Lec 12 - Introduction to Thermal Infrared Flashcards
Also known as longwave infrared (LWIR)
Thermal Infrared
It is the sensing of emissive energy or “temperature” energy
Thermal Infrared
Remote Sensing Measures (4)
(1) Land and Ocean Surface Temperature
(2) Atmospheric
(3) Radiation Balance
(4) Emissivity
It is the parameter indicating the energy and water exchange between the surface and the atmosphere.
Land and Ocean Surface Temperature
It measures temperature and amount of water vapor at different levels of the atmosphere
Temperature and humidity
Other gasses present in small amounts within the atmosphere.
Trace Gas Concentration
The balance between the radiant energy received by the Earth from the Sun and that returned by Earth to space
Radiation Balance
The ratio of the energy radiated from a material’s surface to that radiated from a perfect emitter (blackbody)
Emissivity
The measure of the motion of atoms and molecules in a substance
Temperature
Energy of particles of matter in random motion
Kinetic Heat
It can be measured using a thermometer
True Kinetic Temperature (Tkin)
The emitted EM radiation caused by the collision of particles with kinetic heat
Radiant Flux (Watts)
The amount of radiant flux emitted from an object
Radiant Temperature (Trad)
Relationship between Tkin and Trad
There is usually a high positive correlation between the true kinetic temperature of an object (Tkin) and the amount of radiant flux radiated from the object (Trad)
The most obvious source of EM radiation for remote sensing
Sun
The ratio of radiance spectrum of a non-perfect emitter over that of a perfect emitter (blackbody) at the same temperature.
Emissivity spectrum
The perfect absorber and emitter
Blackbody
The law states that, “The total energy emitted/radiated per unit surface area of a blackbody across all wavelengths per unit time is directly proportional to the fourth power of the black body’s thermodynamic temperature.
Stefan-Boltzmann Law
This law states that black body radiation has different peaks of temperature at wavelengths that are inversely proportional to temperatures.
Wien’s Displacement Law
This means reflectivity and emissivity has an inverse relationship; “good absorbers are good emitters” and “good reflectors are poor emitters”
Kirchoff’s Radiation Law
The most commonly used method for land surface temperature (LST) retrieval from satellite data (Wang et. al, 2019)
Split-window algorithm
The measure of the increase in thermal energy content (Q) per degree of temperature rise
Thermal/heat capacity (C)
The rate at which heat will pass through a material
Thermal conductivity (K)
The rate at which temperature can change within a body (energy loss / gain characteristics)
Thermal diffusivity (k)
It is a measure of a substance’s ability to transfer heat in and out of that portion that received solar heating during the day and cools at night (cm^2/s)
Thermal diffusivity (k)
The thermal response, delay in reaching ambient temperature following exposure to energy
Thermal inertia (P)
The measure of the heat transfer rate across a boundary between two materials
Thermal inertia (P)
Any pattern that recurs every 24 hours as a result of one full rotation of the planet Earth around its axis.
Diurnal cycle (or diel cycle)
Thermal Properties of Water
(1) Cooler in the day and warmer in the night relative to other materials in the scene
(2) High thermal inertia, relative to typical land surfaces, as controlled largely by water’s high specific heat.
A device designed to measure and detect thermal (heat) energy.
Thermal energy detector
The basic principle is the conversion of heat into a measurable signal.
Thermal energy detector
This produces a voltage when heated
Thermocouple
It undergoes a change in electrical resistance when heated
Bolometer
It is much more complex and expensive and is not used on the best-selling thermal camera models for various applications
Quantum detector
It is sensitive to infrared radiation, which is a form of thermal energy.
Infrared (IR) Detectors
It is temperature-sensitive resistors whose resistance changes significantly with temperature
Thermistors
Common Satellite Sensors in Thermal IR
(1) Landsat 8
(2) NOAA AVHRR Band 4
(3) GOES, GMS, MOS 1, SeaWiFs, Nimbus CZCS (1 thermal), SeaSat, HCMM
(4) Ceres
Thermal Infrared (TIR) Applications
(1) provide accurate distributions of surface spectral emittance and temperature
(2) Heat and moisture fluxes (exchanges)
(3) Climatological processes
(4) Evapo-transpiration
(5) Soil moisture variation
(6) Hydrology, oceanography and ocean currents
(7) Biomass distribution
(8) Vegetation monitoring
(9) Lithology & geology
(10) Urban land use
(11) Natural disaster monitoring
(12) Thermal pollution
