2004 LOM Workshop Monday 10:15 - 10:35 a.m.
Numerical Cabbeling of Dissipative and Monotone Tracer Advection Schemes
Mohamed Iskandarani, Eric Chassignet and Trevor J. McDougall
UM
miskandarani@rsmas.miami.edu
ABSTRACT
We investigate the spurious, and numerically induced, cabbeling caused by the inherent numerical dissipation of tracer advection schemes. This spurious cabbeling is the numerical analog of natural cabbeling, the process by which the nonlinear equation of states leads to denser water when water particles of nearly equal densities, but with different temperature and salt properties, mix. The spurious mixing can be exacerbated by the flux- and slope-limiting mechanisms used to prevent Gibbs oscillations from occuring. The impact of four classical advection schemes (Centered Difference, MPDATA, UTOPIA and WENO) on numerical cabbeling is studied. The experiment consists of advecting two passive tracers, that initially combine to yield a constant density, in a square basin driven by a double-gyre circulation. Most of the spurious cabbeling is caused by the deformational flow field, and occurs primarily in the western boundary current region and the eastward jet. Centered schemes with no numerical dissipation can lead to the production of negative anomalies, whereas only positive density anomalies are seen with dissipative schemes like WENO and UTOPIA. At coarse resolution, numerical cabbeling is most significant in deep layers with weak stratification, irrespective of the numerical scheme used.
2004 LOM Workshop Wednesday 1:10 - 1:30 p.m.
Performance of mixed layer models in HYCOM on the onset of the 1998 La Nina
BIROL KARA and ALAN WALLCRAFT
NAVAL RESEARCH LAB.
birol@nrlssc.navy.mil
ABSTRACT
The three K-profile vertical mixing models in HYCOM (KPP, Mellor-Yamada level 2.5, and GISS) all perform well enough that it is difficult to choose between them in a typical year or on typical individual events. The onset of the 1998 La Nina is one of the largest short term events (7 degC change is SST over 30 days) on record, and it is certainly the best observed with five equatorial buoys between 180W and 125W and several more at 2S or 2N. It has also proved difficult to replicate with ocean models, and is therefore an excellent test case for HYCOM and its mixed layer submodels. Our standard 26-layer 0.72 degree fully global (Arctic bipolar patch) HYCOM configuration, with KPP, was first spun up from Navy GDEM3 climatology for five years using ECMWF Reanalysis climatological forcing and then extended 1979-2001 using 6-hourly ECMWF forcing. No data assimilation or temperature relaxation was used, but SSS was relaxed to monthly GDEM3 values as a correction to the standard E-P and riverine surface salinity forcing. The June 1995 to December 1998 portion of this simulation was then repeated using Mellor-Yamada and GISS mixed layer submodels to study the El Nino/La Nina cycle. Note that the latitudinal grid size of this model is halved to 0.36 degrees near the equator to better resolve equatorial dynamics. We present the results of comparisons between the three twin simulations and observations for 1996-1998, and in particular for the 1998 La Nina onset in the central equatorial Pacific. The model--data comparisons were also extended to cover the time period from 1996 to 2001. Comparisons with 166 year--long daily SST buoy time series showed that while and KPP and GISS give median median RMS differences of 0.70 degC and 0.76 degC, respectively, MY2.5 gives median RMS difference of 0.85 degC during 1996-2001. TOPICS: e. mixed layer dynamics and mixed layer/layered model interactions h. model/model or model/data comparisons
2004 LOM Workshop Tuesday 1:20 - 1:40 p.m.
On the Mechanisms of Decadal Variability of the Wind-Driven Ocean Circulation
Peter Killworth, Andrew Hogg, Jeffrey Blundell, William Dewar
Southampton Oceanography Centre
p.killworth@soc.soton.ac.uk
ABSTRACT
Eddy resolving simulations of wind driven circulation in a large ocean basin are presented. A series of numerical experiments are used to demonstrate that the mean state and variability of the circulation is dependent upon the strength of ocean eddies, which in turn are controlled by parameters such as viscosity and bottom drag. In particular, strong modes of low-frequency variability arise in many parameter regimes, and these modes depend upon the presence of ocean eddies in the simulation. The dependence upon eddies may be due to either an eddy--mean flow feedback loop, or else may occur because of oscillations in the mean flow which contains strong nonlinear features due to the cumulative effect of the eddy field. Both of these possibilities are explored. In addition it is shown (using a coupled version of the model) that this intrinsic ocean variability may contribute to midlatitude climate variability.
