The dominant North Pacific atmospheric circulation patterns and their relations to Pacific SSTs: historical simulations
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The dominant North Pacific atmospheric circulation patterns and their relations to Pacific SSTs: historical simulations and future projections in the IPCC AR6 models Shangfeng Chen1 · Bin Yu2 · Renguang Wu3 · Wen Chen1 · Linye Song4 Received: 1 May 2020 / Accepted: 9 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The first two leading modes of the North Pacific atmospheric variability, the Aleutian Low (AL) and North Pacific Oscillation (NPO), in boreal winter and their relations to the North American and Eurasian surface temperature, El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Victoria Mode (VM) are explored in 20 coupled climate models which participated in the sixth Assessment Report of the Intergovernmental Panel on Climate Change. The historical simulations of these models can well reproduce spatial structures and amplitudes of the winter AL and NPO, as well as their associations with North American and Eurasian surface air temperatures. The close connections of the winter AL with ENSO and PDO, as well as the linkage between the NPO and VM could also be well simulated. However, most of the models lack the capability in simulating the impact of the winter ENSO on the NPO. This deficiency is mainly attributed to westward shifts of the ENSO-related sea surface temperature and precipitation anomalies in the tropics and ENSO-induced atmospheric teleconnections over the North Pacific in the models. Spread in the ENSO’s amplitude also contributes partly to the diversity of the ENSO–NPO relation among the models. Under the SSP2-RCP4.5 forced climate change projection, projected changes in the amplitudes and centers of the AL and NPO exhibit large uncertainties across the 20 models. The close connections of the AL with ENSO and PDO, and the NPO with VM are still robust in the warming climate. Most models project an increase (a decrease) in the AL–PDO (NPO–VM) relationship. However, there exists a large uncertainty in the projected changes of the AL–ENSO relationship, which is partly attributed to the large divergence in the projected changes of the ENSO’s amplitude among the models. Keywords IPCC-AR6 · Aleutian Low · NPO · ENSO · PDO · Victoria mode · Historical simulation · Climate change projection
1 Introduction
* Shangfeng Chen [email protected] 1
Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
2
Climate Research Division, Environment and Climate Change Canada, Toronto, ON, Canada
3
School of Earth Sciences, Zhejiang University, Hangzhou, China
4
Institute of Urban Meteorology, China Meteorological Administration, Beijing, China
North Pacific atmospheric variations and their close connections with the underlying sea surface temperature (SST) variability provide important sources of predictability for subseasonal-interannual climate predictions over many parts of the world, especially over Eurasia and North America (Namias 1969, 1972; Davis 1976; Vimo
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