CMEMS General Assembly, 23 May 2019

Slides:



Advertisements
Similar presentations
INTERNAL WAVE GENERATION, BREAKING, MIXING AND MODEL VALIDATION ALAN DAVIES (POL) JIUXING XING (POL) JARLE BERNTSEN (BERGEN)
Advertisements

Numerical simulation of internal tides in the Sicily and Messina Straits Jihene Abdennadher and Moncef Boukthir Institut Preparatoire aux Etudes d’Ingenieur.
The physical environment of cobalt-rich ferromanganese crusts deposits, the potential impact of exploration and mining on this environment, and data required.
Salt rejection, advection, and mixing in the MITgcm coupled ocean and sea-ice model AOMIP/(C)ARCMIP / SEARCH for DAMOCLES Workshop, Paris Oct 29-31, 2007.
Mixing in Cold water Domes and at Sills Alan M. Davies and Jiuxing Xing Proudman Oceanographic Laboratory, Liverpool, UK.
HYCOM and the need for overflow/entrainment parameterizations.
Role of the Southern Ocean in controlling the Atlantic meridional overturning circulation Igor Kamenkovich RSMAS, University of Miami, Miami RSMAS, University.
Geophysical Fluid Dynamics Laboratory Review June 30 - July 2, 2009 Geophysical Fluid Dynamics Laboratory Review June 30 - July 2, 2009.
Modeling the M 2 and O 1 Barotropic and Baroclinic Tides in the Gulf of Mexico Using the HYbrid Coordinate Ocean Model (HYCOM) Flavien Gouillon 1 ; B.
Diagnosing Eddy Mixing in the Southern Ocean from SOSE Ryan Abernathey With John Marshall, Matt Mazzloff and Emily Shuckburgh.
Detecting and Tracking of Mesoscale Oceanic Features in the Miami Isopycnic Circulation Ocean Model. Ramprasad Balasubramanian, Amit Tandon*, Bin John,
Exploring strategies for coupled 4D-Var data assimilation using an idealised atmosphere-ocean model Polly Smith, Alison Fowler & Amos Lawless School of.
© Crown copyright Met Office UK report for GOVST Matt Martin GOVST-V, Beijing, October 2014.
Jiuxing Xing and Alan M. Davies
Internal Tides in the Weddell-Scotia Confluence Region, Antarctica Susan L. Howard, Laurence Padman, and Robin D. Muench Introduction Recent observations,
NEMO Developments and application at the Bedford Institute of Oceanography, Canada F. Dupont, Y. Lu, Z. Wang, D. Wright Nemo user meeting 2009Dalhousie-DFO.
1 Geophysical Fluid Dynamics Laboratory Review June 30 - July 2, 2009.
Japan/East Sea Hybrid Coordinate Ocean Model (HYCOM) Patrick J. Hogan and Harley E. Hurlburt Naval Research Laboratory, Code 7323, Stennis Space Center,
About the advantages of vertically adaptive coordinates in numerical models of stratified shelf seas Hans Burchard 1, Ulf Gräwe 1, Richard Hofmeister 2,
1.Introduction 2.Description of model 3.Experimental design 4.Ocean ciruculation on an aquaplanet represented in the model depth latitude depth latitude.
1-Slide Summary Explicit Southern Ocean eddies respond to forcing differently than parameterizations.  We need eddy resolving ocean climate models. Spurious.
NOCS: NEMO activities in 2006 Preliminary tests of a full “LOBSTER” biogechemical model within the ORCA1 configuration. (6 extra passive tracers). Developed.
Comparison of Different Approaches NCAR Earth System Laboratory National Center for Atmospheric Research NCAR is Sponsored by NSF and this work is partially.
High-resolution 3D modelling of oceanic fine structures using vertically adaptive coordinates Hans Burchard 1, Ulf Gräwe 1, Richard Hofmeister 2, Peter.
Internal Tide Generation Over a Continental Shelf Summer 2008 internship Gaёlle Faivre Flavien Gouillon, Alexandra Bozec Pr. Eric P. Chassignet.
Validation of decadal simulations of mesoscale structures in the North Sea and Skagerrak Jon Albretsen and Lars Petter Røed.
Ensemble-based Assimilation of HF-Radar Surface Currents in a West Florida Shelf ROMS Nested into HYCOM and filtering of spurious surface gravity waves.
“Very high resolution global ocean and Arctic ocean-ice models being developed for climate study” by Albert Semtner Extremely high resolution is required.