2004 LOM Workshop Wednesday 3:20 - 3:40 p.m.
South Florida Regional HYCOM nested simulations
Villy Kourafalou, Roland Balotro, Alan Wallcraft and Tammy Townsend
University of Miami/RSMAS
villy@rsmas.miami.edu
ABSTRACT
The South Florida regional HYCOM model is an implementation of HYCOM around South Florida, from approximately 22.50N to 270N and from 790W to 840W, thus covering Florida Bay, the Florida Keys, the Florida Straits and parts of the southwest and southeast Florida shelf areas including the Dry Tortugas. The regional model has been nested (a) within the North and Equatorial Atlantic Ocean basin (NA) HYCOM and (b) within the Intra-American Seas (IAS) HYCOM. The minimum depth has been configured to 5m, with a 1m coastline. The simulations have been forced with perpetual year atmospheric forcing (monthly mean winds with 6-hour anomalies). River inputs have been specified for two west Florida shelf rivers: Shark River and Caloosahatchee River; the influence of low-salinity waters of Mississippi River origin are evident during summer. The shallow depths along the Florida Keys Reef Tract allow the propagation of eddies along the Florida Current front; enhanced eddy activity (as compared to the larger scale models) is also observed south of the Florida Current front. The regional model simulations reveal a wind-driven southeastward flow that is present in the Florida Straits along the Florida Keys shelf; this flow agrees well with drifter trajectories and with wind-driven events recorded in moored current meters. Movies of tracer dispersion help elucidate the pathways of passive tracers along and across the Florida Straits.
2004 LOM Workshop Wednesday 9:00 - 9:20 a.m.
A model study of the South Atlantic Ocean response to an anomalous heat flux forcing
Carlos Lentini, Reindert Haarsma, Edmo Campos, and Rainer Bleck
Instituto Oceanografico da Universidade de Sao Paulo
lentini@io.usp.br
ABSTRACT
An isopycnal coordinate ocean model coupled to an atmospheric model (SPEEDY-MICOM) has been used to investigate the response of this coupled system forced with anomalous heat fluxes on interannual time scales. The main focus of this work is to look for possible oceanic pathways linking the subtropical to the tropical region, as well as the role played by wave processes on propagating such anomalies. The model domain covers the area between 20N-45S and 65W-20E. The coupled model is spun up for the first 20 years before the atmospheric anomalous surface heat forcing is introduced. The ocean model is forced by heat flux anomalies imposed by the atmosphere which have the same spatial pattern of the subtropical South Atlantic dipole (Sterl and Hazeleger, 2003). SPEEDY-MICOM is forced by this dipole for 1 year. After that, the coupled system is free to evolve for the following 20 years. Ensemble means of forced and non-forced experiments are the basis of our results. Preliminary results show that advection by the mean flow and Rossby Wave dynamics are the two main ways of propagating the imposed anomalies away from its origin toward the South American east coast. Thermal subsurface anomalies are advected within the subtropical South Atlantic gyre by the mean flow, reaching the South American east coast in 4-5 years. No clear evidence of subsurface pathways linking the subtropical to the tropical region has been observed, as post-generated subsurface anomalies stayed within the subtropical gyre for the period of study. Westward propagating Rossby Waves not only introduce circulation anomalies to the mean flow, but they also seem to strongly influence the evolution of the intensity and the shape of the subsurface anomalies.
2004 LOM Workshop Wednesday 10:00 - 10:20 a.m.
Ocean forecast system for the North Atlantic: sensitivity studies.
Carlos Lozano, Ilya Rivin, D. B. Rao
NCEP
carlos.lozano@noaa.gov
ABSTRACT
A high resolution ocean forecast system for short term forecast in the North Atlantic based on the hybrid ocean model HYCOM is now under development at NCEP. As part of the model validation for the region, sensitivity studies to changes in forcing, geometry and parameterizations will be presented.
