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ALMA Memo #363
Velocity of the Effective Turbulence Layer at Chajnantor Estimated From 183 GHz Measurements

Guillermo Delgado and Lars-Ake Nyman

A linear relation between the turbulence layer speed and the ground wind speed was found indicating that the turbulence speed is roughly twice as high as the ground measured wind speed.

The temporal phase structure function was calculated, showing that the turbulence screen goes through a daily cycle associated with the insolation, with a well-defined layer structure at the extremes of the cycle.

The cross-correlation method allows the reliable measurement of the effective turbulence speed for about 90% of the day, apparently associated with the wind direction and the time when the turbulence layer is high up (the definition of “high up” is still uncertain). This implies that with a variation of this method, by moving the beams in the sky, we can continuously measure the height of the turbulence layer during most of the day, providing a very useful tool to assess the dynamics of the turbulence layer.

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Last modified: April , 2001