Laser Scintillometers

The Scintec SLS Series Scintillometers are unique sensors which can measure atmospheric turbulence, heat flux, momentum flux and crosswind by purely optical means. The length of the measurement paths between the transmiiter and the receiver can be set up between 50 m and 250 m. Combined with a net radiometer, the SLS Series Scintillometers can determine the evaporation or evapotranspiration,

The models of the Scintec SLS Series are so-called inner-scale scintillometers. By measurering the spatial turbulence spectrum, they can directly asses the dissipation rate of turbulent kinetic energy. By application of Monin-Oboukhov similarity, this directly leads to the turbulent fluxes of heat and momentum without any complementing wind measurements or assumptions on surface roughness. Only the SLS Series Scintillometers provide the full set of assessible information purely from optical measurements: the structure function constant of refractive index C_n², the structure function constant of temperature C_T², the turbulent flux of heat, the turbulent flux of momentum, the inner scale of turbulence, the kinetic energy dissipation rate and the crosswind. If combined with a net radiometer, evaporation or evapotranspiration is also determined.

All SLS Series Scintillometers "ES" are eye safe Class 1 laser products.

Models

Surface Layer Scintillometer SLS20 (ES)

The Surface Layer Scintillometer for stable platforms or heavy tripods on solid ground.

heat flux, momentum flux by purely optical means

suitable for stable and unstable conditions

high temporal resolution

crosswind option available

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Surface Layer Scintillometer SLS20-A (ES)

The Surface Layer Scintillometer with beam steering which permits operation when manual beam alignment is undesirable or difficult.

built-in automatic beam steering

heat flux, momentum flux by purely optical means

high temporal resolution

crosswind option available

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Surface Layer Scintillometer SLS40 (ES)

The Surface Layer Scintillometer for operation on towers or other platforms prone to vibration.

correction for transmitter vibrations

suitable for stable and unstable conditions

beam-displacement calibration

crosswind option available

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Surface Layer Scintillometer SLS40-A (ES)

The Surface Layer Scintillometer for operation on towers or other platforms prone to vibration or longterm-drift.

built-in automatic beam steering

correction for transmitter vibrations

easy installation and operation

crosswind option available

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Competitive Advantages

Optical Measurement of Inner Scale and Momentum Flux

The Scintec SLS Series Scintillometers form a unique product line. They can optically measure the so-called inner scale of turbulence. Turbulence theory connects the inner scale to the dissipation rate of turbulent kinetic energy. Using Monin-Obukhov similary, an extensive set of quantities is derived: the structure function constant of refractive index C_n², the structure function constant of temperature C_T², the turbulent flux of heat, the turbulent flux of momentum, the inner scale of turbulence and the kinetic energy dissipation rate. In combination with a net radiometer, evaporation or evapotranspiration is also assessed. No additional wind measurements or assumptions on the roughness length are needed.

Spatially Representative Data

Scintillometers measure a path average between a transmitter and a receiver. This leads to representative data even in inhomogeneous terrain. The large footprint of a scintillometer contrasts with the small footprint of a conventional point sensor, which is solely determined by the fetch and largely dependent on wind direction and atmospheric stabilty..

High Temporal Resolution

The path averaging of a scintillometer reduces the need for temporal averaging when comparing to a conventional point sensor. This means that a scintillometer can produce statistically stable averages in much shorter times. As an estimate, one scintillometer can replace about 100 conventional point sensors for a similar statistical significance with identical averaging times. The adjacend graph shows an example: The SLS20 Scintillometer resolves a reduction in turbulent heat flux caused by a cloud-related drop in solar radiation. A single eddy-correlation sensor does not.

Double-Ended Remote Sensing

Scintillometers can easily measure over water, across a valley or over urban areas, for example, where the deployment of in-situ sensors would be troublesome.

No Flow Distortion

The path weighting functions of a scintillometer reaches zero at the transmitter and receiver positions. So there is virtually no distortion of the turbulent flow casued by the instruments themselves. This compares to point sensors, where a flow distortion correction is needed and often essential.

Crosswind Measurement Capacity

The Scintec BLS900, BLS2000 and all SLS Series Scintillometers can measure crosswind. This includes the sign or direction of the crosswind. So these instruments can also reliably measure crosswind with winds near the direction of the optical propagation paths.

Automatic Beam-Steering

The Scintec SLS20-A and SLS40-A have automatic transmitter beam steering. An optical scanning device points the transmitted beam automatically to the reveicer. This facilitates the transmitter align. It also allows operation from drifting platforms such as tripods on soft ground.

Built-in Vibration Correction

The Scintec SLS40 and SLS40-A use a duplicate set of detectors in order to quantify and correct for intensity variations caused by high-frequency transmitter movements on vibrating platforms. So the Scintec SLS40 and SLS40-A can be operated from towers, for example, which are prone to vibration.

Separate Storage Unit for Easy Data Access

All Scintec BLS and SLS Scintillometers store their measurement data in a designated Signal Processing Unit (SPU). The SPU is separate from the receiver and can be mounted in a location convenient for access to the data. Note that the receiver must be mounted so it points to the transmitter, usually on a tripod or another elevated platform, and may not be in easy reach.

Large Data Storage Capacity

All Scintec BLS and SLS Series Scintillometers have a data storage capacity of 6 GB which can hold large amounts of measurement and raw data. The measurement data storage period depends on the individual setting and can range from months to years.

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