At-sea real-time coupled four-dimensional oceanographic and acoustic forecasts during Battlespace Preparation 2007

Abstract

Systems capable of forecasting ocean properties and acoustic performance in the littoral ocean are becoming a useful capability for scientific and operational exercises. The coupling of a data-assimilative nested ocean modeling system with an acoustic propagation modeling system was carried out at sea for the first time, within the scope of Battlespace Preparation 2007 (BP07) that was part of Marine Rapid Environmental Assessment (MREA07) exercises. The littoral region for our studies was southeast of the island of Elba ( Italy) in the Tyrrhenian basin east of Corsica and Sardinia. During BP07, several vessels collected in situ ocean data, based in part on recommendations from oceanographic forecasts. The data were assimilated into a fourdimensional high-resolution ocean modeling system. Sound-speed forecasts were then used as inputs for bearing-and range-dependent acoustic propagation forecasts. Data analyses are carried out and the set-up of the coupled oceanographic-acoustic system as well as the results of its real-time use are described. A significant finding is that oceanographic variability can considerably influence acoustic propagation properties, including the probability of detection, even in this apparently quiet region around Elba. This strengthens the importance of coupling at-sea acoustic modeling to real-time ocean forecasting. Other findings include the challenges involved in downscaling basin-scale modeling systems to high-resolution littoral models, especially in the Mediterranean Sea. Due to natural changes, global human activities and present model resolutions, the assimilation of synoptic regional ocean data is recommended in the region.

Ocean and Coastal Modeling: Nonlinear Acoustic Propagation

“…On the west bank, Figure 21 indicates that the old SPH produces significantly higher storm surge at stations 18 and 19 with at maximum surge of 7.8 meters for the old SPH and a maximum surge of 5.0 meters for the new SPH. Unfortunately, stations [20][21][22] indicate that the surge has not yet peaked for the old SPH, indicating that the simulation ended before the maximum surge was captured. The new SPH produces a maximum surge of less than 4 meters at those locations.…”

Time-evolving acoustic propagation modeling in a complex ocean environment

“…Other MSEAS subsystems include: initialization schemes, nested dataassimilative tidal prediction; fast-marching coastal objective analysis ; stochastic sub-grid-scale models; data assimilation, optimization and adaptive sampling; dynamically-orthogonalequation for uncertainty predictions; non-Gaussian assimilation using Gaussian Mixture Models; machine learning of model structures and functions; and Lagrangian Coherent Structures. MSEAS has been used for multiple focused scientific studies in shelfbreak regions [4,23,[25][26][27][28][29][30]]. …”

“…Initial efforts that have coupled four-dimensional ocean fields with 2D acoustics modeling include data assimilation and uncertainty studies [31,32], end-to-end computations [33], real-time at-sea predictions [25] and coupled adaptive sampling [34]. …”

Recent Advances in Japanese Fisheries Science in the Kuroshio-Oyashio Region through Development of the FRA-ROMS Ocean Forecast System: Overview of the Reproducibility of Reanalysis Products

“…These initialized state variables, which can be considered to have been optimally estimated by combining observation and simulation, are generally referred to as "analysis" or "reanalysis" data. Such assimilated products are needed for many scientific and practical applications where realistic oceanographic conditions are required: in marine navigation systems used for transportation safety (e.g., [10]); for acoustic propagation forecasting (e.g., [11]); and in investigations of the transport of marine debris (e.g., [12] [13]), oil spills (e.g., [14] [15]), and radioactive materials (e.g., [16] [17]). …”