Lecture 15 Flashcards
What emits Thermal IR energy
Rocks, soil, vegetation and animals emit thermal IR energy
How can energy be transferred between objects
Conduction - occurs when one body (molecule or atom) transfers its kinetic energy to another by colliding with it.
- this is how a pan is heated on a stove.
Convection - kinetic energy of bodies is transferred from one place to another by physically moving the bodies - an example is convectional heating of air in the atmosphere in the early afternoon.
why is transfer of energy by EM radiation a key interest
it is the form of energy transfer that we can sense remotely
What is absorption in the thermal IR due to
atmospheric water vapour / co2 and o3
where is thermal IR absorption minimal?
~3-5μm & ~8-14 μm
how long is thermal IR in comparison to visible and NIR
longer wavelength
What are the 3 key laws that describe thermal properties of objects
- Planck’s Law
* Describes the distribution of energy with wavelength as a function of Temperature - Stefan-Boltzman Law
* Describes the relationship between the total energy emitted and temperature - Weins displacement Law
* Describes the spectral distribution of energy as a function of temperature
What is Planck’s Law
Describes the distribution of energy (shape of curve on graph) with wavelength as a function of Temperature
Energy distribution with wavelength depends on Temperature
Characteristic steep rise @ short wavelengths
Characteristic long tail @ long wavelengths
Stefan-Boltzman Law
Describes the relationship between the total energy emitted (area under the curve) and temperature
The amount of energy than an object radiates
▪ It is important to note that the total energy emitted from an object varies with T4 (temp to temp power of 4)
▪ increases rapidly with increases in temperature
Weins displacement Law
Describes the spectral distribution of energy as a
function of temperature
Just as total energy varies with temperature, the spectral distribution of energy varies also.
▪ The dominant wavelength at which a blackbody radiation curve reached
- a maximum, is related to temperature by Weins Law
peak of curve moves further to the left as the object increases
Which satelite sensors have a TIR (whats a TIR)
TIR = thermal infrared waveband (8-14 micro metres)
- Landsat TM/ETM
Moderate Resolution Imaging Spectroradiometer (MODIS)
* Advanced Spaceborne Thermal Emission and Reflection
Radiometer (ASTER)
* Sea and Land Surface Temperature Radiometer (SLSTR)
* Spinning Enhanced Visible and Infrared Imager (SEVIRI)
* Geostationary Operational Environmental Satellite (GOES)
Which satellites have MIR waveband?
MIR = middle infrared waveband 3-5 micro metres
Moderate Resolution Imaging Spectroradiometer (MODIS)
* Sea and Land Surface Temperature Radiometer (SLSTR)
* Spinning Enhanced Visible and Infrared Imager (SEVIRI)
* Geostationary Operational Environmental Satellite (GOES)
What is an urban heat island?
Urban areas are warmer, like an “island” of heat surrounded by cooler rural areas
▪ UHI characterized by higher air and surface temperatures
Urban materials (concrete, asphalt, tarmac etc) absorb sunlight and then radiate heat
▪ Vegetation and water surfaces have a cooling effect
▪ transpiration and evaporation
▪ shade
What are the problems of urban heat islands?
Elevated urban temperatures have negative environmental and health impacts
▪ Increased energy demand
▪ air pollution (O3)
▪ heat-related illness and mortality
▪ Especially during heatwaves ▪ Predicated to increase with climate change
▪ Cool technologies : more reflective materials and green roofing, more green space
What does remote sensing have to do with volcano monitoring
Satellite remote sensing is an important early warning system for volcanic eruptions (lave and pyroclastic flows and ash clouds).
Crater lakes on volcanoes act like calorimeters, absorbing heat given off by intruding magma
Approximately 12% of the world’s 700 or so active volcanoes have crater lakes
