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Parameters calculated at RADO Da

Parameters calculated at RADO Data Center

Optical parameters

Extinction coefficient - Also called attenuation coefficient, especially in reference to radar frequencies.) is the fractional depletion of radiance per unit path length.  Extinction is caused by absorption and scattering. The extinction coefficient is the sum of the absorption coefficient and the scattering coefficient, and generally depends on wavelength and temperature.

Backscatter coefficient - A measure of the fraction of incident radiation that is scattered directly back toward the source.

Color ratio - Ratio of backscatter coefficient at different wavelengths

Angstrom exponent - is the name of the exponent in the formula that's usually used to describe the dependency of the aerosol optical thickness, or aerosol extinction coefficient on wavelength . The Angström exponent is inversely related to the average size of the particles in the aerosol: the smaller the particles, the larger the exponent. Thus, Angström exponent is a useful quantity to assess the particle size of atmospheric aerosols or clouds, and the wavelength dependence of the aerosol/cloud optical properties. For example, cloud droplet, usually with large sizes and thus very smaller Angström exponent (nearly zero), is spectrally neutral, which means, e.g., the optical depth does not change with wavelength. This exponent is now routinely estimated by analyzing radiation measurements acquired on Earth Observation platforms, such as AErosol RObotic NETwork, or AERONET.

Aerosol optical depth (AOD) - lidar and sun photometry - The optical depth due to extinction by the aerosol component of the atmosphere. Aerosol optical depths typically decrease with increasing wavelength and are much smaller for longwave radiation than for shortwave radiation. Values vary widely depending on atmospheric conditions, but are typically in the range 0.02–0.2 for visible radiation.

Particle depolarization coefficient - depolarization created by the particles only, calculated based on the ratio of the perpendicular and parallel component of the backscatter at the same wavelength

Microphysical parameters

Concentration - is the measure of how much of a given substance there is mixed with another substance. This can apply to any sort of chemical mixture, but most frequently the concept is limited to homogeneous solutions. For scientific or technical applications, a qualitative account of concentration is almost never sufficient; therefore quantitative measures are needed to describe concentration. There are a number of different ways to quantitatively express concentration. They are based on mass, volume, or both. Depending on what they are based on it is not always trivial to convert one measure to the other, because knowledge of the density might be needed to do so. At times this information may not be available, particularly if the temperature varies.

Mixing ratio - The ratio of the mass of a variable atmospheric constituent to the mass of dry air.

Size distribution - The amounts of different size particles of solids or liquids that are suspended in air as an aerosol. Particle size affects scattering of sunlight (see Rayleigh scattering and Mie scattering) that makes blue skies, white clouds, and hazy smog, and that affects visibility. Size affects the nucleation capability of particles to form cloud droplets due to both the curvature effect and the solute effect. Relative amounts of different particle sizes can be used as a tracer for an air mass, such as indicating whether it originated over continents, oceans, urban areas, or rural areas. The total abundance of particles is often proportional to the total number density of cloud droplets, which affects the size to which these droplets can grow and their resulting evolution.

Composition - Type and quantity of dissolved or suspended compounds in aerosol volume.

Meteorological parameters

Temperature - is a physical property that underlies the common notions of hot and cold. Celsius scale is used for most temperature measuring purposes.

Relative humidity - The ratio of the vapor pressure to the saturation vapor pressure with respect to water. This quantity is alternatively defined by the World Meteorological Organization as the ratio of the mixing ratio to the saturation mixing ratio.

Water vapor mixing ratio - Mixing or humidity ratio is expressed as a ratio of water vapor mass  per kilogram of dry air, at a given pressure.

Precipitations - is any product of the condensation of atmospheric water vapor that is pulled down by gravity and deposited on the Earth's surface. The main forms of precipitation include rain, snow, ice pellets, and graupel. It occurs when the atmosphere, a large gaseous solution, becomes saturated with water vapor and the water condenses, falling out of solution (i.e., precipitates). Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air.

Wind speed - the movement of air or other gases in an atmosphere. It is a scalar quantity, the magnitude of the vector of motion.

Wind direction - is the direction from which a wind originates. It is usually reported in cardinal directions or in azimuth degrees

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