Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Emission Index The mass of material or number of particles emitted per burnt mass of fuel (for NO x in g of equivalent NO 2 per kg of fuel; for hydrocarbons in g of CH 4
per kg of fuel).
Energy Efficiency Ratio of energy output of a conversion process or of a system to its energy input; also known as first-law efficiency.
Engine Pressure Ratio The ratio of the mean total pressure at the last compressor discharge plane of the compressor to the mean total pressure at the compressor
entry plane, when the engine is developing its take-off thrust rating (in ISA sea-level static conditions).
Equivalence Ratio Ratio of actual fuel-air ratio to stoichiometric fuel-air ratio.
Feedback When one variable in a system triggers changes in a second variable that in turn ultimately affects the original; a positive feedback intensifies the effect, and
a negative reduces the effect.
Freezing The process of phase transition from liquid to solid state.
Freezing Nucleus Any particle that, when present within a mass of supercooled water, will initiate growth of an ice crystal about itself.
Greenhouse Gas A gas that absorbs radiation at specific wavelengths within the spectrum of radiation (infrared) emitted by the Earth's surface and by clouds. The gas
in turn emits infrared radiation from a level where the temperature is colder than the surface. The net effect is a local trapping of part of the absorbed energy and a
tendency to warm the planetary surface. Water vapor (H 2 O), carbon dioxide CO 2 ), nitrous oxide (N 2 O), methane (CH 4 ), and ozone (O 3 ) are the primary greenhouse
gases in the Earth's atmosphere.
Heterogeneous Chemistry Chemical reactions that involve both gaseous and liquid/solid ingredients.
Heterogeneous Nucleation Formation of liquid or solid particles on the surface of other material.
Homogeneous Chemistry Chemistry in the gas phase.
Homogeneous Nucleation Formation of particles from gas-phase species.
Indirect Radiative Impact Radiative forcing induced not directly but by changing other scattering or absorbing components of the atmosphere (clouds or gases).
Jet The continuous strong stream of exhaust gases leaving the engine exit.
Kerosene Hydrocarbon fuel for jet aircraft.
Landing/Take-Off (LTO) Cycle A reference cycle for the calculation and reporting of emissions, composed of four power settings and related operating times for
subsonic aircraft engines [Take-Off - 100% power, 0.7 minutes; Climb - 85%, 2.2 minutes; Approach - 30%, 4.0 minutes; Taxi/Ground Idle - 7%, 26.0 minutes].
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