2004 LOM Workshop Tuesday 4:20 - 4:40 p.m.
Modelling the ocean circulation and the transformation of water masses over the Ross Sea Continental Shelf, including the Ross Ice-Shelf Cavity
Miguel Angel Morales Maqueda, David Holland
Courant Institute of Mathematical Sciences of New York University, New York, NY
maqueda@cims.nyu.edu
ABSTRACT
The isopycnic coordinate model MICOM is employed here to model the ocean circulation over the continental-shelf region of the Ross Sea and underneath the Ross Ice Shelf.Our goal is to determine the impact of ocean-ice shelf interactions on the transformation of water masses in the region.To avoid having to deal with problematic boundary conditions on the eastern Ross Sea, the model domain encompasses as well the continental-shelf areas all the way to the Antarctic Peninsula.Our model simulations suggest that year-to-year variability in the westward advection of relatively fresh waters from the Amundsen and Bellinghausen Seas into the Ross Sea has the potential to strongly affect the circulation and water properties both in the Ross Sea proper and beneath the Ross Ice-Shelf.
2004 LOM Workshop Monday 9:35 - 9:55 a.m.
Isopycnal, orthobaric and neutral coordinates
Trevor J McDougall
CSIRO Marine Research
Trevor.McDougall@csiro.au
ABSTRACT
The extent to which isopycnals, patched isopycnals, and orthobaric density surfaces attain the neutral property will be discussed and quantified. This leads into an evaluation of the quasi-non-material aspect of both orthobaric surfaces and neutral density surfaces (the quasi-non-material property causes flow across surfaces even in the absence of diabatic processes).
2004 LOM Workshop Tuesday 10:00 - 10:20 a.m.
Preliminary results for the interannual and decadal variability of a new UK coupled climate model
Alex Megann, Adrian New, Shan Sun, Rainer Bleck
Southampton Oceanography Centre
apm@soc.soton.ac.uk
ABSTRACT
The Coupled Hadley-Isopycnic Model Experiment (CHIME) comprises a new coupled model with a hybrid-coordinate ocean component (HYCOM) coupled to the Hadley Centre's HadAM3 atmospheric model. The ocean model is on a global spherical-bipolar grid with resolution 1.25 x 1.25 degrees in the spherical part of the domain, and has the Bering Strait open, while the atmosphere grid resolution is 2.5 degrees N-S and 3.75 degrees E-W. CHIME has the same atmosphere and an identical horizontal grid over most of the ocean model domain as the Hadley Centre's HadCM3 climate model but, with its isopycnal coordinate in the ocean interior, is expected to preserve water masses more faithfully while retaining adequate vertical resolution near the surface. CHIME therefore provides an excellent tool for evaluating the consequences of the choice of vertical coordinate for the ocean component of a coupled model. Preliminary results on the spinup and initial drift of the model will be presented, as well as an analysis of its interannual-decadal variability, which will be compared with corresponding results from HadCM3.
2004 LOM Workshop Wednesday 11:00 - 11:20 a.m.
Ensemble forecasting and the ocean's mesoscale
Arne Melsom
Norwegian Meteorological Institute
arne.melsom@met.no
ABSTRACT
A study using HYCOM has been conducted in order to assess the relative contributions to oceanic variability from (1) the deterministic response to atmospheric forcing and (2) the nondeterministic response due to flow instabilities. Two sets of ensemble simulations have been performed. The sets differ in the horizontal resolution, which were set to 9km (coarse resolution experiment, CRE) and 4.5km (fine resolution experiment, FRE), respectively. CRE and FRE are made up of 8 and 6 ensemble members, respectively. Individual members differ in their initial conditions only. Topics that will be discussed include (i) relations between model resolution and the degree of deterministic variability, (ii) no. of ensemble members and statistical convergence, and (iii) relations between deterministic variability and the magnitude of atmospheric forcing. More information can be found on the project's web site, http://ensemble.met.no
