Peter R Oke

The Commonwealth Scientific and Industrial Research Organisation | CSIRO · Oceans and Atmosphere

The East Australian Current (EAC) system includes a poleward jet that flows adjacent to the continental shelf, a southward and eastward extension, and a complex eddy field. The EAC jet is often observed to be subsurface intensified. Here, we explain that there are two factors that cause the EAC to develop a subsurface maximum. First, the EAC flows...

The ocean is the main heat reservoir in Earth’s climate system, absorbing most of the top-of-the-atmosphere excess radiation. As the climate warms, anomalously warm and fresh ocean waters in the densest layers formed near Antarctica spread northward through the abyssal ocean, while successions of warming and cooling events are seen in the deep-ocea...

Global estimates of absolute velocities can be derived from Argo float trajectories during drift at parking depth. A new velocity dataset developed and maintained at Scripps Institution of Oceanography is presented based on all Core, Biogeochemical, and Deep Argo float trajectories collected between 2001 and 2020. Discrepancies between velocity est...

Using data from Argo floats, satellite altimetry, and satellite sea surface temperature (SST), we investigate the merging of two anti‐cyclonic eddies in the Tasman Sea. The eddies are of different size and different density. Once the distance between the eddies falls below a critical separation distance, water from the smaller, denser eddy is obser...

Since the Argo program began, 568 floats returned almost 31,000 profiles, at high‐southern latitudes, with no measured position. These data are either disseminated with positions linearly interpolated between known positions, or with no geographic positions. Here, we present a simple method for estimating unknown Argo float trajectories. We try to...

Argo, an international, global observational array of nearly 4,000 autonomous robotic profiling floats, each measuring ocean temperature and salinity from 0 to 2,000 m on nominal 10-day cycles, has revolutionized physical oceanography. Argo started at the turn of the millennium, growing out of advances in float technology over the previous several...

BRAN2020 (2020 version of the Bluelink ReANalysis) is an ocean reanalysis that combines observations with an eddy-resolving, near-global ocean general circulation model to produce a four-dimensional estimate of the ocean state. The data assimilation system employed is ensemble optimal interpolation, implemented with a new multiscale approach that c...

Here we introduce a new tool, the Spectral Diagram (SD), for the comparison of time series in the frequency domain. The SD provides a novel way to display the coherence function, power, amplitude, phase, and skill score of discrete frequencies of two time series. Each SD summarises these quantities in a single plot for multiple targeted frequencies...

Forecast errors of subsurface temperature and salinity are substantially reduced with an efficient, two-step, multiscale Ensemble Optimal Interpolation (EnOI) system, applied to a near-global eddy-resolving ocean model. A critical element of any data assimilation system is the background error covariance, which for EnOI is typically a static ensemb...

Blue Maps aims to exploit the versatility of an ensemble data assimilation system to deliver gridded estimates of ocean temperature, salinity, and sea-level with the accuracy of an observation-based product. Weekly maps of ocean properties are produced on a 1/10°, near-global grid by combining Argo profiles and satellite observations using ensemble...

BRAN2020 is an ocean reanalysis that combines ocean observations with an eddy-resolving, near-global ocean general circulation model, to produce four-dimensional estimates of the ocean state. The data assimilation system employed is ensemble optimal interpolation, implemented with a new multiscale approach that constrains the broad-scale ocean prop...

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the wo...

In the past two decades, the Argo Program has collected, processed, and distributed over two million vertical profiles of temperature and salinity from the upper two kilometers of the global ocean. A similar number of subsurface velocity observations near 1,000 dbar have also been collected. This paper recounts the history of the global Argo Progra...

We introduce ACCESS-OM2, a new version of the ocean–sea ice model of the Australian Community Climate and Earth System Simulator. ACCESS-OM2 is driven by a prescribed atmosphere (JRA55-do) but has been designed to form the ocean–sea ice component of the fully coupled (atmosphere–land–ocean–sea ice) ACCESS-CM2 model. Importantly, the model is availa...

The operational Australian Bluelink ocean forecast system is used to transform physical oceanographic observations into coherent analyses and predictions. These analyses and predictions form the basis for information services about the marine environment and its ecosystem, and can provide boundary data for weather predictions. Bluelink information...

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the wo...

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the wo...

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the wo...

The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opport...

The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opport...

Ocean reanalyses combine ocean models, atmospheric forcing fluxes, and observations using data assimilation to give a four-dimensional description of the ocean. Metrics assessing their reliability have improved over time, allowing reanalyses to become an important tool in climate services that provide a more complete picture of the changing ocean t...

