Climate Modelling Group
School of Earth and Ocean Sciences


NOAA Scripps Lamont Consortium on the Ocean's Role in Climate

TECHNICAL PROGRESS REPORT

To: Scripps Institution of Oceanography

For: NOAA Office of Global Programs

Subcontractor: University of Victoria

Semi-Annual Report: Report Period November 1, 1994 through April 30, 1995 (Due 2/15/95)

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Principal Investigator:
Dr. Andrew J. Weaver
School of Earth and Ocean Sciences
University of Victoria
PO Box 1700
Victoria, British Columbia
CANADA V8W 2Y2

tel: (250) 472-4001
fax: (250) 472-4004
e-mail: weaver@ocean.seos.uvic.ca
___________________________________________________________________

For your convenience you may complete this form and mail to JIMO, fax to 534-8041 or email to kheldman@ucsd.edu

Agency: National Oceanic and Atmospheric Administration, Office of Global Programs

Project Title: The Lamont/Scripps Consortium for Climate Research - Dynamical Modeling of Climate Change

NOAA Award No: NA47GP0188

Project Period: May 1, 1994 through April 30, 1997

Budget Period: November 1, 1994 through April 30, 1995

Performance Report Completed: February 2, 1995

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NOAA Programmatic Requirements: Progress reports shall contain brief (no longer than two pages) information on the following:

1) A comparison of actual accomplishments with the goals and objectives established for the period, the findings of the investigator, or both. Whenever appropriate and the output of programs or projects can be readily quantified, such quantitative data should be related to cost for computation of unit costs.
2) Reasons why established goals were not met, if appropriate.
3) Other pertinent information including, when appropriate, analysis and explanation of cost overruns or high unit costs.
Note: Recipients shall immediately notify Joint Institute for Marine Observations-Administrator 619-534-9668 of developments that have a significant impact on the award supported activities, problems, delays, or adverse conditions which materially impair the ability to meet the objectives of the award.

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Below I summarize the progress on the research funded through the NOAA Lamont/Scripps Consortium for Climate Research. I have also enclosed abstracts and a list of all publications which were supported through these funds. These abstracts provide more details on the individual research projects. Reprints will be submitted when the articles appear. One Nature News and Views piece recently appeared and a reprint is enclosed.

1) - Global Ocean Modelling

As stated in the last progress report, a global ocean model has been developed for coupling to the Canadian Climate Centre Atmospheric GCM. The coupling procedure is now well underway and the first fully-coupled modelling results should be available shortly. Using a version of this global ocean model, Weaver and Hughes (1995 an article submitted earlier this month) demonstrated the inevitability of using flux corrections in coupled models unless the basic physics (e.g. clouds) in the atmospheric component is better represented.

D. Robitaille, a PhD student working under my supervision, has introduced Freon into a hierarchy of models based on the GFDL OGCM: North Atlantic models with horizontal resolution of 1 degree by 1 degree and 2 degrees by 2 degrees; idealized North-Atlantic and two- hemisphere Atlantic models; a global model. He has further included an isopycnal mixing scheme with (Gent and McWilliams, 1990; Danabasoglu et al., 1994) and without (Redi, 1982) a parameterization ("bolus transport") of mixing associated with mesocale eddies. Experiments have been conducted (using Freon as a tracer) to test the strengths and weaknesses of the various sub-grid scale mixing parameterizations in the various model configurations. These results are currently being written up and will be submitted to Geophysical Research Letters next month.

A simple parameterisation of the sea surface temperature-evaporation feedback was also developed for use in uncoupled ocean models under mixed boundary conditions. The importance of the feedback was first tested in a couple of simple perturbation experiments, and then applied to three case studies featuring natural internal variability of the thermohaline circulation on decadal, century and millennial timescales. These results have been written up (in first draft stage) and should be submitted within a month.

2) - Finite-Element Modelling

This four year project involves a systematic procedure for model development. The last progress report outlined the main accomplishments to date. Since that time the barotropic finite element model has been tested in its global version. Time-dependent and nonlinear terms have also been included.

