Aerosols Measurements Made by Earth Observation Satellites

CEOS EO HANDBOOK – MEASUREMENTS

Measurements > Atmosphere >
Aerosols

Aerosols are tiny particles suspended in the air, with the majority derived from natural phenomena such as volcanic eruptions, thought it is estimated that some 10–20% are generated by human activities such as burning of fossil fuels. The majority of aerosols form a thin haze in the lower atmosphere and are regularly washed out by precipitation, with the remainder found in the stratosphere where they can remain for many months or years.

Detailed Measurement	Description*	Instruments	Timeline
Aerosol absorption optical depth (column/profile)	Optical depth (OD) is the integral of extinction in the vertical dimension (integral of extinction (km-1) dz). The transmittance of the atmosphere = T = Exp(-OD) = Exp(-Integral(extinction dz)).	16 instruments
Aerosol effective radius (column/profile)	Vertical profile of the size distribution of aerosol, assimilated to spheres of the same volume. Requested in the troposphere (assumed height: 12 km) and as columnar average - Physical unit: [ mm ] - Accuracy unit: [ mm ].	14 instruments
Aerosol Extinction / Backscatter (column/profile) Link:	3D field of spectral volumetric extinction cross-section of aerosol particles - Measuring Units m-1, Uncertainty Units m-1	21 instruments
Aerosol Layer Height Link:	Height of vertically localized aerosol layers in the free troposphere, such as desert dust, biomass burning aerosol or volcanic ash plumes. Measuring Units km, Uncertainty Units km	6 instruments
Aerosol optical depth (column/profile) Link:	The aerosol optical depth or optical thickness (τ) is defined as the integrated extinction coefficient over a vertical column of unit cross section.	35 instruments
Aerosol Single Scattering Albedo Link:	The spectrally dependent ratio of the aerosol scattering to the aerosol extinction.	3 instruments
Aerosol UV absorbing index	The Aerosol UV absorbing index is a scalar quantity evaluated from a pair of measured reflectances in the UV spectral domain. High values of the index indicate the presence of elevated absorbing aerosols (e.g. desert dust and biomass burning aerosols) in the Earth’s atmosphere. Physical unit: none. Accuracy unit: none	1 instrument
Visibility	The aerosol optical depth or optical thickness (τ) is defined as the integrated extinction coefficient over a vertical column of unit cross section.	1 instrument
Volcanic ash	The location of a volcanic ash cloud. [Unit of measurement – Lat/Long]	17 instruments

* Description adapted from WMO.