2004 LOM Workshop Wednesday 1:50 - 2:10 p.m.
Study of a hurricane induced coastally trapped wave using the HYbrid Coordinate Ocean Model (HYCOM)
E.J. Metzger, L.F. Zamudio, H.E. Hurlburt and P.J. Hogan
Naval Research Lab
metzger@nrlssc.navy.mil
ABSTRACT
The HYbrid Coordinate Ocean Model (HYCOM) has been used to study the propagation of a coastally trapped wave (CTW) along the Mexican west coast and into the Gulf of California (GoC). This wave was generated by Hurricane Juliette in September 2001. It is accurately simulated in a 1/12 degree Pacific basin version of HYCOM forced with winds from the Fleet Numerical Meteorology and Oceanography Center (FNMOC) Navy Operational Global Atmospheric Prediction System. Model-data comparisons of coastal sea level at Manzanillo, Mazatlan, Guaymas, Puerto Penasco and Cabo San Lucas clearly show the propagation of the CTW. Pacific HYCOM accurately simulates the phase of the signal, but the amplitude of the CTW is too weak. Finer resolution (1/25 degree and 1/37.5 degree) versions of nested GoC HYCOM within Pacific HYCOM more accurately simulate the amplitude of the wave suggesting high horizontal resolution is required to resolve this coastal signal. Sensitivity of the CTW to atmospheric hurricane forcing is also investigated by forcing nested GoC HYCOM with FNMOC 27 km resolution Coupled Ocean Atmosphere Prediction System wind stresses.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
Preliminar results on the SENSIVITY OF BIOPHYSICAL MODELING TO MODEL'S VERTICAL COORDINATE REPRESENTATION
M. Olascoaga, E Chassignet, J. Kindle, A. Wallcraft
RSMAS, U. M.
jolascoa@rsmas.miami.edu
ABSTRACT
A Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model is coupled to the Hybrid Coordinate Model (HYCOM) to make assessments of the sensitivity of plankton dynamics modeling to the choice of the model's vertical coordinate representation. An idealized two-dimensional domain (vertical cross section of a meridional channel with free surface and irregular bottom topography) is adopted for this study. The wind stress is chosen to produce upwelling (downwelling) in the west (east) channel's coast. HYCOM's flexibility to the vertical coordinate choice is exploited to perform numerical simulations using: (i) fixed z-levels, (ii) rho-coordinates (MICOM mode), (iii) following topography sigma-levels, and (iv) hybrid (z-, rho-, and sigma- coordinates) layers (standard HYCOM mode). Particular attention is paid to the effects of diapycnal mixing and mixed-layer representations on biophysical interactions modeling in the different experiments.
2004 LOM Workshop Tuesday 3:40 - 4:00 p.m.
Investigation of the Temporal and Spatial Variability of the North Atlantic Subtropical Mode Water Using Float Data and Numerical Model Results
Ge Peng, Eric Chassignet, Young-Oh Kwon, Stephen Riser
RSMAS/University of Miami
gpeng@rsmas.miami.edu
ABSTRACT
The properties of the North Atlantic Subtropical Mode Water (STMW), i.e., the 18-degree water (EDW), are calculated with float profiling observational data and ocean circulation model results. The basic characteristics of STMW are well documented in the literature from one time hydrographic sections or long term measurements at one location. Since the summer of 1997, up to 71 profiling floats were launched in the Western Subtropical North Atlantic region. The broad coverage in both time and space of the float profiles enables us to investigate the spatial and temporal variability of the STMW. In this study, we evaluate the performance of a North Atlantic numerical simulation against these float data, using the Miami Isopycnic Coordinate Ocean Model (MICOM). The good agreement between the two allows us to discuss the sensitivities of the float-derived results to observational sampling area and data coverage. Float-derived STMW properties are found to display more spatial variation when compared to the model-derived ones, even with the float profiles binned and mapped onto the model grid. Most variability of the model-derived STMW properties occurs at the northeast portion of the STMW domain and the least in the southeast. The spatial and temporal variability of model subduction rates and ventilation patterns will be described. The time series of domain averaged STMW temperature in both the model and observations do not show statistically significant seasonal and interannual variabilities while that of STMW volume displays a primary peak in the spring (March to May) each year and a secondary peak at October. Multi-year and decadal variabilities of the North Atlantic STMW properties (temperature, volume, subduction rate, etc.), and their relationship to the NAO will also be discussed using the model results.
2004 LOM Workshop Tuesday 3:20 - 3:40 p.m.
Characteristics of ventilation in ocean models
Kelvin Richards
IPRC/SOEST, University of Hawaii
rkelvin@hawaii.edu
ABSTRACT
The characteristics of ventilation of the thermocline is examined in models of the North Pacific and Atlantic oceans. The OGCM used in this study is MICOM, which maps comfortably onto conceptual models of the ventilation process. Both the pattern and rate of ventilation is found to be strongly dependent on the level of thickness diffusion in the model, with the sensitivity of the Atlantic being more than that of the Pacific. The results highlight the need for more consideration to be paid to the specification of lateral mixing in models used in climate studies. Comparison is made with the observed distribution of CFCs, demonstrating the difficulty in using such data to discriminate between ocean models.