This paper summarizes recent efforts on Observing System Evaluation (OS-Eval) by the Ocean Data Assimilation and Prediction (ODAP) communities such as GODAE OceanView and CLIVAR-GSOP. It provides some examples of existing OS-Eval methodologies, and attempts to discuss the potential and limitation of the existing approaches. Observing System Experim...

The traditional view of the circulation in the Tasman Sea includes a coherent, quasi-zonal, eastward flow towards the northern tip of New Zealand that is widely referred to as the Tasman Front. This flow was first suggested in the 1960s by oceanographers reasoning that the source of volume transport “feeding” the East Auckland Current, around north...

The traditional view of the East Australian Current (EAC), as depicted in many schematics, is of a continuous boundary current that flows along the shelf off eastern Australia, between approximately 18°S and about 32.5°S, where it separates from the coast and continues either towards New Zealand, along the Tasman Front; or towards Tasmania, as the...

We introduce a new version of the ocean-sea ice implementation of the Australian Community Climate and Earth System Simulator, ACCESS-OM2. The model has been developed with the aim of being aligned as closely as possible with the fully coupled (atmosphere-land-ocean-sea ice) ACCESS-CM2. Importantly, the model is available at three different horizon...

Ocean data assimilation is increasingly recognized as crucial for the accuracy of real-time ocean prediction systems and historical re-analyses. The current status of ocean data assimilation in support of the operational demands of analysis, forecasting and reanalysis is reviewed, focusing on methods currently adopted in operational and real-time p...

The ocean circulation in the Great Australian Bight (GAB) is dominated by the surface-intensified Leeuwin Current (LC) over the outer continental shelf, and the Flinders Current farther offshore. In the GAB, the LC flows eastwards and varies seasonally, with strongest currents of up to 0.8 m/s (at 130.5°E), bringing warm and salty waters as far eas...

It is expected that the assimilation of data in an ocean model disrupts the model’s dynamical balance. This disruption occurs because the analysis fields are not a precise solution to the equations of the model. Therefore, the model adjusts to the applied increments. With this limitation in mind, we assess the impact of sequential data assimilation...

STDs overall tide gauges stations with significant data (17) separated by frequencies. Upper left: long-term band; Upper right: diurnal band; Lower left: semidiurnal band; and Lower right: M2 frequency. The model does a better job close to Townsville tide station for M2 frequency, diurnal and long-term bands.

STDs comparing sea-level from T8 and DFT with tidal gauge observations during DJF for an example in the A) Atlantic Ocean (Ilha Fiscal); B) Indian Ocean (Gan); and C) Pacific Ocean (Townsville) – showing the semidiurnal (yellow) and diurnal (green) averaged constituents for DFT (squares) and T8 (stars) at the end of the 10th (filled markers) and 20...

We introduce a new tool – the Spectral Taylor Diagram (STD) – for the comparison of time series in the frequency domain. The STD provides a novel way of displaying the squared-coherence, power, amplitude, phase, and root-mean-squared difference of discrete frequencies of two time-series. Each STD summarises these quantities in a single plot, for mu...

Vertical motions within eddies play an important role in the exchange of properties and energy between the upper ocean and the ocean interior. Here, we analyse alternating upward and downward cells in anticyclonic eddies in the East Australian Current region using a global eddy resolving model. The cells explain over 50% of the variance of vertical...

Apresentação dos resultados da tese e introdução ao Diagrama Espectral de Taylor desenvolvido pela autora. Apresentação oral no eixo temático Modelagem Geral em Cachoeira Paulista.

Using output from a near-global eddy-resolving ocean model, we analyse the properties and characteristics of quasi-isotropic eddies in five Western Boundary Current (WBC) regions, including the extensions of the Agulhas, East Australian Current (EAC), Brazil-Malvinas Confluence (BMC), Kuroshio and Gulf Stream regions. We assess the model eddies by...

Skillful marine biogeochemical (BGC) models are required to understand a range of coastal and global phenomena such as changes in nitrogen and carbon cycles. The refinement of BGC models through the assimilation of variables calculated from observed in-water inherent optical properties (IOPs), such as phytoplankton absorption, is problematic. Empir...

As with other Western Boundary Currents globally, the East Australian Current (EAC) is highly variable making it a challenge to model and predict. For the EAC region, we combine a high-resolution state-of-the-art numerical ocean model with a variety of traditional and newly available observations using an advanced variational data assimilation sche...