1) What is the variability in eddy currents and the resulting impact on global climate and weather? Resolving meso-scale and sub- meso-scale ocean dynamics.
Measuring the South Atlantic MOC – in the OCCAM ocean model Povl AbrahamsenJoel Hirschi Emily ShuckburghElaine McDonagh Mike MeredithBob Marsh British.
Joint OS & SWH meeting in support of Wide-Swath Altimetry Measurements Washington D.C. – October 30th, 2006 Baptiste MOURRE ICM – Barcelona (Spain) Pierre.
CHANGSHENG CHEN, HEDONG LIU, And ROBERT C. BEARDSLEY
Page 1© Crown copyright Modelling the stable boundary layer and the role of land surface heterogeneity Anne McCabe, Bob Beare, Andy Brown EMS 2005.
Role of internal wave mixing in coastal seas with sloping bottoms
Reduction of numerical mixing by means of vertically adaptive coordinates in ocean models Hans Burchard 1, Ulf Gräwe 1, Richard Hofmeister 2, Knut Klingbeil.
Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen.
Center for Ocean-Atmospheric Prediction Studies
15 Annual AOMIP Meeting. WHOI, 1- 4 November 2011 Numerical modeling of the Atlantic Water distribution in the upper Arctic Ocean: Sensitivity studies.
The effect of tides on the hydrophysical fields in the NEMO-shelf Arctic Ocean model. Maria Luneva National Oceanography Centre, Liverpool 2011 AOMIP meeting.
Seasonal Variations of MOC in the South Atlantic from Observations and Numerical Models Shenfu Dong CIMAS, University of Miami, and NOAA/AOML Coauthors:
Impacts of Vertical Momentum Mixing in an Arctic Ocean Model Youyu Lu 1, Greg Holloway 2, Ji Lei 1 1 Bedford Institute of Oceanography 2 Institute of Ocean.
I. Objectives and Methodology DETERMINATION OF CIRCULATION IN NORTH ATLANTIC BY INVERSION OF ARGO FLOAT DATA Carole GRIT, Herlé Mercier The methodology.
Intercomparison of ocean circulation in regional Arctic Ocean models at increasing spatial resolution – Preliminary Results Robert Osinski, Wieslaw Maslowski.
Coupling ROMS and CSIM in the Okhotsk Sea Rebecca Zanzig University of Washington November 7, 2006.
Our water planet and our water hemisphere
Jake Langmead-Jones The Role of Ocean Circulation in Climate Simulations, Freshwater Hosing and Hysteresis Jake Langmead-Jones.
Bruce Cornuelle, Josh Willis, Dean Roemmich
Enhancement of Wind Stress and Hurricane Waves Simulation
Coordinated mixing experiments
The Marine System Modelling group (MSM) at the UK's National Oceanography Centre (NOC) maintains and runs various NEMO configurations. Global, ocean-only,
Mesoscale eddies and shelf-basin exchange in the western Arctic Ocean
Grid Point Models Surface Data.
Seamless turbulence parametrization across model resolutions
OCEAN RESPONSE TO AIR-SEA FLUXES Oceanic and atmospheric mixed
Coupled atmosphere-ocean simulation on hurricane forecast
5th Workshop on "SMART Cable Systems: Latest Developments and Designing the Wet Demonstrator Project" (Dubai, UAE, April 2016) Contribution of.
Shelf-basin exchange in the Western Arctic Ocean
October 23-26, 2012: AOMIP/FAMOS meetings
Mark A. Bourassa and Qi Shi
WaveFlow KO Øyvind Breivik (MET Norway), Joanna Staneva (HZG), Jean Bidlot (ECMWF) and George Nurser (NOC)
Modeling the Atmos.-Ocean System
Models of atmospheric chemistry
Peter Lean1 Suzanne Gray1 Peter Clark2
RENUMERATE: Reducing numerical mixing resulting from applying tides explicitly in a global ocean model Alex Megann1 and Maria Luneva2 Project kickoff.
66-SE-CMEMS-CALL2: Lot-3 Benefits of dynamically modelled river discharge input for ocean and coupled atmosphere-land-ocean systems Hao Zuo, Fredrik Wetterhall,
What controls the time scale of Circumpolar Deep Water intrusions onto Antarctic continental shelves? Michael S. Dinniman Pierre St-Laurent John M. Klinck.
Numerical Mixing in the COSIMA Models
  Robin Robertson Lamont-Doherty Earth Observatory
The RENUMERATE project
Estimating ocean-shelf flux and exchange with drifters
Presentation transcript:

