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Wave estimations using winds from RCA, the Rossby regional climate
model
Barry Broman 1 and Ekaterini.E. Kriezi 2
1 Swedish Meteorological and Hydrological Institute, Rossby Centre, Norrköping, Sweden; Barry.Broman@smhi.se
2 Swedish Meteorological and Hydrological Institute, Göteborg, Sweden; Ekaterini.Kriezi@smhi.se
1. Introduction
Waves have now been used in the projections of the climate.
The model SWAN running with winds from the Rossby
Regional Climate Atmospheric model, (RCA). The first
results of this were presented at the International
Symposium US/EU-Baltic 2008 in Tallinn.
2. Future Wave Climate
Hind casts of waves were made with winds from RCA.
When the results were compared to measurements they were
to low. The reason is that the winds in RCA are too week
due to among other thing averaging over the grid cell. In
order to get better results a method were used to “correct”
the winds by using both winds and gusts. This was a great
improvement but more work is needed. In maps and graphs
the comparisons will be given. Below in figure 1 you se an
example of the climate effect on winds after taking the
difference between a reference period and a future
projection.
Figure 1. example of results with the SWAN model
(significant wave heights ): differences in percentiles
between control period and future projection
3. Future plans
The plan is to use results from a coming coupled run
between RCA, the atmospheric model and RCO the
oceanographic model. These will give both winds and ice
which is needed in order to make estimation of eventually
changing wave climate in the Baltic
References
Booij, N., Ris, R.C., Holthuijsen, L.H., 1999. A thirdgeneration
wave model for coastal regions, 1. Model
description and validation. J. Geophys. Res. 104 (C4),
7649–7666.
Broman B, 2007. Estimation of the wave climate for the
Baltic Sea. Poster, Baltic Science Conference, Rostock
2007.
Broman, B., Hammarklint T., Soomere T., Valdmann A.,
2006, Trends and extremes of wave fields in the northeastern
part of the Baltic Proper"
,OCEANOLOGICA,48,2006 pp 165-184.
Davis F. and Newstein H. 1968. The variation of Gust
Factors with Mean wind Speed and with Height.
Journal of Applied Meteorology, Jume 1968, volume
7, 372-378
Gill G.C. 1969. Comments on “The variation of Gust
Factors with
Mean wind Speed and with Height”. Journal of Applied
Meteorology, Notes and correspondence, february
1969, 167
Grabemann I. and Weisse R. 2007 Climate changes
Impact on Extreme Wave conditions in the Noth Sea:
An Esemble Study. Ocean Dynamics, Submitted
Häggmark L., Ivarsson K-I., Gollvik S. and Olofsson P-O,
2000.
Mesan, an operational mesocale analysis system. Tellus,52
A,2-20
Kjellström E., Bärring L., Gollvik S., Hansson U., Jones
C, Samuelsson P, Rummukainen M., Ullerstig A.,
Willén U. and Wyser K., 2005. A 140-year simulation
European climate with new version of the Rossby
Centre regional atmospheric climate model (RCA3),
SMHI, Reports Meteorology and climatology 108
Jönsson A., Broman B., and Rahm L., 2003. Variations in
the Baltic Sea wave fields. Ocean Engineering,
Volume 30, Issue 1, January 2003, 107-126
Nerheim S. 2008. Growing demands for downscaling of
climate
information – examples from predictions of future sea
levels. US/EUBaltic2008
International Symposium, Tallinn Estonia, 27-29 May
2008
Ris, R. C. 1997: Spectral modelling of wind waves in
coastal areas. PhD Thesis, Delft University of
Technology, Delft, Netherlands.
Räisänsen J, Hansson U, Ullerstig A., Döscher R., Graham
L.P., Jones C., Meier M., Samuelsson R., Willén U.,
2003. GCM driven simulations of recent and future
climate with the Rossby Centre coupled Atmospheric
– Baltic Sea regional climate model RCAO. SMHI,
Reports Meteorology and climatology 101
Van der Westhuysen, A.J., M. Zijlema and J.A. Battjes,
2007.
Nonlinear saturation-based whitecapping dissipation in
SWAN for deep and shallow water. Coastal
Engineering, 54, 151-170.
Ekrietsi E. and Broman B. Past and future wave climate in
the Baltic Sea produced by SWAN model with forcing
from the regional climate model RCA of the Rossby
Centre. US/EU-Baltic 2008, Tallinn may 27 -29 2008.