The technical steps involved in configuring a regional ocean model are analogous for all community models. All require the generation of a model grid, preparation and interpolation of topography, initial conditions, and forcing fields. Each task in configuring a regional ocean model is straightforward – but the process of downloading and reformatti...

This Explicit tidal forcing in OGCM (ocean general circulation models) using the eight dominant constituents of semidiurnal and diurnal tides in MOM5 (GFDL Modular Ocean Model version 5) plus accurate phase information is introduced. The main goal is to show the impact of tides in ocean dynamics focused on surface variables as sea surface temperatu...

Skilful marine biogeochemical (BGC) models are required to understand a range of coastal and global phenomena such as changes in nitrogen and carbon cycles. The refinement of BGC models through the assimilation of variables calculated from observed in-water inherent optical properties (IOPs), such as phytoplankton absorption, is problematic. Empiri...

Ocean boundary currents, transporting water masses and marine biota along the coastlines, are important for regional climate and marine ecosystem functions. In this study, we review the dominant multi-decadal trends of ocean boundary currents around Australia. Using an eddy-resolving global ocean circulation model, this study has revealed that the...

As with other western boundary currents globally, the East Australian Current (EAC) is inherently dynamic making it a challenge to model and predict. For the EAC region, we combine a high-resolution state-of-the-art numerical ocean model with a variety of traditional and newly available observations using an advanced variational data assimilation s...

Eddy-resolving global ocean models are highly desired for spatially-improved climate studies, but this is challenging because they require careful configuration and substantial computational resources. Model drift, partially related to insufficient model spin-up, imperfect model physics or bias in surface forcing, can be problematic, leading to con...

The technical steps involved in configuring a regional ocean model are analogous for all community models. All require the generation of a model grid, preparation and interpolation of topography, initial conditions, and forcing fields. Each task in configuring a regional ocean model is straight-forward – but the process of downloading and reformatt...

Using satellite altimetry and high-resolution model output we analyze the pathway of large, long-lived anticyclonic eddies that originate near the East Australian Current (EAC) separation point. We show that 25-30% of these eddies propagate southward, around Tasmania, leave the Tasman Sea, and decay in the Great Australian Bight. This pathway has n...

The East Australian Current (EAC) has a relatively weak mean flow and an energetic eddy field that dominates the circulation. The properties of the mean flow have been studied in detail, but the changes in the eddy field have received little attention. We analyze Argo temperature and salinity profiles for 2005-2012 to construct a picture of the tim...

The marine environment plays an increasingly important role in shaping economies and infrastructures, and touches upon many aspects of our lives, including food supplies, energy resources, national security and recreational activities. Global Ocean Data Assimilation Experiment (GODAE) and GODAE OceanView have provided platforms for international co...

The dramatic reduction in the number of observation data from the Tropical Atmospheric Ocean (TAO)/ Triangle Trans-Ocean Buoy Network (TRITON) array since 2012 has given rise to a need to assess the impact of those data in ocean Data Assimilation (DA) systems. This paper provides a review of existing studies evaluating the impacts of data from the...

The GODAE OceanView systems use various data assimilation algorithms, including 3DVar, EnOI, EnKF and the SEEK filter with a fixed basis, using different time windows. The main outputs of the operational data assimilation systems, the increments, have been compared for February 2014 in various regions. The eddy-permitting systems’ increments are si...

The value of global (e.g. altimetry, satellite sea-surface temperature, Argo) and regional (e.g. radars, gliders, instrumented mammals, airborne profiles and biogeochemical) observation-types for monitoring the mesoscale ocean circulation and biogeochemistry is demonstrated using a suite of global and regional prediction systems and remotely-sensed...

Under GODAE OceanView the operational ocean modelling community has developed a suite of global ocean forecast, reanalysis and analysis systems. Each system has a critical dependence on ocean observations - routinely assimilating observations of in-situ temperature and salinity, and satellite sea-level anomaly and sea surface temperature. This pape...

We present a new methodology that allows quantifying the impact of individual terms of the temperature and salinity conservation within the mixed layer on mixed layer depth (MLD). The method is applied to output from an ocean general circulation model in the Indian Ocean to investigate variability and changes in MLD. On seasonal timescales and for...

Ocean models are beneficial to many different applications, including industry, public-good, and defence. Many applications use high-resolution models to produce detailed maps of the ocean circulation. High-resolution models are historically time-consuming to configure – often taking weeks to months to properly prepare. A system for automatically c...

South Pacific subtropical density compensated temperature and salinity (spiciness) anomalies are known to be associated with decadal equatorial variability, however, the mechanisms by which such disturbances are generated, advect and the degree to which they modulate the equatorial thermocline remains controversial. During the late 1970's a climate...

