What averaging procedures are performed on the wind measurements?
Two wind averaging methods are used to calculate average wind speed and
For a comparison of vector and scalar averaging of winds, see:
- The first wind averaging technique applies to those measurements
reported by all DACT, VEEP, and ARES payloads. The average wind speed is
the simple scalar average of the wind speed observations. A
"unit-vector" average is used to calculate the average wind
direction. In this technique, unity serves as the length of the
vector, and the wind direction observations serve as the orientation
of the vector. The u and v components are then calculated for each
observation. Next, the average u and v components are computed and
the average wind direction is derived from "arctan(u/v)." Note that
this technique will produce greater wind speeds than if a true vector
average was used.
- The second method, used to calculate average speed and direction
reported by NDBC's older GSBP payloads, is a true vector average. In
this scheme, the magnitude of the vector is represented by the wind
speed observation and the direction observations are used for the
orientation. The vectors are then broken down into their u and v
components. All u and v components are then averaged separately. The
resulting average speed and direction are calculated from the
Pythagorean Theorem and "arctan(u/v)," respectively.
Gilhousen, D.B., 1987: A field evaluation of NDBC moored buoy
winds. Journal of Atmospheric and Oceanic Technology,4, 94-104.