Combined Impact of El Niño–Southern Oscillation and Pacific Decadal Oscillation on the Northern Winter Stratosphere

• Published in: Atmosphere 2019-04, Vol.10 (4), p.211
• Main Authors: Rao, Jian, Ren, Rongcai, Xia, Xin, Shi, Chunhua, Guo, Dong
• Format: Article
• Language: English
• Subjects: Anomalies; Climate; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; El Niño-Southern Oscillation (ENSO); Impact analysis; La Nina; Laboratories; North Pacific; northern winter stratosphere; Pacific Decadal Oscillation; Pacific Decadal Oscillation (PDO); Polar vortex; Precipitation; Sea surface; Sea surface temperature; Sea surface temperature anomalies; Southern Oscillation; Stratosphere; Stratospheric polar vortexes; Stratospheric vortices; Surface temperature; Temperature; Time series; Tropical climate; Troposphere; Vortices; Wave propagation; Winter
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos10040211

Using reanalysis and the sea surface temperature (SST) analysis, the combined impact of El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on the northern winter stratosphere is investigated. The warm and weak stratospheric polar vortex response to El Niño simply appears during positive PDO, whereas the cold and strong stratospheric polar vortex response to La Niña is preferable during negative PDO in the reanalysis. Two mechanisms may account for the enhanced stratospheric response when ENSO and PDO are in phase. First, the asymmetries of the intensity and frequency between El Niño and La Niña can be identified for the two PDO phases. Second, the extratropical SST anomalies in the North Pacific may also play a role in the varying extratropical response to ENSO. The North Pacific SST anomalies related to PDO superimpose ENSO SST anomalies when they are in phase but undermine them when they are out of phase. The superimposed North Pacific SST anomalies help to increase SST meridional gradient anomalies between tropical and extratropics, as well as to lock the local height response to ENSO. Therefore, the passages for the upward propagation of waves from the troposphere is more unimpeded when positive PDO is configured with El Niño, and vice versa when negative PDO is configured with La Niña.