Gan, B., L. Wu, F. Jia, S. Li,
W. Cai, H. Nakamura, M. A. Alexander and A. J. Miller,
2017:
On the response of the Aleutian Low to greenhouse warming
Journal of Climate, 30, 3907-3925.
Abstract.
Past and future changes in the Aleutian Low are investigated by
using observation-based sea level pressure (SLP)
datasets and CMIP5 multi-models. It is found that the
Aleutian Low intensity, measured by the North Pacific Index (NPI), has
significantly strengthened during the 20th century,
with the observed centennial-trend double the
modeled counterpart for the multi-model
average of historical simulations, suggesting compound signals
of anthropogenic warming and natural variability.
As climate warms under the strongest future warming scenario,
the climatological-mean Aleutian Low will continue to
intensify and expand northward, as manifested in the significant
decrease (-1.3 hPa) of multi-model-averaged NPI
which is 1.6 times its unforced internal variability and the
central area of low-pressure (SLP < 999 hPa)
expanded about 7 times that in the 20th century. A
suite of idealized experiments further demonstrate that the deepening of
the Aleutian Low can be driven by an El-Nino-like warming of
the tropical Pacific sea surface temperature (SST), with a reduction
in the climatological-mean zonal SST gradient, which
overshadows the dampening effect of a weakened wintertime
land-ocean thermal contrast on the Aleutian Low change
in a warmer climate. While the projected
deepening of Aleutian Low on multi-model average
is robust, individual model portrayals vary
primarily in magnitude. Inter-model difference in
surface warming amplitude over the Asian continent, which is
found to explain about 31% of variance of the
NPI changes across models, has a greater contribution than
that in the spatial pattern of tropical Pacific
SST warming (which explains about 23%)
to model uncertainty in the projection of Aleutian Low intensity.
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