The Impact of the Tropical Sea Surface Temperature Variability on the Dynamical Processes and Ozone Layer in the Arctic Atmosphere

Abstract

Tropical sea surface temperature (SST) variability, mainly driven by the El Niño–Southern Oscillation (ENSO), influences the atmospheric circulation and hence the transport of heat and chemical species in both the troposphere and stratosphere. This paper uses Met Office, ERA5 and MERRA2 reanalysis data to examine the impact of SST variability on the dynamics of the polar stratosphere and ozone layer over the period from 1980 to 2020. Particular attention is paid to studying the differences in the influence of different types of ENSO (East Pacific (EP) and Central Pacific (CP)) for the El Niño and La Niña phases. It is shown that during the CP El Niño, the zonal wind weakens more strongly and changes direction more often than during the EP El Niño, and the CP El Niño leads to a more rapid decay of the polar vortex (PV), an increase in stratospheric air temperature and an increase in the concentration and total column ozone than during EP El Niño. For the CP La Niña, the PV is more stable, which often leads to a significant decrease in Arctic ozone. During EP La Niña, powerful sudden stratospheric warming events are often observed, which lead to the destruction of PV and an increase in column ozone.

Numerical Modeling of Atmospheric Temperature and Stratospheric Ozone Sensitivity to Sea Surface Temperature Variability

“…Moreover, if for the Arctic the transition from the La Niña phase to the El Niño phase leads to a weakening of the polar vortex and an increase in temperature and ozone, then in the Antarctic, the polar vortex intensifies and temperature and ozone decrease in the spring [19][20][21]44]. This may be because the main manifestation of the Southern Oscillation occurs in the second half of the year and the beginning of the next year [42], when the BDC promotes the transfer of heat and mass toward the North Pole [42]. In the Southern Hemisphere, the influence of the Southern Oscillation only takes over the end of the period of formation of ozone anomalies (November-December) [42].…”

“…This may be because the main manifestation of the Southern Oscillation occurs in the second half of the year and the beginning of the next year [42], when the BDC promotes the transfer of heat and mass toward the North Pole [42]. In the Southern Hemisphere, the influence of the Southern Oscillation only takes over the end of the period of formation of ozone anomalies (November-December) [42]. However, the observed difference in the effect in the Northern and Southern Hemispheres may be influenced by other factors that require further study [44,47,48].…”

“…The results of the calculations for scenarios corresponding to the most powerful positive and negative SST anomalies in the tropical Pacific Ocean were particularly highlighted. These were 1983, 1998, and 2016, corresponding to the most powerful phase of El Niño, and 1989Niño, and , 2000Niño, and , and 2011, corresponding to the most powerful phase of La Niña [14,[40][41][42]. For the analysis, differences in the mean values for the El Niño years and La Niña years for SST and atmospheric characteristics were calculated.…”

“…In the early 2000s, the model also reproduced the observed alternations of the periods of ozone increase and decrease quite well, but after 2015, the results of satellite observations and numerical modeling diverged significantly. The influence of the Southern Oscillation in the polar stratosphere is manifested, as a rule, in the next year because the maximum changes in SST corresponding to different phases of the Southern Oscillation occur in the second half of the year [42], preceding the winter-spring period in the Arctic. In the Antarctic, the change in the SST most often occurs after the polar night and does not have time to influence the formation of the polar vortex and can only partially influence its destruction in the process of the final warming or it could manifest itself next year.…”

“…As can be seen, throughout the year over the tropical region, there is an increase in temperature of more than 0.5 • for El Niño (Figure 4b) and a decrease of 0.2-0.5 degrees for La Niña (Figure 4a) at altitudes of the upper troposphere-lower stratosphere, then from winter to autumn in the middle stratosphere a decrease to 0.2 degrees. In autumn, when the Southern Oscillation begins to manifest itself most intensely [42], the maximum increase in temperature in the tropics is observed at altitudes from 20 to 30 km. In polar latitudes (60-90 degrees) in September-November, cooling is observed in the lower stratosphere, and in Antarctica, it is more significant than in the Arctic in La Niña.…”