Interannual and interdecadal variations in the North Atlantic Oscillation spatial shift

Abstract

The spatial shift of the North Atlantic Oscillation (NAO) is analyzed by using the Twentieth Century Reanalysis version 2 dataset and identifying NAO action centers directly on winter mean sea-level pressure (SLP) anomaly maps. The spatial shift of the NAO is characterized by four NAO spatial shift indices: the zonal and meridional shifts of the NAO southern and northern action centers. It is found that the zonal and meridional shift trends of the NAO action centers move along a path of southwest-northwest direction. Spectral analysis shows that the four NAO spatial shift indices have periodicity of 2-6 years and the NAO index has periodicity of 2-3 years in terms of high-frequency variations. On a decadal time scale, the NAO spatial shift indices are closely (positively) related to the NAO index, which is in agreement with previous studies of the relationship between the NAO index and the spatial shift of the NAO pattern. However, there is no relationship between the NAO index and the meridional shift of the northern action center on an interannual time scale. The significant relationship between the NAO index and the interannual variability of NAO spatial shift indices is very likely to be associated with synoptic-scale Rossby wave breaking, which generates surface pressure anomalies and thus affects the phase and pattern of the NAO. The correlations of winter westerly winds over 90°W-0° and the NAO index and the NAO spatial shift indices have a '+ -+ -' structure from the Equator to the North Pole. Although there is close correlation between the NAO spatial shift indices and the strength of the zonal winds in the North Atlantic region, the effect of the zonal winds on the NAO spatial shift differs at different latitudes. Hence, the role of the zonal winds is probably a result of the NAO spatial shifts.North Atlantic Oscillation, spatial shift, interannual variation, interdecadal variation, zonal winds

Sunshine duration and its variability in the main ridge of the Karkonosze Mountains in relation to with atmospheric circulation

“…5). The former most probably reflects the rhythm of atmospheric circulation in the North Atlantic (North Atlantic Oscillation), while the latter reflects the impact of ocean circulation associated with the AMO (Atlantic Multidecadal Oscillation) mechanism (Schlesinger and Ramankutty 1994;Enfield et al 2001;Portis et al 2001;Zhang et al 2011). Similar relationships have been identified in the case of multi-annual changes in air temperature in the Karkonosze range (Migała et al 2015).…”

Tree‐ring‐based precipitation reconstruction in the source region of Weihe River, northwest China since AD 1810

“…The 15.9‐year and 18.6‐year quasiperiods of reconstructed precipitation were approximate to the interdecadal changes of NAO (Fu and Zeng, ). In addition, NAO also has interannual periodicities (Zhang et al, ). Wavelet coherence analysis (Figure ) showed that the reconstructed precipitation had some similar cycles as the NAO cycles at interannual and interdecadal time scales.…”

The decadal variability of the tropical Indian Ocean SST–the South Asian High relation: CMIP5 model study

“…Since long time variability is significant in both the Indo-Pacific SST and the SAH (Zhang et al 2000;Du and Xie 2008), the data have been detrended to eliminate the contribution of trends to the statistical results. Unless stated, the detrending is performed on the data of each target period, respectively.…”

“…3, except for JJA SST preceding winter after the late-1970s Qu and Huang 2012;Yang et al 2007;Zhang et al 2000).…”

“…The interannual variability of the SAH is shown to relate to the tropical Indian Ocean (TIO) sea surface temperature (SST) (Zhang et al 2000;Yang et al 2007;Huang et al 2011). On interannual timescale, the TIO basin warms up after the peak of El Niño events through "atmospheric bridge" and oceanic dynamics Klein et al 1999;Xie et al 2002).…”