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Techniques - measurement techniq

Measurement techniques used in RADO

Active remote sensing

LIDAR - (Light Detection And Ranging) is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant target. The prevalent method to determine distance to an object or surface is to use laser pulses. Like the similar radar technology, which uses radio waves, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal.

Elastic backscatter lidar - uses elastic backscatter radiation to measure aerosol properties: altitude, dynamics, backscatter coefficient

Raman inelastic lidar - uses inelastic Raman (Nitrogen) backscatter radiation to extract aerosol properties: altitude, dynamics, extinction coefficient

Depolarization lidar - uses parallel and cross polarized backscatter radiation to discriminate between spherical and irregular scatterers and various aerosol classes (water droplets, cirrus particles, dust, smoke)

Differential absorption lidar - measures the backscatter signal from the atmosphere at two or more wavelengths where one is more strongly absorbed by a molecular species than another, to account for the number density of the absorber (e.g. ozone)

Multiwavelength lidar - uses a combination of channels at different wavelengths and various detection types to measure optical parameters of aerosols: backscatter and extinction coefficient, particle depolarization, color ratio, Angstrom coefficient, lidar ratio, AOD; microphysical parameters can also be calculated using accurate optical parameters at from 3 elastic and 2 inelastic Raman channels: size distribution, effective radius, complex refractive index, mass concentration.

Ceilometer - An automatic, active, remote-sensing instrument for detecting the presence of clouds overhead and measuring the height of their bases. For optically thin clouds, such as most cirrus, more than one layer may be detected, but when optically thick clouds, such as liquid water stratus, are present, the light beam is unlikely to penetrate much beyond the base of the lowest liquid layer. Laser ceilometers use intense pulses of light in a very narrowly collimated, vertically directed beam, and have collocated transmitter and receiver systems. The cloud base heights may be displayed in a variety of time-height section images or backscatter intensity profile plots. Some older ceilometers use separated transmitter and receiver units. The instruments are designed to work during the day or night.

Sodar - An acoustic radar (sodar) that can determine radial velocity (velocity toward or away from the sodar) of the air by measuring the frequency shift of the returning sound waves that were scattered from regions of turbulent fluctuations of air temperature, compared to the original transmitted frequency. Velocities within individual surface-layer plumes and the bottom of convective thermals can be measured. Most sodar signals are blown away in strong winds, and the sodar also requires acoustic shielding from outside noise such as from roads, towns, and rustling tree leaves.

Passive remote sensing

Satellite imagery (EUMETCAST) - consists of photographs of Earth or other planets made by means of artificial satellites. EUMETCast is a scheme for dissemination of various (mainly satellite based) meteorological data operated by EUMETSAT, the European Organisation for the Exploitation of Meteorological Satellites. EUMETCast includes data from Meteosat 7 (Indian Ocean), 8 and 9, derived products, data from polar orbiting satellites (Metop-A and NOAA-18 global coverage, NOAA-17 and NOAA-18 European regional coverage) and data from other meteorological programmes

Sun photometry - A sun photometer is a type of photometer conceived in such a way that it points at the Sun. Recent sun photometers are automated instruments incorporating a Sun-tracking unit, an appropriate optical system, a spectrally filtering device, a photodetector, and a data acquisition system. The measured quantity is called direct-Sun radiance. When a sun-photometer is placed somewhere within the Earth's atmosphere, the measured radiance is not equal to the radiance emitted by the Sun (i.e. the solar extraterrestrial radiance), because the solar flux is reduced by atmospheric absorption and scattering. Therefore, the measured radiant flux is due to a combination of what is emitted by the Sun and the effect of the atmosphere; the link between these quantities is given by Beer's law.

Microwave radiometry - A microwave radiometer (MWR) is a radiometer that measures energy emitted at sub-millimetre-to-centimetre wavelengths (at frequencies of 1-1000 GHz) known as microwaves. By understanding the physical processes associated with energy emission at these wavelengths, scientists can calculate a variety of surface and atmospheric parameters from these measurements, including air temperature, sea surface temperature, salinity, soil moisture, sea ice, precipitation, the total amount of water vapor and the total amount of liquid water in the atmospheric column directly above or below the instrument.


Mass spectroscopy

Aerodynamic and scattering

Light scattering

Point monitoring



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