The tenth IMSC, Beijing, China, 2007 - International Meetings on ...

stationary waves occur in mid-latitude band in winter and subtropical area in summer.
Specifically, these are associated with the major troughs of East Asia, North America and a
weaker Europe trough in winter and a relatively steady subtropical high system in summer. A
high value center for the degree of unsteadiness appears at 35N in spring and 50N in summer,
which might be caused by the interannual variation of stationary waves, particularly variations
in association with the strength and zonal migration of stationary waves. 2) <strong>The</strong> degree of
unsteadiness for the local stationary wave clearly shows a zonal asymmetry. <strong>The</strong> steady
zones are always located in areas controlled by strong troughs or ridges of stationary waves,
whereas the unsteady ones are in the areas where the stationary wave intensity is weak. <strong>The</strong>
degree of unsteadiness for local stationary waves in the subtropics is stronger in winter than in
summer, and the reverse is true in the mid-latitude region. Over the local North American
continent, the degree of unsteadiness is slightly less than 1 in summer, indicating that the
stationary wave in this region is more steady than that over other mid- and high latitude region.
As a contrast, North European is the most unsteady area for stationary wave, as represented
by a high value of degree of unsteadiness locally, both in summer and winter. <strong>The</strong> summertime
distribution of degree of unsteadiness shows a rather complicated structure in overall. 3) From
North <strong>China</strong> to the Northwest Pacific, there is a high value of degree of unsteadiness in
summer, with its center located to the east of Heilongjiang Province, which impacts northern
part of <strong>China</strong> including Northeast <strong>China</strong>, North <strong>China</strong> and Northwest <strong>China</strong>. From the
macroscopic point, it, therefore, can explain why these areas become a vulnerable climate
zone in summer. It is obviously that the degree of unsteadiness is an intrinsic characteristic of
stationary waves, and it can be regarded as being of the same importance as the intensity and
energy-spectrum structure of stationary waves for the study of the general circulation system.
Parallel Sessions:Climate Reconstruction
On the loss or preservation of externally forced climate variability in climate field
reconstructions
Speaker: Caspar M. Ammann
Caspar M. Ammann
NCAR
ammann@ucar.edu
Philippe Naveau
Univ. of Colorado / LSCE
Eugene R. Wahl
Alfred Univ.
Because future climate change will be strongest at regional scales - in particular with
regard to the hydrologic cycle, it is important that we understand how radiative forcing can
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