Short-term Measurements of Surface Currents Associated with the Alboran Sea Gyre during Donde Va?

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  • 1 Naval Ocean Research and Development Activity, NSTL, Bay St. Louis, MS 39529
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Abstract

During the period 6–18 October 1982, six flights by a U.S. Navy research aircraft were made over the Alboran Sea Gyre as part of the Donde Va? experiment. During five of these flights sonobuoys were dropped in a linear pattern designed to show the temporal and spatial variability of the currents that constitute the gyre. A normal development consisted of approximately 15 sonobuoys dropped along the longitudinal line 4°45′W from the Spanish coast to within 30 km of the Moroccan coast. During the following 4 hours, the sonobuoys were relocated twice, their positions noted, and their individual drift speeds and directions derived. Aircraft precision radiation temperature and aircraft expendable bathythermograph data were collected concurrently with the sonobuoy drops to determine the thermal structure of the water during the drift period. Inertial navigation winds, (at the 300-m altitude of the aircraft) as well as other meteorological data, were also collected. Analysis of these data shows that at the time of these flights the cold (∼17°C) waters along the outer portion of the Alboran Sea Gyre were the main constituent of the jet. These cold waters reached speeds of greater than 1.2 m s−1 as compared to average speeds of 0.6 m s−1 for the warmer water of the gyre. Examination of the aircraft meteorological measurements as well as data relating to the short-term atmospheric conditions (i.e., for the 12-day period of the study) do not indicate that meteorological factors had a major influence on the speed of the currents or the position of the gyre during the period of study.

Abstract

During the period 6–18 October 1982, six flights by a U.S. Navy research aircraft were made over the Alboran Sea Gyre as part of the Donde Va? experiment. During five of these flights sonobuoys were dropped in a linear pattern designed to show the temporal and spatial variability of the currents that constitute the gyre. A normal development consisted of approximately 15 sonobuoys dropped along the longitudinal line 4°45′W from the Spanish coast to within 30 km of the Moroccan coast. During the following 4 hours, the sonobuoys were relocated twice, their positions noted, and their individual drift speeds and directions derived. Aircraft precision radiation temperature and aircraft expendable bathythermograph data were collected concurrently with the sonobuoy drops to determine the thermal structure of the water during the drift period. Inertial navigation winds, (at the 300-m altitude of the aircraft) as well as other meteorological data, were also collected. Analysis of these data shows that at the time of these flights the cold (∼17°C) waters along the outer portion of the Alboran Sea Gyre were the main constituent of the jet. These cold waters reached speeds of greater than 1.2 m s−1 as compared to average speeds of 0.6 m s−1 for the warmer water of the gyre. Examination of the aircraft meteorological measurements as well as data relating to the short-term atmospheric conditions (i.e., for the 12-day period of the study) do not indicate that meteorological factors had a major influence on the speed of the currents or the position of the gyre during the period of study.

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