2004 LOM Workshop Monday 11:10 - 11:30 a.m.
A Global Ocean Model Based on Icosahedral-Hexagonal Grids With a Hybrid Vertical Coordinate
Todd Ringler, David Randall, John Baumgardner, Don Stark, Bert Semtner
Colorado State University
todd@atmos.colostate.edu
ABSTRACT
This talk will present results from a new global ocean general circulation model (OGCM). The ocean model uses an icosahedral-hexagonal grid to tile the surface of the sphere and hybrid (floating) coordinates to discretize the vertical depth of the ocean. The use of icosahedral-hexagonal grids leads to a highly uniform and isotropic discretization of the sphere and eliminates problematic grid singularities found in other grid systems. The hybrid coordinate used to discretize the vertical direction spans the limits between an Lagrangian-coordinate, such as isopycnal coordinates, and an Eulerian-coordinate, such as z-level coordinates. As a result, the model can be integrated forward in time for several days using Lagrangian vertical coordinates to minimize vertical diffusion and dispersion. At fixed time intervals, the vertical layers are mapped back to z-level coordinates and the integration continues forward in time. This type of coordinate is referred to as an Arbitrary Lagrangian Eulerian coordinate and is being developed at LANL. The model contains much of the functionality of a full production ocean model including convective adjustment, implicit vertical mixing, UNESCO equation of state, realistic bathymetry, and sub-grid scale mixing parameterizations. The results show realistic ocean circulations using 40962 grids cells in the horizontal (nominal 1 degree grid) and 33 layers in the vertical. The ocean is forced using monthly mean NCEP wind stresses and restoring to Levitus temperature and salinity in the top 5 meter layer. The results demonstrate that not only is this a viable approach to ocean modeling, but also provides an alternative approach to overcome many of the classical problems in ocean modeling.
2004 LOM Workshop Wednesday 1:30 - 1:50 p.m.
Upper ocean response to Hurricane Isabel
Ilya Rivin, Carlos Lozano, Dan Iredell, D. B. Rao
NCEP
ilya.rivin@noaa.gov
ABSTRACT
Oceanic upper layer response to the passage of the Hurricane Isabel is examined using 1/12 degree Mercator HYCOM for the North Atlantic. We employ GISS parameterization for vertical mixing. The model is initialized from the Navy Research Laboratory nowcast for September 2, 2003 and forced by the NCEP Global Forecast System (GFS) analyses. The simulation results are compared with the observed data. The analysis is performed for three time periods: "pre-hurricane" (before hurricane passage), "hurricane", and "relaxation" after the hurricane land fall. Entrainment fluxes, deepening of the ocean mixed layer and currents response to the passing hurricane are analyzed.
2004 LOM Workshop Wednesday 11:20 - 11:40 a.m.
MULTIVARIATE DATA ASSIMILATION INTO HYCOM USING THE SEEK FILTER : IMPACT STUDIES
David Rozier, Florence Birol, Jean-Michel Brankart, Pierre Brasseur and Jacques Verron
LEGI, Grenoble, France
rozier@hmg.inpg.fr
ABSTRACT
An integrated system for simulation of ocean circulation with data assimilation, has been developed at LEGI, as a result of the European DIADEM/TOPAZ projects. It is based on a 1/3ยบ resolution North and Tropical Atlantic version of the HYCOM model. The assimilation scheme is a reduced-order Kalman filter derived from the Singular Evolutive Extended Kalman (SEEK) methodology. During the TOPAZ project, the SEEK assimilation scheme has been upgraded to incorporate in-situ measurements in addition to surface observations. The system is currently utilised in order to undertake various studies in the context of multivariate assimilation, whilst trying to understand better the mechanisms of assimilation and to pinpoint the current flaws of the methodology. A first set of studies examines the impact of various types of observations (sea-surface salinity data, mean dynamic topography, vertical temperature and salinity in situ profiles) within assimilation experiments. These impact studies illustrate particularly how sensitive the assimilation scheme is to quantitative and qualitative differences in the mean dynamic topography used in conjunction with observed sea-level anomalies. Secondly, experiments based on isolated observations are performed to understand better the assimilation mechanisms, identify any spurious effects such as artificially generated waves over large distances, and accordingly determine improvements of the assimilation method.
