ENSO and PDO Effect on Stratospheric Dynamics in Isca Numerical Experiments

Atmosphere. 2023. Vol. 14. No. 3. Article 459.

Sobaeva D., Zyulyaeva Y., Gulev S.

The deterministic forecast of the stratospheric polar vortex intensity (iSPV) is limited by 2 weeks, but it can be probabilistically predicted for a longer period due to low-frequency components of the climate system, such as large-scale sea surface temperature anomalies (SSTAs) e.g. El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). For a qualitative and quantitative assessment of the effect of the large-scale Pacific SSTAs on the iSPV anomalies formation, idealized model experiments were carried out using ISCA platform. There is no statistically significant response of the SPV dynamics to the SSTAs corresponding to PDO phases, but they noticeably correct the effect of ENSO modes when added to them. The effect of the El Niño (EN) and La Niña (LN) events with neutral PDO phase on the iSPV is asymmetric, in the “single” EN experiment the vortex is 40% weaker relative to the control values, and in the “single” LN, the SPV is weakened by no more than 20%. When EN accompanied with the positive PDO phase, iSPV is reduced by 58%. When the negative PDO phase is added, the EN effect is significantly weakened. The LN effect is weakened by either positive or negative PDO phase.

Keywords: численное моделирование, стратосферный полярный вихрь, ENSO, PDO, stratosphere-troposphere interaction, tropics-high latitude teleconnection, ЭНЮК, стратосферно-тропосферное взаимодействие