The model has initially been used to diagnose the transport of the North Atlantic (Myers et al. 1995). In this manuscript we suggest that the reason why 3-D ocean models do not get the Gulf Stream to separate at the correct latitude is due to a poor representation of the density field in the upper ocean. Research is also progressing well into the development of semi-Lagrangian advection algorithms appropriate for ocean models (e.g., Das and Weaver 1995). This latter paper was accepted for publication earlier this month.

Side by side, the thermocline equations (with Laplacian friction in the boundary layers) in Cartesian co-ordinates are continuing to be solved. Thierry Huck, recently arrived from Alain Colin de Verdière's group in France, is now working on this project.

3) - Energy Balance Atmosphere/ Ocean Coupled Modelling

The Energy-moisture balance model described in the last progress report has now been developed (Fanning and Weaver, 1995). This model has also been coupled to the Bryan-Cox GFDL (MOM Version). Initial experiments have focused on addressing the question as to whether or not ocean model resolution (and hence mesocale eddies) is important in oceanic heat transport. Results from these experiments suggest that the oceanic heat transport in the coupled system does vary dramatically with increasing resolution of the ocean model.

We further intend to reexamine the variability studies of Weaver et al. (1993) with the coupled EMBM/OGCM and to extend our coupled modelling experiments to the global domain.

4) - Coupled Ice/Ocean Modelling

Dr. Sheng Zhang has confirmed that he will arrive on July 1, 1995 to continue to work on this project. So far we have coupled a thermodynamic ice model to the zonally averaged ocean model discussed in section 5. Furthermore, a thermodynamic ice model is being coupled to the EBM/OGCM of section 3. A visiting student from the Netherlands (Mr. Geert Lenderlink) spent some time working on this project and he will write up his results shortly.

5) - Simple Coupled Models

Tang and Weaver (1995a), which was accepted a week ago, worked on a simple coupled ocean-atmosphere box model. Incorporating the idea of Weaver (1993), the atmosphere water transport in the model was calculated from the poleward heat flux budget, so that the thermohaline circulation/fresh water interaction could be studied. It was found in the coupled model that the present-day high-latitude sinking thermohaline circulation became increasingly unstable as the earth warmed, owning to the enhanced poleward fresh water transport.

Dr. Tang has extended this coupled box model study to a coupled zonally-averaged model. Being simpler but including the essential physics, the model is still being used to study the variability of the coupled system, the role of atmosphere freshwater transport, and mechanisms of climate drift. The ocean component of the coupled model is being used to study the parameter regimes of stability and variability in a two-hemisphere ocean (Tang and Weaver 1995b). These simple box model results are also now being compared with the EBM/OGCM results of section 3.

References:

Danabasoglu, G, J.C. McWilliams, & P.R. Gent, 1994: The role of mesoscale tracer transports in the global ocean circulation. Science, 264, 1123-1126.
Das, S.K. & A.J. Weaver, 1995: Semi-Lagrangian advection algorithms for ocean circulation models. J. Atmos. Ocean. Tech. in press.
Fanning, A.F., & A.J. Weaver, 1995: An Atmospheric Energy Moisture Balance Model: Climatology and Interpentadal Climate Change. J. Geophys. Res., submitted.
Gent, P.R. & J.C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr., 20,150-155.
Myers, P.G., A.F. Fanning & A.J. Weaver, 1995: On the cause of Gulf Stream separation in ocean models. J. Phys. Oceanogr., submitted.
Redi, M.H., 1982: Oceanic isopycnal mixing by coordinate rotation. J. Phys. Oceanogr., 12, 1154-1158.
Tang, B., & A. J. Weaver, 1995a: Climate stability as deduced from an idealized coupled atmosphere-ocean model. Clim. Dyn., in press.
Tang, B. & A. J. Weaver, 1995b: Stability and variability of the thermohaline circulation in two-hemisphere ocean models. To be submitted to J. Geophys. Res.
Weaver, A.J., and T.M.C Hughes 1995: Flux corrections in coupled ocean-atmosphere models. Clim. Dyn., submitted.
Weaver, A.J., J. Marotzke, P.F. Cummins & E.S. Sarachik, 1993: Stability and variability of the thermohaline circulation. J. Phys. Oceanogr., 23, 39-60.

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