Wetenschap - 15 januari 2015

SCINTILLOMETER CAN MEASURE SIDE WINDS ON RUNWAYS

tekst:
Roelof Kleis

Old technique put to new uses. Apparatus measures side wind all along runway. Side winds on airport runways can be disastrous.

Wind meters and weathervanes are therefore used to provide continuous information about the wind at particular points along the runway. Daniëlle van Dinther developed a method using scintillometers to measure the side wind along the entire length of the runway at the same time. This is a new application for an existing meteorological instrument. Scintillometers measure fluctuations in the degree to which light is broken up by scintillations in it. Scintillations are vortices in the air with a slightly different humidity and temperature. A scintillometer measure fluctuations in the signal caused by scintillations. These meters can also be used to measure side winds. What they actually measure then is the movement of vortices. According to Van Dinther, the principle has been known since the nineteen fifties. Two scintillometers next to each other measure the same scintillations one after the other. That time gap is a way of measuring the speed of the side wind. Until now, these signals had to be calibrated using measurements at ground level. Van Dinther developed a way of doing without that calibration.

Conservative

The main advantage of this new method of measuring wind, says Van Dinther, is that it is measured along the whole length of the runway. ‘Standard wind meters or vanes only measure it at one fixed spot. So theoretically, scintillometers provide more information. And it works, as measurements Van Dinther took at Schiphol show. But the apparatus can do a lot more than this. The scintillometer also detects the air turbulence caused by the aeroplanes themselves, the ‘wake vortex’ which is created near the wings especially. Van Dinther: ‘These vortices are dangerous for other planes. There are fixed norms for them, but with scintillometry you can just measure it. The air travel industry is conservative,’ thinks Van Dinther. ‘And all sorts of safety protocols have been developed. You don’t change those just like that. But there is certainly potential. We have proven that scintillometry can measure side winds.’


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