Crop Yield Estimation Using Remote Sensing and Surface Energy Flux Model

Abstract

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.Adrying 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 holdmoisture, 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.