Fourth Study Conference on BALTEX Scala Cinema Gudhjem

1
0.8
0.6
0.4
0.2
GO(CLD-M)
ERA40
SMHI
0 100 200 300 400
Time (Julian day)
Figure 3. A comparison between ERA40 (black line) and
SMHI 1 0 x1 0 (blue line) total cloudiness above Eastern
Gotland Basin). Daily means averaged over a 30-years
period.
0.35
0.3
0.25
0.2
0.15
0.1
GO(CLD-STD)
ERA40
SMHI
0 100 200 300 400
Time (Julian day)
Figure 4. A comparison between ERA40 (black line) and
SMHI 1 0 x1 0 (blue line) total cloudiness above Eastern
Gotland Basin). Daily standard deviation averaged over a
30-years period.
5. Baltic Sea modelling
In Figure 5, the modelling of sea ice is examined using the
PROBE-Baltic (Omstedt and Axell, 2003) model forced
with the two different meteorological data sets. The
agreements are good between the two data sets. However
both calculations over estimate ice during mild winters. This
indicates that the two data sets have a bias towards land
influence, which makes Baltic Sea winter conditions over
sea slightly too cold.
- 79 -
Figure 5. Annual maximum ice extent in the Baltic Sea:
A comparison between observed (green line) and
modelled data using ERA40 forcing (black line) and
SMHI 1 0 x1 0 forcing (blue line).
6. Discussion
Several aspects of the two different data sets will be
discussed during the conference. In general there is a good
agreement between the two data sets. The ERA40 data
offer much more variables for investigations compared to
the SMHI 1 0 x1 0 data set. However, the SMHI 1 0 x1 0 data is
continuously up dated and could therefore work as a
complement to ERA40 from 2001 and onwards. The
precipitation data over the Baltic Sea seems, however, too
low in the ERA40 data.
References
Karlsson, K.-G., (2003). A 10 year cloud climatology over
Scandinavia derived from NOAA Advanced Very
High Resolution Radiometer imagery. International
Journal of Climatology, 23, 1023-1044.
Omstedt, A. and L., Axell (2003). Modeling the variations
of salinity and temperature in the large Gulfs of the
Baltic Sea. Continental Shelf Research, 23, 265-294
Rutgersson, A., Bumke, K., Clemens, M., Foltescu, V.,
Lindau, R., Michelson, D., Omstedt , A., (2001).
Precipitation Estimates over the Baltic Sea: Present
State of the Art, Nordic Hydrology, 32(4), 285-314.
Omstedt, A., Meuller, L., and L., Nyberg (1997) Interannual,
seasonal and regional variations of precipitation and
evaporation over the Baltic Sea. Ambio, 26, No. 8, 484-
492.