National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2020

Global Tropical Moored Buoy Array: Wind Direction Accuracy Revisited

Freitag, H.P., M.J. McPhaden, and K.J. Connell

NOAA Tech. Memo. OAR PMEL-150, NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, 23, doi: 10.25923/bn0n-3g25, View online (2019)

Wind direction measurement accuracy for Global Tropical Moored Buoy Array (GTMBA) moorings deployed by Pacific Marine Environmental Laboratory (PMEL) was estimated by analysis of pre-deployment and post-recovery calibrations of compasses and anemometer vanes. The results of more than 4000 pre-deployment and post-recovery calibrations of Next Generation Autonomous Temperature Line Acquisition System (NX-ATLAS) compasses and anemometer vanes were compiled. More than 300 compass and vane calibrations of a newer PMEL mooring system (known as T-Flex) were also analyzed. NX-ATLAS ensemble wind direction accuracy was estimated to be 2.1° when moorings were first deployed, increasing to 6.6° when recovered due to calibration drift of both the compasses and vane. Three types of compasses were employed in NX-ATLAS moorings over the past two decades. Systems with the three compass types had nearly equal pre-deployment wind direction accuracy. Root-mean-square differences in compass calibration drift resulted in post-recovery wind direction accuracy ranging from 5.1° to 8.4° for the three compass types. T-Flex wind direction accuracy was estimated to be 2.7° at deployment and 3.4° when recovered, although the number of post-recovery calibrations was relatively small: 32 compass calibrations and 22 vane calibrations. The present composition of PMEL-deployed GTMBA moorings is about half NX-ATLAS systems and half T-Flex systems, with the number of T-Flex systems expected to increase in the future.

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