Evaporation and Evapotranspiration

Transcription

1 Evaporation and Evapotranspiration

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3 Wossenu Abtew Assefa Melesse Evaporation and Evapotranspiration Measurements and Estimations 123

4 Dr. Wossenu Abtew South Florida Water Management District West Palm Beach, FL USA Prof. Dr. Assefa Melesse Department of Earth and Environment Florida International University Miami, FL USA ISBN ISBN (ebook) DOI / Springer Dordrecht Heidelberg New York London Library of Congress Control Number: Springer Science+Business Media Dordrecht 2013 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher s location, in its current version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the Copyright Clearance Center. Violations are liable to prosecution under the respective Copyright Law. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Printed on acid-free paper Springer is part of Springer Science+Business Media (

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7 Preface Water loss through evaporation from open water and evapotranspiration (ET) from vegetation is one of the major components of the hydrologic cycle affecting water resources availability. Measurement and estimation of these terms have initiated the development of the theory of the process, measurement techniques, and estimation equations. Perceptions have contributed to biases of estimation. A drying pond taken over by vegetation gives the perception that the vegetation s increased ET resulted in the drying of the pond. Succession of vegetation in a wetland may hide the impact of changing hydrology by suggesting water losses are due to invading vegetation. The evapotranspiration process is controlled by the availability of moisture to evaporate. Energy is required to detach water molecules. A mechanism is required to move the vapor into the air column. The air has to have the capacity to hold the vapor. When the air has no more capacity to hold moisture, the reverse process, dew formation, occurs. In this book, dew evaporation is presented in a chapter. A chapter on vapor pressure and vapor pressure deficit estimation methods is presented with known quality data from a monitoring network. ET processes and mechanisms are presented in a simplified way without compromising complexity. In each case, examples of applications from the authors experience are presented for comparing estimation methods. Meteorological monitoring and data quality, input into ET estimation methods, is vastly discussed in a chapter with illustrations from a large monitoring network. The design and application of a lysimeter system for open water evaporation and wetland vegetation ET has provided measured data to gauge the performance of various estimation equations. The advantage and limitation of simple ET estimation methods, when input data is limited, are addressed. Remote sensing application to ET estimation is sufficiently addressed in three chapters with application case studies. An introduction into the expected impact of climate change on ET rates is included as a chapter with climate model application results. This book is a useful resource for hydrologists, scientists, meteorologists, engineers, water resource managers, agricultural and environmental professionals, students, and teachers. Wossenu Abtew vii

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9 Contents 1 Introduction Overview of Evaporation and Evapotranspiration Studies... 1 References Meteorological Parameter Monitoring and Data Quality Introduction Meteorological Parameters Monitoring Network Sources of Error in Meteorological Parameters Air Temperature Dew Point Temperature Humidity Water Temperature Atmospheric Pressure Wind Speed and Wind Direction Wind Profile Wind Barrier s Impact on Wind Speed and Pattern Solar Radiation Net Solar Radiation Summary References Evaporation and Evapotranspiration Measurement Introduction Pan Evaporation Lysimeters Weighing Lysimeter Water Balance Lysimeter Eddy Correlation Bowen Ratio Lidar (Light Detection and Ranging Method) Satellite-Based Methods ix

10 x Contents 3.8 Summary References Energy Requirements of Dew Evaporation Introduction Energy Balance and Transfer Coefficients Dewfalls and Evaporation Summary References Vapor Pressure Calculation Methods Introduction Comparison of Vapor Pressure Computation Methods Methods Results Summary References Evaporation and Evapotranspiration Estimation Methods Introduction Simple Methods Pan Method Temperature-Based Methods Radiation-Based Methods Solar Radiation Maximum Temperature Method Mass Transfer Method Complex Methods Energy Balance Methods The Penman Method Remote Sensing Methods Summary References Wetland Evapotranspiration Introduction Wetland Evapotranspiration Measurement and Modeling Lysimeters Wetland ET Modeling from Lysimeter Observations Bowen Ratio Energy Balance Method Penman Monteith Method Summary References Lake Evaporation Introduction Lake Evaporation Estimation Methods Pan Method

