Abstract
Based on the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) reanalysis data from 1981 to 2020, the climatological features of the vertical components of three-dimensional Eliassen–Palm (EP) wave activity fluxes (WAF) were investigated. The parameter is related to eddy heat flux and is a key indicator of the upward and downward propagation of quasi-stationary planetary-scale waves. Northern Hemisphere data from a 30 km height (or about a 10-hPa level) were used for the analysis. We evaluated the extreme values (daily maxima and minima) of the vertical WAFs, the probability of their recurrences, and their interannual and daily variability observed over the last four decades. The correlation between the upward EP WAF maxima and the 10-hPa stratosphere temperature anomalies were examined. The results show that very close relationships exist between these two parameters with a short time lag, but the initial state of the stratosphere is a key factor in determining the strength of these relationships. Moreover, trends over the last 40 years were evaluated. In this research, we did not find any significant changes in the extreme values of the vertical WAFs. Finally, the dominant spatial patterns of upward and downward extreme WAFs were evaluated. The results show that there are three main regions in the stratosphere where extremely intensive upward and downward WAFs can be observed.
Highlights
The results provide a benchmark for assessing the strength of wave activity fluxes (WAF) extremes, their spatial distribution, and their relationship with the temperature of the middle stratosphere
Anomalies, because WAFs intensify during the winter and the most anomalous values are usually registered during late DJF season (Figure 1a)
This is related to the evolution and activity of planetary waves of tropospheric origin and their accumulative influence on the stratosphere
Summary
When the westerly jet in the stratosphere is not strong enough, planetary scale waves from the troposphere can penetrate into the stratosphere, where they break down and dissipate
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