Signal analysis of the atmospheric mean 500/1000?hPa temperature north of 55°N between 1949 and 1994 |
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| Authors: | H Paeth A Hense |
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| Institution: | Meteorologisches Institut, Universit?t Bonn, Auf dem Hügel 20, 53121 Bonn, Germany E-mail: hpaeth@uni-bonn.de, DE
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| Abstract: | The lower tropospheric mean temperature 500/1000 hPa is examined in the Northern Hemisphere high-latitude region north of
55°N with regard to a climate change signal due to anthropogenic climate forcing as a supplement to previous studies which
concentrated on near surface temperatures. An observational data set of the German Weather Service is compared with several
model simulations including different scenarios of greenhouse gas and sulfate aerosol forcing derived from the two recent
versions of the coupled climate model in Hamburg, ECHAM-3/LSG and ECHAM-4/OPYC. The signal analysis is based on the optimal fingerprint method, which supplies a detection variable with optimal signal-to-noise ratio. The natural variability measures are derived
from the corresponding long-term control experiments. From 1970 onward, we find high trend pattern analogies between the observational
data and the greenhouse-gas induced model simulations. The fingerprint of this common temperature signal consists of a predominate
warming with maximum over Siberia and a weak cooling over the North Atlantic reaching an estimated significance level of about
1%. A non-optimized approach has also been examined, leading to even closer trend pattern correlations. The additional forcing
by sulfate aerosols decreases the correlation of this climate change simulation with the observations. The natural variability
constitutes about 50% of the conforming trend patterns. The signal-to-noise ratio is best over the oceans while the tropospheric
temperatures over the land masses are contaminated by strong noise. The trend pattern correlations look the same for both
model versions and several ensemble members with different noise realizations.
Received: 4 January 1999 / Accepted: 11 April 2001 |
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