The Ras al Hadd Jet:: Remotely sensed and acoustic Doppler current profiler observations in 1994-1995

被引:49
作者
Böhm, E
Morrison, JM
Manghnani, V
Kim, HS
Flagg, CN
机构
[1] CNR, Ist Fis Atmosfera, I-00133 Rome, Italy
[2] N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27695 USA
[3] Univ Massachusetts, Ctr Marine Sci & Technol, New Bedford, MA 02744 USA
[4] Brookhaven Natl Lab, Dept Appl Sci, Upton, NY 11973 USA
基金
美国国家科学基金会;
关键词
D O I
10.1016/S0967-0645(99)00034-X
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
The existence of a surface barotropic front-jet system at the confluence region off the eastern tip of Oman (Ras Al Hadd or RAH) is documented for 1994-1995 through advanced very high resolution radiometer (AVHRR) and acoustic Doppler current profiler (ADCP) observations. The thermal signature of this confluence is visible in 1995 between early May and the end of October, i.e., throughout the SW Monsoon and into the transition period between SW and NE Monsoons. The thermal characteristics are those of a NE-oriented front between cooler water of southern (upwelled) origin and warmer waters of northern Gulf of Oman origin. During the period when the thermal front is absent, ADCP data suggest that the confluence takes a more southward direction with Gulf of Oman waters passing RAH into the southeastern Oman coastal region. The thermal gradient is initially small (June-July) but later increases (August-October) into a front that exhibits small-scale instabilities. Surface current velocities within the jet, estimated by tracking these features in consecutive satellite images, are 0.5-0.7 m s(-1) and in remarkable agreement with concurrent ADCP retrievals in which the seasonal maximum in velocity is 1 m s(-1). ADCP observations collected during several US JGOFS cruises reveal a weakly baroclinic current in the confluence region that drives the waters into the offshore system. The fully developed jet describes a large meander that demarcates two counter-rotating eddies (cyclonic to the north and anticyclonic to the south of the jet) of approximately 150-200 km diameter. The southern eddy of this pair is resolved by the seasonally averaged, sea-level anomaly derived from TOPEX/Poseidon observations. During the SW Monsoon, the RAH Jet advects primarily cold waters along its path, but as soon as the wind system reverses with the transition to the intermonsoonal period, a warm current is rapidly established that advects the surface coastal waters of the Gulf of Oman offshore. In accordance with the interannual variation of the wind forcing phase, the reversal of the currents from NE to SW occurred earlier in 1994 than in 1995, confirming that the RAH Jet is integral part of the East Arabian Current. The transport of the Jet, estimated by combining SST information on the width with ADCP data on the velocity's vertical structure, is found to fluctuate between 2-8 x 10(6) m(3) s(-1) and its thickness between 150-400 m. These significant fluctuations are due to the time-variable partition of horizontal transport between eddies and the RAH Jet and are potentially important to the nutrient and phytoplankton budgets of the Arabian Sea. (C) 1999 Elsevier Science Ltd. All rights reserved.
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收藏
页码:1531 / 1549
页数:19
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