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The primary source for the relative wind data was the PMEL "Skyvane" anemometer that was located at the top of the aerosol sampling mast. For periods of missing data from the PMEL data source the ships IMET SSSG wind sensor was used. We assume that the relative wind information is primarily used to determine periods of ship contamination, thus we are using the anemometer that is closest to the sample inlet. This anemometer also was used as an input to the algorithm that turned off the sample pumps during periods of ship contamination.)
The one second relative wind speed and direction data were separated into orthogonal components of "keel" and "beam". These components were averaged into 1 minute averages, and then recombined to relative wind vectors. Wind speed is reported meters per second and wind direction is in degrees with -90 being wind approaching the ship on the port beam, 0 degrees being wind approaching the ship directly on the bow, and +90 degrees being wind approaching the ship on the starboard beam.
Wind Components/ True Wind Speed/ True Wind Direction:
True wind speed and direction were calculated from measurements
obtained with
the Ships IMET wind sensor. This sensor was mounted 15.5 meters above the
sea
surface on the ship's meteorological sampling mast at the bow and
should be
less affected by bending of streamlines as the air moves over the ship.
(The
PMEL “Skyvane” was on the top of the Aero-Van and in the ‘perturbed
airflow’.)
The true North and East components of the wind vector from the 10
second
SCS data
were calculated and then averaged into 1 minute intervals in m/s. The
true wind
vector was calculated from these components and is given as wind speed
in m/s
and wind direction in compass degrees. The WindU and WindV are
the east and
north components of the wind vector (in m/s).
U.S.Dept of Commerce / NOAA / OAR / PMEL / Atmospheric Chemistry