11 Contents xi Water Balance Method Energy Balance Mass Transfer Method The Penman Method The Simple Abtew Method Solar Radiation Maximum Temperature Method Modified Turc Equation Priestley Taylor Method Energy Balance Bowen Ratio Method (EBBR) Summary References Reference and Crop Evapotranspiration Introduction Reference Evapotranspiration Crop Canopy Resistance (r c ) Aerodynamic Resistance (r a ) The ASCE Standardized Reference Evapotranspiration Equation Potential Evapotranspiration and Evaporation Potential Evapotranspiration from Pan Evaporation Crop Coefficients Summary References Spatially Distributed Surface Energy Flux Modeling Introduction Remotely Sensed Data Landsat ASTER MODIS Surface Energy Budget and Models Surface Energy Balance Algorithm for Land (SEBAL) Two-Source Energy Balance (TSEB) Model Surface Energy Balance System (SEBS) Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC) Simplified Surface Energy Balance (SSEB) Simplified Surface Energy Balance Index (S-SEBI) Summary References Crop Yield Estimation Using Remote Sensing and Surface Energy Flux Model Introduction Surface Energy Flux Budget

12 xii Contents 11.3 Case Study Data Results and Discussion Summary References Wetland Restoration Assessment Using Remote Sensingand Surface Energy Budget-Based Evapotranspiration Introduction Case Studies Glacial Ridge Prairie Restoration Kissimmee River Restoration Methodology Satellite Image Preprocessing Evapotranspiration Mapping Results and Discussion Glacial Ridge Kissimmee River Basin Summary Glacial Ridge Kissimmee River Basin References Climate Change and Evapotranspiration Introduction Climate Change and Evapotranspiration Summary References Index

13 Symbols and Abbreviations A Area a, b Coefficients AET Actual ET a w, b w Coefficients c Adjustment factor c 1, c 2, c 3, c 4 Coefficients C et Reference crop coefficient C n, C d Coefficients c p, C p Specific heat of air, heat capacity of air c s Soil or water heat capacity d Displacement height d TM Constant ( mwcm2sr -1 m -1 ) de Change in vapor pressure d e-s Relative distance between Earth and Sun in astronomical units DN Digital number d r Inverse squared relative distance between Earth and Sun d s Effective depth dt Change in temperature between two measurement heights T Change in temperature dt Change in time du Change in wind speed d w Water depth dz Change in wind speed measurement height e Errors E, LE Vapor flux, latent heat flux, evaporation e d Actual vapor pressure e dd Vapor pressure in the air above evaporating surface elev Elevation above sea level E L Lake evaporation E o Open water evaporation Saturation vapor pressure at lake surface e o xiii

14 xiv Symbols and Abbreviations E p Potential evaporation E pan Pan evaporation e s, e a Saturation vapor pressure e ss Vapor pressure at evaporating surface ESUN The mean solar exoatmospheric irradiance ET Evapotranspiration ET 24 Daily ET from remotely sensed instantaneous ET ET aero Aerodynamic component ET ET c Actual crop evapotranspiration ET frac ET fraction for each pixel (average of hot and cold pixels) ET i Remotely sensed instantaneous ET ET o Evapotranspiration from grass reference crop (8 to 15 cm and well watered) E p Potential evaporation ET p Potential evapotranspiration ET r Reference crop evapotranspiration; grass reference ET ET rad Radiation component ET ET ref Reference ET ET r F Alfalfa reference evapotranspiration fraction ET sz Standardized reference crop evapotranspiration for short or tall crop f Fractional vegetation cover f (u) Function of the horizontal wind F c Fraction of cover f c Fractional canopy cover G Heat storage GAIN Solar spectral radiance for each band g b Boundary layer conductance g c Canopy conductance g m Measured conductance of leaf g s Stomatal conductance in mmol m -2 s -1 G sc Solar constant g sv Stomatal conductance in mm s -1 H Sensible heat h Reference vegetation height h c Average height of cover or crop height H s Sensible heat for soil surface H v Sensible heat for vegetation surface I Inflow J Julian day k Von Karman constant K 1, K 2, K 3 Coefficients K 1ls, K 2ls Calibration constants for Landsat 5 and 7 K c Crop coefficient k h Coefficient for sensible heat transfer Mass transfer limiting term k m

