Coupled Climate System Data Assimilation (Max Planck Fellow)

 

Group leader:

 

Prof. Dr. Detlef Stammer

Email: detlef.stammer@we dont want spamzmaw.de

Phone: +49 (0)40 42838 5052 / 7599

Fax: +49 (0)40 42838 7063

 

Group members:

 

Dr. Neeraj Agarwal - Email

Peter Herrmann (passed away on 1 April 2011)

Iuliia Polkova (PhD candidate) - Email

 

 

About the figure:

Oceanic state estimation is a powerful tool to estimate internal model parameters simultaneously with the model's initial conditions and surface forcing field that jointly would bring a model into consistency with time-varying large-scale ocean observations. The figure shows an example of the resulting spatially varying vertical diffusivity as it results from an attempt to estimate geographically varying fields of horizontal and vertical viscosity and diffusivity within a 9-year long estimation procedure. The figure shows the adjustment of the vertical diffusivity, δκv at 610m depth, after its normalization by the background value. Contour interval is 0.1. The resulting estimated coefficients are highly efficient in preserving water mass characteristics and frontal structures by reducing the models temperature and salinity drift, especially around the southern ocean. The estimated mean circulation results in stronger transports of western boundary currents and of the Antarctic Circumpolar Current. Moreover, an increase of about 10 % in the strength of the Meridional Overturning Circulation (MOC) and in the poleward heat transport can be found. Estimated changes in the horizontal mixing coefficients seem to agree with the notion that diapycnal mixing is superficially high with Laplacian mixing formulations, especially close to frontal structures in the ocean. In comparison with adjustments in tracer diffusivities (vertically and horizontally), adjustments of viscosity coefficients are fairly minor outside lateral boundary regions, suggesting that state estimation attempts might be most successful in providing enhanced insight into tracer mixing.

 

Research Objectives

This research group was founded as part of the Max Planck Fellow Program in order to strengthen the cooperation between the Max Planck Society and universities. The group is led by Prof. Dr. Detlef Stammer, University of Hamburg.

The working group aims at improving coupled climate models (ocean-ice-atmosphere-land) by applying dynamically consistent data assimilation. Through this method, data assimilation through a model data combination can help to improve uncertain model parameters and to estimate initial conditions for predictions. The results can then be used to better assess global and regional climate variations - than this could be done through data or models only - and to better analyze feedback mechanisms between climate components and sensitivities.

Accordingly, the group intends (1) to improve climate models through parameter optimizations and (2) to increase the predictive skill of coupled climate models through estimating improved initial conditions and by applying refined initialization methods. For both objectives, it is necessary to develop a coupled assimilation system in support of seasonal to decadal predictions that is dynamically self-consistent with the coupled model used for performing the prediction. It also requires an improved and expanded use of satellite data in the fields of climate modeling and climate system data assimilation. To be successful, experiences in running and understanding coupled climate system models are required as well as profound understanding of the sensitivity of climate models with respect uncertain model parameters.

Publications

Stammer, D., 1997a: Global characteristics of ocean variability from regional TOPEX/POSEIDON altimeter measurements. J. Phys. Oceanogr., 27, 1743-1769.

Stammer, D., 1997b: Steric and wind-induced changes in TOPEX/POSEIDON large-scale sea surface topography observations, J. Geophys. Res., 102, 20,987-21,010.

Stammer, D., 1998: On eddy characteristics, eddy transports and mean flow properties. J. Phys. Oceanogr., 28, 727-739.

Ponte, R. M., D. Stammer, and J. Marshall, 1998: Oceanic signals in observed motions of the Earth's pole of rotation. Nature, 391, 476-479.

Marotzke, J., R. Giering, Q. K. Zhang, D. Stammer, C. N. Hill, and T. Lee, 1999: Construction of the adjoint MIT ocean general circulation model and application to Atlantic heat transport sensitivity. J. Geophys. Research, 104, 29,529 - 29,548

Ponte, R.M., and D. Stammer, 2000: Global and regional axial ocean angular momentum signals and length-of-day variations (1985-1996). J. Geophys. Res., 105, 17,161-17,171.

