A time-slice experiment with the ECHAM4 AGCM at high resolution: the impact of horizontal resolution on annual mean climate change |
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| Authors: | W May E Roeckner |
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| Institution: | Danish Meteorological Institute, Lyngbyvej 100, DK-2100 Copenhagen ?, Denmark E-mail: may@dmi.dk, DK
Max-Planck-Institute for Meteorology, Bundesstra?e 55, D-20146 Hamburg, Germany E-mail: roeckner@dkrz.de, DE
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| Abstract: | The climate response to increasing levels of atmospheric greenhouse gases, prescribed according to the International Panel
of Climate Change (IPCC) scenario IS92a, is studied in two model simulations. The reference simulation is a transient response
experiment performed with a medium-resolution (T42) coupled general circulation model of the atmosphere and ocean (ECHAM4/OPYC)
developed at the Max-Planck-Institute for Meteorology. For two 30-year “time slices”, representing the present-day climate
and the future climate at the time of effective CO2 doubling, the annual mean climate states are compared with those obtained from the high-resolution (T106) ECHAM4 model forced
with monthly sea surface temperatures and sea-ice from the coupled model. The large-scale changes in temperature, zonal wind,
sea-level pressure and precipitation are broadly similar. This applies, in particular, to the respective zonal means. In general,
except for precipitation, the responses in the time-slice experiments are slightly weaker than those simulated in the coupled
model due to a smaller effect of the horizontal resolution on the simulations of the future (warmer) period than on the simulations
of the present period. On a regional scale, the impact of horizontal resolution is smaller in the Southern than in the Northern
Hemisphere, where the response differences are caused mainly by changes in the positions of the stationary waves. Although
the precipitation responses are broadly similar, there are few notable exceptions such as a more pronounced maximum over the
equatorial oceans in the T106 experiment but a weaker response over low-latitude land areas. Differences in precipitation
response are found especially in areas with strong topographical control such as South America, for example.
Received: 17 January 2000 / Accepted: 7 July 2000 |
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