Cloud Properties - Microphysical

Measurements of various microphysical cloud properties.

Specific Measurements:

Backscattered radiation: The scattering of radiant energy into the hemisphere of space bounded by a plane normal to the direction of the incident radiation and lying on the same side as the incident ray.

Cloud condensation nuclei: Small particles (typically 0.0002 mm, or 1/100 th the size of a cloud droplet) about which cloud droplets coalesce.

Cloud droplet size: Linear size (e.g. radius or diameter) of a cloud particle

Cloud extinction: The removal of radiant energy from an incident beam by the process of cloud absorption and/or scattering.

Cloud ice particle: Particles made of ice found in clouds.

Cloud optical depth: Amount of light cloud droplets or ice particles prevent from passing through a column of atmosphere.

Cloud particle number concentration: The total number of cloud particles present in any given volume of air.

Cloud particle size distribution: The number of cloud particles present in any given volume of air within a specified size range, including liquid and ice.

Hydrometeor fall velocity: Fall velocity of hydrometeors (e.g. rain, snow, graupel, hail).

Hydrometeor Geometry: Measurements describing the geometry of hydrometeors, e.g. oblateness, diameters along different axes, volume, etc.

Hydrometeor image: Images of hydrometeors from which one can derive characteristics such as size and shape.

Hydrometeor optical properties: Optical properties of hydrometeors, including asymmetry factor, phase-function, single-scattering albedo, refractive index, scattering and absorption cross-sections, and backscatter fraction.

Hydrometeor phase: Hydrometeor phase such as liquid ice or mixed phase.

Hydrometeor size: The size of a hydrometeor, measured directly or derived from other measurements .

Hydrometeor Size Distribution: The number of hydrometeors observed in a given size range.

Ice nuclei: Small particles around which ice particles form.

Ice water content: The concentration (mass/vol) of ice water particles in a cloud.

Liquid water content: The concentration (mass/vol) of liquid water droplets in a cloud.

Liquid water path: A measure of the weight of the liquid water droplets in the atmosphere above a unit surface area on the earth, given in units of kg m-2.

Radar Doppler: The power spectrum and moments of the radar signal expressed as a function of Doppler frequency or Doppler velocity. It may be thought of as the reflectivity weighted radial velocity distribution of the scatterers in a distributed target.

Radar polarization: The temporal and geometric behavior of the electric field vector of an electromagnetic wave transmitted or received by a radar system, e.g. elliptical polarization, differential reflectivity, phase shift, co-polar correlation coefficient, linear depolarization ratio.

Radar reflectivity: A measure of the efficiency of a radar target in intercepting and returning radio energy. It depends upon the size, shape, aspect, and dielectric properties of that target.

Total cloud water: The total concentration (mass/vol) of ice and liquid water particles in a cloud; this includes condensed water content (CWC).


Radiometric terms for the IASOA data vocabulary are taken from the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) program’s measurement vocabulary. For the full reference, please visit: