Potential Predictability of the Silk Road Pattern and the Role of SST as Inferred from Seasonal Hindcast Experiments of a Coupled Climate Model

The Silk Road pattern (SR) is a leading mode of atmospheric circulation over midlatitude Eurasia in boreal summer. Its temporal phase is known to be unpredictable in many models. Previous studies have not reached a clear consensus on the role of sea surface temperature (SST) associated with SR. By c...

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Bibliographic Details
Published in:Journal of climate 2020-11, Vol.33 (22), p.9567-9580
Main Authors: Li, Ronald Kwan Kit, Tam, Chi Yung, Lau, Ngar Cheung, Sohn, Soo Jin, Ahn, Joong Bae
Format: Article
Language:English
Subjects:
Anomalies
Atmospheric circulation
Atmospheric models
Bias
Climate models
Connecting
El Nino
El Nino phenomena
El Nino-Southern Oscillation event
General circulation models
Rossby waves
Sea surface
Sea surface temperature
Sea surface temperature anomalies
Southern Oscillation
Surface temperature
Tropical climate
Wave propagation
Waveguides
Wind
Winds
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Summary:The Silk Road pattern (SR) is a leading mode of atmospheric circulation over midlatitude Eurasia in boreal summer. Its temporal phase is known to be unpredictable in many models. Previous studies have not reached a clear consensus on the role of sea surface temperature (SST) associated with SR. By comparing seasonal hindcasts from the Pusan National University (PNU) coupled general circulation model with reanalysis, we investigate if there are any sources of predictability originating from the SST. It was found that the PNU model cannot predict SR temporally. In fact, SR is associated with El Niño–Southern Oscillation (ENSO) in the model hindcasts, in contrast to reanalysis results in which SR is more associated with North Atlantic SST anomalies. The PNU system, however, shows potential predictability in SR associated with tropical Pacific SST. Bias in stationary Rossby waveguides is proposed as an explanation for the SR–ENSO relationship in hindcast runs. Model upper-level wind bias in the North Atlantic results in a less continuous waveguide connecting the North Atlantic to Asia, and may hinder wave propagations induced by North Atlantic SST to trigger SR. On the other hand, model upper-level wind bias in the subtropical western Pacific may favor westward propagation of zonally elongated waves from the ENSO region to trigger SR. This study implies that the role of SST with regard to SR can be substantially changed depending on the fidelity of model upper-level background winds.
ISSN:0894-8755
1520-0442
DOI:10.1175/JCLI-D-20-0235.1