Energy Balance principles are critical to understanding how radiation from the sun causes evaporation of water from: the ocean, the ground, and crop plants. Our crops are in the hot sun all day and use a lot of water to stay cool. There is no easy way to measure the amount of water they need, but we can calculate it using energy balance principles.
In this sevenlecture series, Dr. Bruce Bugbee, a Professor of Crop Physiology at Utah State University, explains the principles of energy balance in environmental systems. These principles, based on the first law of thermodynamics, are a corner stone in the larger discipline of Environmental Biophysics.
Lecture Series Introduction
Lecture 1 


Outline
 Introduction: The magnitude of water use in agriculture
 The challenge of measuring water use and evapotranspiration
 Reference books on environmental physics
 First law of thermodynamics: energy in equals energy out
 The seven components of the energy balance equation
 The magnitude of latent heat of evaporation
 Understanding energy and power
 Shortwave and longwave radiation
 E = mc^{2} homework
Lecture 1 Handouts

Lecture 2 


Outline
 Key for homework: units conversion Calories v. calories
 Calculating the efficiency of photosynthesis
 Calculating absorbed shortwave radiation – importance of albedo
 The three components of shortwave radiation
 Definitions of shortwave and longwave radiation
 The StefanBoltzman Law for longwave radiation
Lecture 2 Handouts

Lecture 3 


Outline
 The concept of emissivity
 Calculating long wave emitted
 Calculating net long wave radiation
 Calculating net absorbed short and longwave radiation
Lecture 3 Handouts

Lecture 4 


Outline
 Understanding the radiation balance on Earth
 Differential absorption of shortwave radiation
 Reflectance of longwave radiation
 Wein's Law
 Planck's Equation
Lecture 4 Handouts

Lecture 5 


Outline
 Transpiration
 Absolute and relative humidity
 flux = driving gradient x conductance
 Calculating the driving gradient
 Determining stomatal conductance
 Modelling transpiration
Lecture 5 Handouts

Lecture 6 


Outline
 Conduction and convection
 Calculating boundary layer conductance
 Measurement of the driving gradient
 Modelling convective heat transfer
Lecture 6 Handouts

Lecture 7 


Outline
 Energy balance principles at night: Radiation frost
 Energy balance principles in the PenmanMonteith equation
 The Simplicity of Hagraves equation
Lecture 7 Handouts

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