CMEMS General Assembly, 23 May 2019 RENUMERATE: Reducing numerical mixing resulting from applying tides explicitly in a global ocean model Alex Megann1 and Maria Luneva2 (1) National Oceanography Centre, Southampton, UK (2) National Oceanography Centre, Liverpool, UK CMEMS General Assembly, 23 May 2019

Project objectives and team presentation Adding tides to ocean models Motivation: benefits and downsides The global tidally forced model Preliminary mixing analysis Numerical mixing in fixed-coordinate models The z~ coordinate Further alleviation of numerical mixing Summary and next steps Projected impacts on CMEMS MFCs and TACs

Overall objectives of RENUMERATE project Objective 1: To add explicit tidal forcing to the GO8.0 global ¼° NEMO configuration and evaluate the effects on water mass characteristics and mixing.

Overall objectives of RENUMERATE project Objective 1: To add explicit tidal forcing to the GO8.0 global ¼° NEMO configuration and evaluate the effects on water mass characteristics and mixing. Objective 2: To add the z-tilde semi-lagrangian coordinate to this configuration and evaluate the effects on water mass characteristics and mixing, in particular to assess its effect in ameliorating numerical mixing from tidal and other high frequency motions.

Overall objectives of RENUMERATE project Objective 1: To add explicit tidal forcing to the GO8.0 global ¼° NEMO configuration and evaluate the effects on water mass characteristics and mixing. Objective 2: To add the z-tilde semi-lagrangian coordinate to this configuration and evaluate the effects on water mass characteristics and mixing, in particular to assess its effect in ameliorating numerical mixing from tidal and other high frequency motions. Objective 3 To investigate the effects of tides on large-scale ocean circulation, including global stratification, overturning and gyre circulations; shelf slope exchange, seasonal mixed layers, deep and bottom waters, and polar sea ice.

The RENUMERATE team Alex Megann Maria Luneva Interests: Interests: Model development, numerical mixing, vertical coordinate issues, ocean heat uptake Role in project: Overall PI; carry out model runs and evaluate them; lead on project deliverables Maria Luneva Interests: High latitude oceans, ocean mixing schemes, tides, vertical coordinate issues Role in project: Test tidal configurations and diagnostics; advice on tides and mixing; contribute to reports and papers

Why add tides to a global ocean model? Tidal motions close to ridges and rough bathymetry, along with breaking internal tides, cause strong mixing in the ocean; standard parameterisations of tidal mixing can only be an approximation, neglecting spatial distributions and link to circulation.

Why add tides to a global ocean model? Tidal motions close to ridges and rough bathymetry, along with breaking internal tides, cause strong mixing in the ocean; standard parameterisations of tidal mixing can only be an approximation, neglecting spatial distributions and link to circulation. Tidal flows are dominant source of mixing on shelves.

Why add tides to a global ocean model? Tidal motions close to ridges and rough bathymetry, along with breaking internal tides, cause strong mixing in the ocean; standard parameterisations of tidal mixing can only be an approximation, neglecting spatial distributions and link to circulation. Tidal flows are dominant source of mixing on shelves. Tides are responsible for a large part of transport of nutrients on and off shelves.

Potential downsides to including tidal forcing Large tidal velocities will stress stability of model numerics, especially in shallow shelf regions and over slopes.

Potential downsides to including tidal forcing Large tidal velocities will stress stability of model numerics, especially in shallow shelf regions and over slopes. Vertical motions from tides have potential to cause significant levels of numerical mixing in a depth-coordinate ocean model

Potential downsides to including tidal forcing Large tidal velocities will stress stability of model numerics, especially in shallow shelf regions and over slopes. Vertical motions from tides have potential to cause significant levels of numerical mixing in a depth-coordinate ocean model Most global models, with horizontal resolutions of 20-80 km and with 40-80 vertical levels, cannot realistically simulate the internal tide, and certainly not the explicit mixing from the latter.

Potential downsides to including tidal forcing Large tidal velocities will stress stability of model numerics, especially in shallow shelf regions and over slopes. Vertical motions from tides have potential to cause significant levels of numerical mixing in a depth-coordinate ocean model Most global models, with horizontal resolutions of 20-80 km and with 40-80 vertical levels, cannot realistically simulate the internal tide, and certainly not the explicit mixing from the latter. … but it’s still worth doing!

Adding tides to the GO8p0.1 global model Global NEMO configuration: horizontal resolution ¼° (10-27km) and 75 vertical levels. Closely related to ocean component of GC3.1 coupled model (used in CMIP6). Forced with M2, S2, N2, K1 and O1 tidal components. This is, to our knowledge, the first tidally-forced NEMO simulation in a realistic, eddy-permitting global domain.