2004 LOM Workshop Monday 3:15 - 3:45 p.m.
HOME Architecture and Structure
Paul Schopf, Rainer Bleck, Eric Chassignet, Robert Hallberg, Roland deSzoeke, Alan Wallcraft
George Mason University
schopf@scs.gmu.edu
ABSTRACT
This talk will discuss the architectural problems confronting HOME. As an environment designed to replicate the precursor models while being built upon technologies such as the Earth System Modeling Framework (ESMF), a careful analysis of the extant codes, the ESMF standards, and desires for future functionality will need to be undertaken. This talk will discuss the currently- known problems confronting the team and the emerging strategies to solve them.
2004 LOM Workshop Wednesday 10:40 - 11:00 a.m.
A near real-time 1/12 degree Atlantic HYCOM nowcast/forecast system
Ole Martin Smedstad, Bruce Lunde, Harley E. Hurlburt, Alan Wallcraft, Eric Chassignet, Remy Baraille
Planning Systems, Inc., Stennis Space Center, MS 39259, USA
smedstad@nrlssc.navy.mil
ABSTRACT
A 1/12 degree Atlantic Ocean version of the HYbrid Coordinate Ocean Model (HYCOM) is used in a near real-time nowcast/forecast system. The model covers the region between 27S and 70N. The Modular Ocean Data Assimilation System (MODAS) sea surface height analysis of available satellite altimeter data is assimilated into the model. The surface information is projected in the vertical using the Cooper and Haines (JGR, 1996) technique. A relaxation to the MODAS SST analysis is also a part of the system. The model is currently run once a week to produce the nowcast. The run includes a 14 day forecast. The results from the system can be seen on the HYCOM Consortium web page at http://hycom.rsmas.miami.edu/. The results are compared to observations of frontal locations determined from independent MCSST observations. The frontal analysis is performed at the Naval Oceanographic Office. Independent observations from SeaWifs images are also used in the model-data comparisons. A series of images in the Gulf of Mexico in the summer and fall of 2003 show a very good agreement between the model sea surface height field and the pathway of the chlorophyll. The model results are also routinely compared to available profile data both from XBTs and the permanent PIRATA buoys in the equatorial Atlantic. This system is the first step toward a global 1/12 degree nowcast/forecast system based on HYCOM that is planned for transition to the Naval Oceanographic Office in 2006. The prediction system will provide boundary conditions for higher resolution coastal models. An accurate representation of the oceanographic fields at the open boundaries of a coastal model is important for a successful coastal ocean prediction system. More advanced assimilation techniques are in the process of being implemented/tested with HYCOM, e.g. a multivariate optimal interpolation scheme (MVOI) and the singular evolutive extended Kalman filter (SEEK).
2004 LOM Workshop Tuesday 9:20 - 9:40 a.m.
Representing Ocean-Bottom Pressure and Sea-Surface Height in Generalized Vertical Coordinate Ocean Models
Tony Song
Jet Propulsion Laboratory
song@pacific.jpl.nasa.gov
ABSTRACT
Satellite observations of ocean-bottom pressure (OBP) and sea-surface height (SSH) are fundamentally important information about ocean dynamics. Their proper representation in current community-user models is essential for model verifications and data assimilations. The GRACE OBP represents ocean mass changes, while the TOPEX SSH gives changes of water volume. Similarly, conventional z- or Sigma-coordinate models are volume-conserving, while true isopycnal-coordinate and non-Boussinesq models are mass-conserving. In the processes of developing hybrid-coordinate and generalized coordinate models, the data representation problem has to be resolved. This talk will focus on innovative numerical methods in generalized vertical coordinate models for better representation of bottom topography and non-Boussinesq physics. Successful long-term simulations of the Pacific Ocean and ENSO events will be presented.
