Abstract

Currently most ocean forecast systems provide daily eddy resolving predictions 7 days or so in advance. We first investigate the potential for longer range daily ocean forecast up to 28 days using the coupled system ACCESS-S1 in which the ocean component is eddy permitting. The daily ocean forecasts over the hindcast period 1990–2012 in the Indo-Pacific oceans have been evaluated, using persistence skill as a reference. Our results show that the sea surface temperature (SST) biases are in the range of ±0.3 °C in most regions within the first 28 days of the forecast. The model’s predicted correlation skill of SST anomaly (SSTA) is higher than persistence skill in most areas beyond the first few days up until the 28-day lead time. The skill of SSTA indices averaged in different domains suggest that the model produces more skilful predictions in the North Indian Ocean, South Indian Ocean, western tropical Pacific and Leeuwin Current regions than the corresponding persistence forecasts. The model’s SSTA prediction skill in the eastern tropical Pacific is comparable to the persistence skill which is very high. The model’s correlation skill for sea surface height anomaly (SSHA) can beat persistence skill beyond the first week and the model’s skill has a great advantage with a longer lead time. The daily prediction of the larger mesoscale eddies that shed off the East Australia Current is also investigated here. The spatial correlation between the model predicted and observed SSHA is applied to measure the model prediction skill for these eddies. Our results suggest that the averaged correlation for all forecasting cases at the same lead time is above 0.5 up to 14-day lead. It indicates that ACCESS-S1 has some skill in predicting these eddies, since the strength and track of the eddies in the Tasman Sea are highly complicated.

摘要

当前，大多数海洋预报系统都提前7天左右提供每日涡旋解析预报。我们首先使用耦合系统ACCESS-S1（其中海洋成分是涡流允许的）调查长达28天的每日更长时间海洋预报的潜力。以持久性技巧为参考，对印度太平洋1990-2012年后播期的每日海洋预报进行了评估。我们的结果表明，在预报的前28天内，大多数地区的海表温度（SST）偏差在±0.3°C范围内。在最初的几天到28天的交货期之前，该模型在大多数地区的SST异常（SSTA）预测相关技能要高于持久性技能。在不同领域中平均得到的SSTA指数的技巧表明，该模型在北印度洋，南印度洋，热带西太平洋和吕温洋流地区产生的技巧预测要比相应的持久性预测高。该模型在热带东部太平洋地区的SSTA预测技能可与非常高的持续技能相媲美。该模型在海面高度异常（SSHA）方面的关联技能可以在第一周之后击败持久性技能，并且该模型的技能具有较大的优势，交货时间更长。在此还研究了东澳大利亚洋流产生的较大中尺度涡流的每日预测。将模型预测的SSHA与观察到的SSHA之间的空间相关性用于测量这些涡流的模型预测技能。我们的结果表明，在相同的交货时间下，所有预测案例的平均相关性在0.5天（直到14天）之前都高于0.5。这表明，由于塔斯曼海中涡流的强度和航迹非常复杂，ACCESS-S1在预测这些涡流方面具有一定的技巧。