First assessment of tidal motions GO8p0 tidal experiment GESLA analysis RMS hourly surface elevation excursion from the mean (metres) over three months in tidally-forced simulation (left) and M2 amplitude in GESLA analysis (right)

Numerical mixing in fixed-coordinate models Default vertical coordinate in NEMO is nonlinear free surface (z*): vertical levels are allowed to flex with external mode, but internal waves and internal tides will cause advection across coordinate surfaces. Advection schemes have a diffusive component, which leads to spurious numerical mixing (Griffies et al, 2000). This constitutes a substantial contribution to mixing in global ¼° NEMO configurations (Megann, Ocean Modelling, 2018) So we need to address numerical mixing to avoid tides adding to this

Quantification of numerical mixing We estimate effective diapycnal diffusivity keff in latitude bins and in density classes from the rate of watermass transformation (Lee et al, 2002; and Megann, 2018). To assess magnitude of numerical mixing, we compare keff in each experiment with: explicit vertical diffusivity kexp from model mixing scheme; and with diagnosed diffusivity keff in control. Augment this with global temperature drifts at each depth level. As expected, effective diffusivity is generally higher with tides than in control, particularly in intermediate and bottom water densities.

Tackling numerical mixing Introduce elasticity in vertical coordinate (z~) that flexes with disturbances of isopycnals on timescales less than a few days. Leclair and Madec (2011) found this reduced numerical mixing by a factor of ~5 in an idealized model. Have implemented z~ in the the global GO8p0 configuration. Vertical grid distortion associated with passage of large internal wave in NEMO with z~ scheme enabled (from Leclair and Madec, 2011)

Effects of z~ on mixing Adding z~ alone gives an unequivocal, though small (5-10%), reduction in effective diffusivity relative to control. Other changes to numerical scheme are being evaluated: More accurate (4th order) horizontal advection scheme; Increased viscosity to suppress poorly resolved, but persistent mesoscale features at higher latitudes, which are known to produce numerical mixing (Megann and Storkey, 2019); Increased filter cutoff time for z~ from 5 to 10 days

Preliminary results from sensitivity experiments All changes give reductions in effective diffusivity and in T drifts Largest improvements are from higher-order horizontal advection and increased viscosity Ratio of keff to keff in control Global mean temperature change between years 1 and 30

Achievements to date We have built and demonstrated the first global 3-D tidal model using NEMO at eddy-permitting resolution.

Achievements to date We have built and demonstrated the first global 3-D tidal model using NEMO at eddy-permitting resolution. The simulated barotropic tide is realistic in amplitude and spatial distribution.

Achievements to date We have built and demonstrated the first global 3-D tidal model using NEMO at eddy-permitting resolution. The simulated barotropic tide is realistic in amplitude and spatial distribution. We have installed and tested the novel z~ flexible vertical coordinate for the first time in a global model.

Achievements to date We have built and demonstrated the first global 3-D tidal model using NEMO at eddy-permitting resolution. The simulated barotropic tide is realistic in amplitude and spatial distribution. We have installed and tested the novel z~ flexible vertical coordinate for the first time in a global model. Preliminary analysis confirms that z~ offers a clear reduction in numerical mixing at little computational cost; other changes in numerical schemes offer promising further improvements.

Next steps Build improved tidal simulation with realistic shelf depths Complete 2-D and 3-D harmonic analysis of tidal simulation Evaluate shelf transports from tidal motions

Next steps Build improved tidal simulation with realistic shelf depths Complete 2-D and 3-D harmonic analysis of tidal simulation Evaluate shelf transports from tidal motions Quantify effect on run speed of numerical improvements

Next steps Build improved tidal simulation with realistic shelf depths Complete 2-D and 3-D harmonic analysis of tidal simulation Evaluate shelf transports from tidal motions Quantify effect on run speed of numerical improvements Combine numerical improvements with z~ to give optimised configuration

Next steps Build improved tidal simulation with realistic shelf depths Complete 2-D and 3-D harmonic analysis of tidal simulation Evaluate shelf transports from tidal motions Quantify effect on run speed of numerical improvements Combine numerical improvements with z~ to give optimised configuration Add tidal forcing to the latter, then repeat the above!

Benefits to Monitoring and Forecasting Centres (1) The work here is developing improvements to the NEMO ocean model, used in CMEMS operational systems, so results (in principle) are directly transferable to MFCs…

Benefits to Monitoring and Forecasting Centres (2) The simulation of tides will improve realism of ocean circulation in operational models, and hence will improve accuracy of forecasts. Specific examples include: Interaction between tides and sea ice has potential to enhance forecasting ability of the Arctic MFC. The presence of tidal transports on ocean shelves will improve the representation of shelf seas and biogeochemical fields (all MFCs)

Benefits to Monitoring and Forecasting Centres (3) The addition of the z~ coordinate and the optimisation of numerical schemes around it will further improve accuracy of forecasts. Specifically: We work closely with Mercator Ocean in Toulouse on improving the numerical performance of NEMO: this will feed directly into improvements in global models in the Global MFC. Minimising the numerical mixing associated with tidal motions will benefit all MFCs.

Benefits to Thematic Assembly Centres The development of a global, relatively high resolution 3-D ocean model with tides will be of interest to the Sea Level TAC