Stammer, D., C. Wunsch, R. Giering, C. Eckert, P. Heimbach, J. Marotzke, A. Adcroft, C.N. Hill, and J. Marshall, 2002: The global ocean circulation during 1992 - 1997, estimated from ocean observations and a general circulation model. J. Geophys. Res., 107(C9), 3118, doi:10.1029/2001JC000888.

Stammer, D., K. Ueyoshi, A. Köhl, W.B. Large, S. Josey, and C. Wunsch, 2004: Estimating Air-Sea Fluxes of Heat, Freshwater and Momentum Through Global Ocean Data Assimilation. J. Geophys. Res., 109, C05023, doi:10.1029/2003JC002082.

Barnett, T., R. Malone, W. Pennell, D. Stammer, B. Semtner, and W. Washington, 2004: The effects of climate change on water resources in the west: Introduction and overview. Climate Change, 62, 1-11, DOI 10.1023/B:CLIM.0000013695.21726.b8.

Bengtson, L., P. Arkin, P. Berrisford, P. Bougeault, C. K. Folland, C. Gordon, K. Haines, K. I. Hodges, P. Jones, P. Kallberg, N. Rayner, A. J. Simmons, D. Stammer, P. W. Thorne, S. Uppala and R. S.Vose, 2007: The Need for a Dynamical Climate Reanalysis. Bulletin of the American Meteorological Society, 88, 495-501.

Pohlmann, H., J. Jungclaus, J. Marotzke, A. Köhl, and D. Stammer, 2009: Improving Predictability through the Initialization of a Coupled Climate Model with Global Oceanic Reanalysis. J. Clim., 22, 10.1175/2009JCLI2535., p. 3926 - 3938.

Balmaseda, M.A., O.J. Alves, A. Arribas, T. Awaji, D. Behringer, N. Ferry, Y. Fujii, T. Lee, M. Rienecker, T. Rosati and . Stammer, 2009: Ocean Initialization for Seasonal Forecasts. Oceanography, 22, 154-159.

Meehl, G.A. L. Goddard, J. Murphy, R.J. Stouffer, G. Boer, G. Danabasoglu, K. Dixon, M.A. Giorgetta, A. Greene, E. Hawkins, G. Hegerl, D. Karoly, N. Keenlyside, M. Kimoto, B. Kirtman, A. Navarra, R. Pulwarty, D. Smith, D. Stammer, and T. Stockdale, 2009: Decadal prediction: Can it be skillful? Bull. Amer. Meteorol. Soc., 90, 14671485.May 30, 2011 13

Koldunov, N., D. Stammer, and J. Marotzke, 2010: Characteristics of present-day Arctic sea ice variability as simulated in MPI-M coupled ocean-ice model runs. J. Clim.,23, 2520-2543.

Romanova, V., A. Köhl, D. Stammer, C. Klepp, A. Andersson and S. Bakan, 2010: Surface freshwater flux estimates from GECCO and HOAPS. Tellus, 62, doi:10.1111/j.1600-0870.2010.00447.x., p. 435-452.

Martinez, N., N. Serra, D. Stammer and P. Minnett, 2010: Response of the eastern sub-tropical Atlantic SST to Saharan Dust: a modeling and observational study. J. of Geophys. Res., 115, C08015, doi:10.1029/2009JC005692.

Romanova, V., A. Köhl, and D. Stammer, 2011: Seasonal Cycle of Near Surface Freshwater Budget in the Western Tropical Atlantic, J. Geophys. Res., in press.

Stammer D., Agarwal N., Herrmann P., Köhl Armin and Mechoso C.R., 2011, Response of a coupled Ocean-Atmosphere Model to Greenland Ice Melting, Surveys in Geophys. In Press.