We have performed a series of near-real-time observing system experiments with FOAM, the Met Office operational ocean forecasting system. These were conducted in parallel to the operational suite and identical to it except that certain observation types were excluded. At the start of each month the parallel system was reset to the operational resta...

The generation and evolution of eddies in the ocean are largely due to instabilities that are unpredictable, even on short time-scales. As a result, eddy-resolving ocean reanalyses typically use data assimilation to regularly adjust the model state. In this study, we present results from a second-generation eddy-resolving ocean reanalysis that is s...

Analysis of the variability of the last 18 yr (1993–2012) of a 32 yr run of a new near-global, eddy-resolving ocean general circulation model coupled with biogeochemistry is presented. Comparisons between modelled and observed mean sea level (MSL), mixed layer depth (MLD), sea level anomaly (SLA), sea surface temperature (SST), and {chla} indicate...

We have applied an ensemble optimal interpolation (EnOI) data assimilation system to a high resolution coastal ocean model of south-east Tasmania, Australia. The region is characterised by a complex coastline with water masses influenced by riverine input and the interaction between two offshore current systems. Using a large static ensemble to est...

Analysis of the variability in an 18-yr run of a near-global, eddy-resolving ocean general circulation model coupled with biogeochemistry is presented. Comparisons between modelled and observed mean sea level (MSL), mixed-layer depth (MLD), sea-level anomaly (SLA), sea-surface temperature (SST), and Chlorophyll a indicate that the model variability...

We define the footprint of an ocean observation as the region that is well correlated to the observed variable at zero time-lag. The footprint of observations from an observation array provides an indication of the region that is effectively monitored by that array. This study examines the footprint of moorings that underpin the Australian Integrat...

The Tasman Sea is unique - characterised by a strong seasonal western boundary current that breaks down into a complicated field of mesoscale eddies almost immediately after separating from the coast. Through a 16-year analysis of Tasman Sea eddies, we identify a region along the southeast Australian coast which we name ‘Eddy Avenue’ where eddies h...

We present a detailed description of TOPAZ4, the latest version of TOPAZ - a coupled ocean-sea ice data assimilation system for the North Atlantic Ocean and Arctic. It is the only operational, large-scale ocean data assimilation system that uses the ensemble Kalman filter. This means that TOPAZ features a time-evolving, state-dependent estimate of...

This paper compares the performance of operational short-range ocean forecast systems developed under the Global Ocean Data Assimilation Experiment (GODAE) – an international effort to demonstrate the feasibility of operational ocean forecasting. 'Best estimates' from four different operational forecast systems (either analyses, hindcasts, or nowca...

We present a detailed description of TOPAZ4, the latest version of TOPAZ - a coupled ocean-sea ice data assimilation system for the North Atlantic Ocean and Arctic. It is the only operational, large-scale ocean data assimilation system that uses the ensemble Kalman filter. This means that TOPAZ features a time-evolving, state-dependent estimate of...

We examine the role of dynamical instabilities and flow dependent, growing errors in an ensemble prediction study of the East Australian Current. In the region of the Tasman front where the East Australian Current separates from the coast, the circulation is characterised by me-andering and significant mesoscale eddy variability, and is dominated b...

The use of models and data assimilation tools to aid the design and assessment of ocean observing systems is increasing. The most commonly used technique for evaluating the relative importance of existing observations is Observing System Experiments (OSEs), and Observing System Simulation Experiments (OSSEs). OSEs are useful for looking back, to ev...

The poleward flowing East Australian Current (EAC) is characterised by its separation from the coast, 100–200 nautical miles north of Sydney, to form the eastward flowing Tasman Front and a southward flowing eddy field. The separation zone greatly influences coastal ecosystems for the relatively narrow continental shelf (only 15–50 km wide), partic...

During the Austral summer of 2006-07 a series of extreme oceanic events occurred in the Tasman Sea. Following a series of strong wind-driven upwelling events, an intense cold-core eddy developed off Sydney, Australia. A data-assimilating, eddy-resolving ocean model is used to create a three-dimensional time-varying reanalysis of these events. The r...

A new ensemble ocean data assimilation system, developed for the Predictive Ocean Atmosphere Model for Australia (POAMA), is described. The new system is called PEODAS, the POAMA Ensemble Ocean Data Assimilation System. PEODAS is an approximate form of an ensemble Kalman filter system. For a given assimilation cycle, a central forecast is integrate...