15 Symbols and Abbreviations xv K p K t k w pan coefficient Transfer coefficient Coefficient for latent heat transfer L Obukhov length LAI Leaf area index LE s Latent heat for soil surface LE v Latent heat for vegetation surface L j Leaf area index for canopy strata j L max Maximum spectral radiance L min Minimum spectral radiance m Constant ( mwcm 2 sr 1 m 1 ) MSE Mean square error n/n Mean actual to possible sunshine ratio NDVI Normalized Difference Vegetation Index NDVs Scaled NDVI NIR Near infrared band N o Mass transfer coefficient NTC Negative temperature coefficient O Outflow P Atmospheric pressure p Mean daily percentage total annual daytime hours PRT Platinum resistance thermometer PTC Positive temperature coefficient q Specific humidity q 0 Specific humidity fluctuation Q a Advective energy gain or loss Q h Sensible heat gain or loss Q in Energy input into the system Q out Energy leaving the system Q Rn Energy from net solar radiation r Correlation coefficient R Linear function of the digital number (DN) R A Extraterrestrial solar radiation r a Aerodynamic resistance R b, R L Net back or outgoing thermal radiation r c Canopy resistance RED Red band R f Rainfall RH Relative humidity RH avg24 Average humidity from 24-h continuous observations RH max Daily maximum relative humidity RH min Daily minimum relative humidity r l Stomatal resistance of a single leaf R n, R Sn Net solar radiation

16 xvi Symbols and Abbreviations R n,s Net solar radiation on soil surface R n,v Net solar radiation on vegetation surface R s Incoming solar radiation r s Stomatal resistance R s Resistance to heat flow in the boundary layer immediately above the soil surface R so Clear sky solar radiation R x Ground reflectance for band x S Slope S cj Stomatal conductance of leaf strata j Sp Seepage Std Standard deviation S y/x Standard error T A given temperature T a Air temperature over a lake, near surface air temperature T avg Average air temperature T avg24 Average temperature from 24-h continuous observations T d Dew point temperature T max Daily maximum air temperature T min Daily minimum air temperature T n Average temperature on day n T n 1 Average temperature on previous day T s Lake surface water temperature T sur Radiometric surface temperature T v Vegetation surface temperature u* Friction velocity or shear velocity u day Daytime wind speed u z Wind speed at height z vpd, e Vapor pressure deficit w Vertical wind speed w 0 Vertical wind speed fluctuation WI Wetness index z h Roughness length for heat transfer z o /z om Aerodynamic roughness/ roughness height or length for momentum transfer z oh Roughness length for vapor and heat transfer Albedo path-radiance Path radiance albedo toa Albedo of the top of atmosphere ˇ Bowen ratio Psychrometric constant ı Change in depth Slope of vapor pressure curve e Change in vapor pressure Q s Change in energy storage

17 Symbols and Abbreviations xvii S Change in storage SM Change in soil moisture T Change in temperature with time " Ratio of molecular weight of water to dry air " a Atmospheric emissivity " s Surface emissivity short Absorptivity * Temperature scale,s Solar declination angle in radians a Potential air temperature at height z o Potential temperature at the surface o a Mean surface temperature v Potential virtual temperature near the surface Latent heat of vaporization of water r Relative evaporative fraction s Thermal conductivity of soil Air density c Coefficient v Coefficient Stefan Boltzmann constant Shear stress o Surface shear stress sw One-way atmospheric transitivity ' Latitude in radians h Stability correction factor/function for sensible heat transfer m Stability correction factor/function for momentum transfer

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