atmosphere_optical_thickness_due_to_ambient_aerosol_particles_assuming_clear_sky

under discussion

Created: 12 Jun 2026

Proposer: Tommi Bergman

Proposed Date: 2025-05-21

CMIP7

Standard names: aerosol optical depths for clear sky, secondary organic and biomass burning aerosols (od550csaer, od550soa, od550bb)

Change Date: 12 Jun 2026, 12:52 p.m.

atmosphere_optical_thickness_due_to_ambient_aerosol_particles_assuming_clear_sky 1 [UUUU] P07 id: QW5TE9YE
AOD from aerosols assuming cloud free fraction of gridbox if od550aer is for all-sky. The optical thickness is the integral along the path of radiation of a volume scattering/absorption/attenuation coefficient. The radiative flux is reduced by a factor exp(-"optical_thickness") on traversing the path. The atmosphere optical thickness applies to radiation passing through the entire atmosphere. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the optical thickness applies at specific wavelengths or frequencies. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. Aerosol particles take up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the particles. The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. Phrase "assuming_cloud_free" means the cloud free fraction of the grid box.

Change Date: 12 Jun 2026, 12:53 p.m.

Change Date: 12 Jun 2026, 1:02 p.m.

atmosphere_optical_thickness_due_to_ambient_aerosol_particles_assuming_clear_sky 1 [UUUU] P07 id: QW5TE9YE
The optical thickness is the integral along the path of radiation of a volume scattering/absorption/attenuation coefficient. The radiative flux is reduced by a factor exp(-"optical_thickness") on traversing the path. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the optical thickness applies at specific wavelengths or frequencies. The atmosphere optical thickness applies to radiation passing through the entire atmosphere. The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. "Ambient_aerosol" means that the aerosol is measured or modelled at the ambient state of pressure, temperature and relative humidity that exists in its immediate environment. "Ambient aerosol particles" are aerosol particles that have taken up ambient water through hygroscopic growth. The extent of hygroscopic growth depends on the relative humidity and the composition of the particles. To specify the relative humidity and temperature at which the quantity described by the standard name applies, provide scalar coordinate variables with standard names of "relative_humidity" and "air_temperature". A phrase "assuming_condition" indicates that the named quantity is the value which would obtain if all aspects of the system were unaltered except for the assumption of the circumstances specified by the condition. "Clear sky" means in the absence of clouds.