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

Pacific and Manila, Philippine, in a climatologically low SLP region. SLPs at these two
observation sites have a strong negative correlation. NOI reflects the oscillation between the
North Pacific Subtropical High and Tropical Low Pressure Belt. It is roughly the north Pacific
equivalent of the Southern Oscillation Index (SOI), and highly correlated with SOI and the sea
surface temperature anomalies (SSTA) in the tropical Eastern Pacific on the interannual scale.
<strong>The</strong> interdecadal variability of SSTA in Niño 3 (Niño-3) that measures the variability of the
tropical Pacific SSTA, and its relationships with the interdecadal variability of NOI and SOI
were studied by using ICOADS dataset and observations. Niño-3, NOI and SOI experienced
climatic abrupt changes in the mid-1970s. <strong>The</strong> increase of Niño-3 after mid-1970s indicated a
notable basin-wide warming in the Pacific Ocean, while NOI and SOI shifted from positive
phases of the interdecadal variation to the negative phases. <strong>The</strong> abrupt jumps of NOI and SOI
were leading the variation of Niño-3.
In spite of the long-term trend, Niño-3, NOI and SOI shared the same interdecadal-scale
periods dominated by positive and negative values, suggesting substantial climate shifts on a
roughly 12~15-year ‘cycle’. After filtering, the interdecadal variations of NOI and SOI showed
different characteristics. Before mid-1970s, NOI and SOI were weaker and out-phase. After
mid-1970s, they were stronger and in-phase. <strong>The</strong> lag-relation revealed that SOI leaded Niño-3
by about 7 months, and NOI by 10 months, the strongest correlation coefficients were weaker
before mid-1970s. After mid-1970s, SOI leaded Niño-3 by 4 months with stronger correlation,
and the same as NOI. <strong>The</strong> long-term and the interdecadal variations of SOI and NOI may
explain the interdecadal variation of Niño-3.
<strong>The</strong> Unsteadiness of NH Stationary Wave
Speaker: Ning Shi
Ning Shi
NUIST
shining0826@hotmail.com
Wang Panxing
NUIST
In this paper, a concept of stationary wave unsteadiness is presented and elucidated in
terms of the framework of Lorenz circulation decomposition, which illustrates the variability of
zonal wave components of stationary wave relative to the intensity of stationary waves on
monthly weather map. Based on the Lorenz circulation decomposition method, the degree of
unsteadiness for the global (local) stationary wave is defined, and then used to analyze the
stationary wave unsteadiness on the latitude band 30-60N, where the stationary wave intensity
of northern hemisphere 500-mb geopotential height, as is well known, is significantly strong.
<strong>The</strong> following results are obtained: 1) <strong>The</strong> degree of unsteadiness characterizes the
space-time variance of global stationary waves in 30-60N belt, and the location of unsteady
belt advances southward and then retreats northward in the course of seasonal march. Steady
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