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High and medium resolution ocean models for the Great Barrier Reef
Ocean Modelling ( IF 3.1 ) Pub Date : 2020-01-01 , DOI: 10.1016/j.ocemod.2019.101507
Frank Colberg , Gary B. Brassington , Paul Sandery , Pavel Sakov , Saima Aijaz

Abstract This article describes 3D medium (4km) and high (500m) horizontal resolution ocean models developed for the Coral Sea with a particular focus on the Great Barrier Reef lagoon. The medium resolution model is underpinning a 10 year reanalysis and a forecast demonstrator system for maritime monitoring. The ocean models have been developed to assist the management of the Great Barrier Reef given the existence of a number of stressors acting on the reef. The presented models aim to represent physical stressors that include thermal, salinity and flooding rivers. The river discharge is tracked by passive and age tracers. They can provide concentrations to identify the area/volume influenced by flood water. This paper gives an overview of the forward non-linear models with the aim to assess their performance. The models have been evaluated over a two year period spanning January 2009–March 2011 including the 2010/2011 La Nina and the advent of Tropical Cyclone Yasi in early 2011 that contributed to one of the largest river discharge events recorded over northern Queensland. The models’ performance is investigated on a full domain scale via means of satellite sea surface temperature (SST), expendable bathythermograph (XBT) and drifter data. Over the shelf and the Great Barrier Reef lagoon, available tide gauges, Ocean Colour, Chlorophyll-a and Queensland’s Integrated Marine Observing System (QIMOS) mooring data of temperature, salinity and velocity have been used to assess the models. Results suggest that the high resolution model gives better statistics in terms of mean absolute deviation and bias compared to the medium resolution model for subsurface temperature and salinity over the deep ocean. Moreover, sea surface temperature performance is similar for both models. Over the lagoon and shelf both models’ performance is mixed. The high resolution model displays a consistent warm bias on the order of 0.3 °C over the shallow well mixed stations throughout the year. However, the 4km model displays larger variability in this region. It tends to be too warm in summer and too cool in winter when compared to moorings. Modelled velocities are assessed via means of the QIMOS moorings. Overall the high resolution model fares better in terms of current direction with an average veering of 13° vs. 22°. The models’ performance is comparable in terms of current speed over the shallow moorings. However, the high resolution model is better equipped to represent steeper shelves and this results at times in better performance for velocity and temperature, particularly over Palm Passage. A large focus has been placed on including and assessing passive tracer dynamics emanating from river discharge. 25 river sources have been added across the models domain together with a set of one-dimensional channels representing the volume flux of brine. Two case studies are presented to demonstrate the models’ ability to reproduce mean features of observed plumes. A major river discharge event has been examined in further detail. Both models are able to reproduce the low salinity signal present in the observations in the upper level to a satisfactory degree. The 4km model matches the observed strength and duration of the fresh water plume substantially better than the high resolution model in this case.

中文翻译:

大堡礁的高分辨率和中分辨率海洋模型

摘要 本文描述了为珊瑚海开发的 3D 中(4km)和高(500m)水平分辨率海洋模型,特别关注大堡礁泻湖。中等分辨率模型支持 10 年再分析和海上监测预报示范系统。鉴于存在许多作用于大堡礁的压力源,已开发海洋模型以协助管理大堡礁。所提出的模型旨在代表物理压力因素,包括热量、盐度和洪水泛滥的河流。河流流量由被动和年龄示踪剂跟踪。它们可以提供浓度以识别受洪水影响的面积/体积。本文概述了前向非线性模型,旨在评估其性能。这些模型已在 2009 年 1 月至 2011 年 3 月的两年期间进行了评估,包括 2010/2011 年拉尼娜现象和 2011 年初热带气旋亚西的出现,这促成了昆士兰北部记录的最大河流流量事件之一。通过卫星海面温度 (SST)、消耗性海温仪 (XBT) 和漂移数据,在全域范围内研究模型的性能。在大陆架和大堡礁泻湖上,可用的潮汐计、海洋颜色、叶绿素-a 和昆士兰综合海洋观测系统 (QIMOS) 的温度、盐度和速度系泊数据已用于评估模型。结果表明,与深海地下温度和盐度的中等分辨率模型相比,高分辨率模型在平均绝对偏差和偏差方面提供了更好的统计数据。此外,两种模型的海面温度性能相似。在泻湖和货架上,两种型号的性能好坏参半。高分辨率模型在全年浅井混合站上显示出 0.3 °C 量级的一致暖偏差。然而,4km 模型在该区域显示出更大的可变性。与系泊设施相比,它往往在夏天太热,在冬天太凉。模拟速度通过 QIMOS 系泊设备进行评估。总体而言,高分辨率模型在当前方向方面表现更好,平均转向为 13° 与 22°。就浅层系泊处的当前速度而言,这些模型的性能相当。然而,高分辨率模型更适合表示更陡峭的货架,这有时会导致更好的速度和温度性能,特别是在棕榈通道上。主要关注包括和评估河流排放产生的被动示踪剂动态。在模型域中添加了 25 个河流源以及一组代表盐水体积通量的一维通道。提供了两个案例研究来证明模型重现观察到的羽流的平均特征的能力。已进一步详细检查了一次重大的河流泄洪事件。两种模型都能够令人满意地再现上层观测中存在的低盐度信号。
更新日期:2020-01-01
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