civil, Chemical and Environmental Engineering, Genoa, Italy; WMO/CIMO Lead Centre “B. Castelli” on Precipitation Intensity, Italy
Pierluigi Claps
Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, Torino, Italy
Corrado Corradini
Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
Jacopo Dari
National Research Council, Research Institute for Geo-Hydrological Protection, Perugia, Italy; Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
Alessia Flammini
Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
Hayley J. Fowler
School of Engineering, Newcastle University, United Kingdom
Marco Gabella
Meteoswiss, Locarno Monti, Switzerland
Daniele Ganora
Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, Torino, Italy
Stefano Luigi Gariano
CNR IRPI - Italian National Research Council, Research Institute for the GeoHydrological Protection, Perugia, Italy
Contributors
J.V. Giráldez
University of Córdoba, Department of Agronomy, Córdoba, Spain; Institute for Sustainable Agriculture, CSIC, Department of Agronomy, Córdoba, Spain
Rao S. Govindaraju
Lyles School of Civil Engineering, Purdue University, West Lafayette, IN, United States
Abhishek Goyal
Lyles School of Civil Engineering, Purdue University, West Lafayette, IN, United States
Wojciech W. Grabowski
Mesoscale and Microscale Meteorology Laboratory, NCAR, Boulder, CO, United States
Fausto Guzzetti
Civil Protection Department, Office of the Prime Minister, Rome, Italy
J.A. Gómez
Institute for Sustainable Agriculture, CSIC, Department of Agronomy, Córdoba, Spain
Theano Iliopoulou
Department of Water Resources and Environmental Engineering, National Technical University of Athens, Zographou, Greece
Christopher Kidd
Earth System Science
Interdisciplinary Center, University of Maryland, MD, United States; NASA Goddard Space Flight Center, Greenbelt, MD, United States
Demetris Koutsoyiannis
Department of Water Resources and Environmental Engineering, National Technical University of Athens, Zographou, Greece
A.M. Laguna
University of Córdoba, Department of Applied Physics, Córdoba, Spain
Luca G. Lanza
University of Genova, Dept. of Civil, Chemical and Environmental Engineering, Genoa, Italy; WMO/CIMO Lead Centre “B. Castelli” on Precipitation Intensity, Italy
Vincenzo Levizzani
Institute of Atmospheric Sciences and Climate, National Research Council (CNR-ISAC), Bologna, Italy
Francesco Marra
Institute of Atmospheric Sciences and Climate, National Research Council (CNR-ISAC), Bologna, Italy
Paola Mazzoglio
Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, Torino, Italy
Greg M. McFarquhar
Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK, United States
Massimo Melillo
CNR IRPI - Italian National Research Council, Research Institute for the GeoHydrological Protection, Perugia, Italy
Ashok Mishra
Glenn Department of Civil Engineering, Clemson University, South Carolina, United States
Renato Morbidelli
Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
Sourav Mukherjee
Glenn Department of Civil Engineering, Clemson University, South Carolina, United States
Silvia Peruccacci
CNR IRPI - Italian National Research Council, Research Institute for the GeoHydrological Protection, Perugia, Italy
Carla Saltalippi
Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
Mattia Stagnaro
University of Genova, Dept. of Civil, Chemical and Environmental Engineering, Genoa, Italy; WMO/CIMO Lead Centre “B. Castelli” on Precipitation Intensity, Italy
Ramesh S.V. Teegavarapu
Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton, Florida, United States
Preface
Even though different types of precipitation can occur, this book is substantially related to rainfall formed from condensation or sublimation of water vapor over condensation nuclei with successive coagulation and precipitation at the ground surface. Rainfall, characterized by a droplet size distribution, is a major component of the water cycle and gives a crucial contribution to the fresh water on the Earth. It produces suitable conditions for many types of ecosystems and is useful for hydroelectric power plants and crop irrigation.
This book integrates different rainfall perspectives from microphysics and modeling developments to experimental measurements and their analysis also in the context of applications in surface and subsurface hydrology. It is mainly directed to postgraduate readers studying meteorology, civil and environmental engineering, geophysics, agronomy and natural science, as well as practitioners working in the fields of hydrology, hydrogeology, agronomy, and water resources management. Each chapter provides an updated representation of the involved subject with relative open problems.
Chapter 1 describes elements of microphysics inside and beneath clouds producing rainfall at Earth’s surface, highlighting discoveries of the last 100 years that have led to significant improvement of our knowledge. The chapter describes processes associated to both warm and cold rain.
In Chapter 2, the production of precipitation through the development of vertical motions in the atmosphere is considered. The lifting of humid air mass due to frontal disturbances, orographic chains, convective systems, and humid air convergence is discussed. In this context, the spatio-temporal distribution of rainfall is widely analyzed for frontal systems influenced by the interaction of the above lifting mechanisms.
