Airflow distortion at instrument sites on the RV "Tangaroa"

Accurate wind speed measurements from anemometers on research ships are required to obtain high quality air-sea flux measurements. However, the measurements can be biased by the distortion of the airflow over the ship, i.e. the wind speed can either be accelerated or decelerated by the presence of the ship. The computational fluid dynamics software VECTIS is used here to numerically simulate the airflow over the RV Tangaroa. The airflow distortion at ten anemometer sites has been quantified for a wind speed of 10 ms -1 blowing a) directly over the bows of the ship, b) from ±15 degrees and c) ±30 degrees off the bow. The wind speed errors ranged from decelerations of about 5 % at well-exposed bow locations to decelerations of close to 70 % in the turbulent wake region downwind of the ship’s superstructure. Three anemometers located above the bridge top experienced wind speed increases of between 4 % and 16 % of the free stream, or undistorted, wind speed.