2004 LOM Workshop Tuesday 11:30 - 11:50 a.m.
Sensitivity of climate simulations to mixing schemes in a coupled HYCOM/GISS model
Shan Sun
Goddard Institute for Space Studies, NASA
ssun@giss.nasa.gov
ABSTRACT
A new set of coupled model experiments are carried out with an improved version of the GISS AGCM, which includes a thermodynamic and dynamic ice model, and HYCOM. Two different surface layer mixing schemes, Kraus-Turner and KPP, are available. The talk focuses on the impact of different mixing parameterizations on the evolution of water masses and circulations as they affect conditions at the air-sea surface. We will also discuss some improvements in the global conservation in HYCOM.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
Estimating Salinity Profiles to Accompany XBT Data in the Gulf of Mexico and in the Gulf Stream
William Carlisle Thacker and Laurie Sindlinger
NOAA/AOML
carlisle.thacker@noaa.gov
ABSTRACT
In estimating salinity profiles that will accompany XBT data being assimilated into numerical models, the relationship between temperature and salinity for a specific region can be determined by the available CTD data. Salinity models can then be created from the CTD data at specific depths within a selected region. CTD data from the Gulf of Mexico and the Gulf Stream were used to begin exploring salinity models, but first, several procedures were necessary to give a more even sampling of the regions and to remove large outliers from the data.
2004 LOM Workshop Wednesday 2:10 - 2:25 p.m.
1/12 degree, Sigma-0 North Atlantic HYCOM Development
Tamara Townsend, Harley Hurlburt, Alan Wallcraft, Patrick Hogan
Naval Research Laboratory
townsend@nrlssc.navy.mil
ABSTRACT
Results from recent 1/12 degree, sigma-0 North Atlantic HYCOM experiments will be presented. These primarily involve elimination of the previously reported noise at this resolution in the weakly-stratified subpolar region. However, the results of additional developments will also be illuminated.
2004 LOM Workshop Monday 1:40 - 2:00 p.m.
HYCOM code development
Alan Wallcraft
NRL
Alan.Wallcraft@nrlssc.navy.mil
ABSTRACT
HYCOM is one of the generalized vertical coordinate ocean models that is a precursor to HOME (Hybrid Ocean Modeling Environment). The performance and features of HYCOM 2.2 will be described, as will plans for future development and preparation for HOME.
2004 LOM Workshop Wednesday 3:40 - 4:00 p.m.
Vertical Circulation Patterns Near the Florida Keys/Florida Bay Region
Jorge F. Willemsen, George Halliwell
RSMAS
jorge@rsmas.miami.edu
ABSTRACT
The development of float advection programs for HYCOM has had the interesting side effect of providing a capability to compute and diagnose the vertical velocity (w). We discuss the application of the extraction of w in a nested Keys/Bay domain supplied by Alan Wallcraft. Preliminary results show the presence of transient organized upwelling/downwelling cells as the Gulf Stream approaches the Florida Straits. The temporal and spatial variability will be demonstrated through a series of pictures. The numerical values are not unreasonable for the region.
2004 LOM Workshop Wednesday 11:40 a.m. - 12:00 noon
Development of a monitoring system for the Norwegian coastal zone environment
Nina Winther
Nansen Environmental and Remote Sensing Center
nina.winther@nersc.no
ABSTRACT
As a first step in building up a monitoring system for the Norwegian Coastal Zone Environment, a hindcast modelling system for this area is set up. The model system is a regional high resolution (~4km) model using the Hybrid Coordinate Ocean Model (HYCOM) for the North Sea, Skagerak and Kategat. The regional model receives realistic boundary conditions from larger scale models (the TOPAZ system) and has been run in a hindcast simulation for 1997 and 1998. The model results have been extensively validated using data from ship cruises, and results from this validation work will be presented. The presentation will focus on using HYCOM on a coastal application. This model system has also recently been set up in a forecast mode, producing 10-days forecast once a week. Evaluation of this forecast system will also be presented.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
A comparison of two vertical mixing schemes: Turner's vs. K-profile parameterization
Xiaobiao Xu, Eric Chassignet
RSMAS, Univ. of Miami
xbxu@rsmas.miami.edu
ABSTRACT
The ocean interior is characterized almost everywhere by very slow mixing, thus describing the diapycnal diffusion in our numerical models is straightforward. In some extreme case, for example, the gravity current generated by overflow of dense water from marginal seas, however, exhibit intense entrainment, double or even quadrupling their volume flux within a few days. Describing this vigorous entrainment is more difficult because it occurs across very sharp density gradients. And the entrainment is absolutely critical in determining the water mass properties that fill the open ocean. In isopycnal coordinate model frame, there are two options: Turner's (1986) and K-profile parameterization, both of them are Ri-dependent. In an idealized 2-D experiment, dramatically different results are found from these two schemes. Possible reasons are analyzed and short suggestion for improvement is presented.