Chapter 3 discusses the progress in the last decades regarding two fundamental elements for rainfall modeling: formulation of moist air dynamics and representation of formation and fallout of precipitation.
Chapter 4 describes and discusses the catching and noncatching instruments of rainfall measurements (raingauges) and their main characteristics. Standard calibration methods are reported for catching-type gauges. Optimal correction algorithms for the interpretation of tipping-bucket raingauge records are presented, together with correction methods for both tipping-bucket and weighing gauges. The impact of wind on rainfall measurements is discussed on the basis of the outer shape of the gauge body, and suitable correction curves are reported for cylindrical gauges. The relevance of measurement accuracy and quality in rainfall monitoring is highlighted and a brief section on the design of monitoring networks is included.
Chapter 5 provides an outline of the principles of precipitation estimation by means of weather radar, with coverage of the main measurement techniques and methods used to generate rainfall products starting from weather radar observations.
Chapter 6 points out that the use of conventional instruments (gauge or radar) to map global precipitation is essentially limited to land areas and thus satellite observations must be used to provide estimates of global precipitation. Many satellite sensors operating in the last 50 years provided data for a range of techniques, algorithms, and schemes developed to obtain quantitative precipitation estimates. Spacetime limitations of current satellite-based precipitation products are described. This chapter outlines the basis of satellite precipitation estimation, satellites and sensors types, and techniques and schemes used to generate the precipitation products.
In Chapter 7, the role of a limited and not homogeneous temporal resolution of rain gauge data in the analysis of commonly available historical series is discussed to provide evidence of possible errors in hydrological investigations. Particular emphasis is given to the effects on the analysis of extreme rainfalls that have a crucial role in designing hydraulic structures. Simple equations to improve the determination of extreme values are also provided.
Mean areal rainfall estimate using deterministic and stochastic methods is presented in Chapter 8. Conceptually weighting methods that use raingauge-based observations and gridded rainfall data from radar and satellite-based sources are described.
Chapter 9 presents the typical form of mathematical relationships linking maximum rainfall intensity of different durations to the return period, also known as intensity-duration-frequency curves, along with its merits and limitations. A modeling framework to overcome the limitations is also described. Two variants of the model are presented: a full version valid over time scales and a simplified relationship applicable over fine scales of the order of common applications, i.e., sub-hourly to daily.
In Chapter 10, the main factors influencing the rainfall areal reduction factors (ARFs) are described. The main empirical and analytical approaches available in the scientific literature to estimate ARFs are presented and critically discussed. The crucial issue of the transposition and applicability of ARFs developed for a certain area to other regions is also deepened by presenting the results of several studies.
In Chapter 11, recent advances in studying the extreme rainfall through recorded quantities available from measurements on a sub-daily/multi-day time scale are described. Future changes of rainfall extremes are discussed on the basis of climate model outputs. This is achieved by examining different available models and understanding the relationships between rainfall extremes and temperature.
Chapter 12 summarizes the state of the art of regionalization techniques applied to rainfall data. First, current problems in data availability are identified. Then, differences between traditional and more innovative approaches aimed to provide intensity-duration-frequency curves everywhere in a large area are highlighted. Furthermore, this chapter explores the advantages of interpolation methods over the homogeneous region paradigm, addressing in particular the objective of valorization of the local information deriving from short records.
Chapter 13 first deals with the formation and separation of the flood hydrograph through the effective hyetograph associated to a specific rainfall-runoff event. On this basis the main structure of typical rainfall-runoff models for simulating single
flood events is highlighted in general terms. Then, the specific structure of an adaptive rainfall-runoff model for real-time flood forecasting is also examined. Finally, through a synthetic statistical analysis of extreme rainfalls, a classical procedure for determining the design hydrograph of hydraulic structures is presented.
In Chapter 14, the rainfall pattern role in determining the infiltration process is examined. In this context, a quantitative representation of the rainfall infiltration process at different spatial scales is provided considering also erratic spatio-temporal rainfall distributions. Artificial rainfall systems useful for determining the main soil properties are also synthetically presented.
In Chapter 15, the exploration of the main features of soil erosion controlled by rainfall has been carried out; starting from this analysis some relevant aspects that might deserve more attention by the research in the near future can be detected.
In Chapter 16, a grid-based slope stability model for the spatial and temporal prediction of rainfall-induced landslides is described after a general characterization of physically-based and empirical approaches. A particular emphasis has been placed on a widely used empirical method for the prediction of landslide initiation, i.e., rainfall threshold.
Chapter 17 highlights the importance of rainfall in drought assessment. An overview of the role of rainfall in drought evaluation is provided and the most common precipitation-based drought indices are pointed out. The various challenges and limitations associated with quantifying the evolution of drought using the rainfall-based drought indices are emphasized.
