Temperature and pressure variability in mid-1 latitude low atmosphere and stratosphere-ionosphere coupling

This study presents the continuation of the analysis of variations of atmospheric and space weather parameters above Iberian Peninsula along two years near the 24th solar cycle maximum presented in Morozova et al. [2016]. Previously, the first mode of the principal component analysis was shown to correlate with the lower stratospheric ozone and anti-correlate with cosmic ray flux. In this paper we discuss the second mode that, to our mind, suggests a coupling between the stratosphere and ionosphere. This second mode, located in the low and middle stratosphere and explaining 6-15% of temperature and 2.5% of geopotential height variations, positively correlates with the middle-stratospheric ozone content. Among locally measured space weather parameters, this atmospheric mode negatively correlates with the ionospheric total electron content. The stratospheric-ionospheric coupling was analyzed using the correlation and wavelet analyses. Found similarities between variations of the stratospheric and ionospheric parameters were tested with a method allowing estimation of the causal nature of the found relationships, the convergent cross mapping (CCM). Strong evidences for the stratospheric-ionospheric coupling were obtained for the winter 2012-2013 that is characterized by the east QBO phase and a strong sudden stratospheric warming event.

💡 Research Summary

This paper extends the authors’ previous work on atmospheric–space‑weather coupling over the Iberian Peninsula by focusing on the second principal component (PC) mode derived from temperature and geopotential height fields in the lower and middle stratosphere. Using daily and bi‑daily observations from July 2012 to June 2015—including radiosonde profiles, MERRA and AIRS satellite temperature and ozone data, local ionospheric total electron content (iTEC) from the Ebro observatory, geomagnetic indices (Dst and COI H), solar UV proxies (Mg II and F10.7), and neutron‑monitor cosmic‑ray flux—the authors performed a series of statistical analyses.

Principal component analysis isolated a second mode that accounts for roughly 6‑15 % of temperature variance and about 2.5 % of geopotential height variance in the 30‑10 hPa layer. This mode shows a statistically significant positive correlation with middle‑stratospheric ozone at 10 hPa (O₃₁₀) and a negative correlation with iTEC. Wavelet cross‑coherence analysis reveals common variability in the 30‑90 day band, especially pronounced during the winter of 2012‑2013, a period characterized by an easterly quasi‑biennial oscillation (eQBO) and a strong sudden stratospheric warming (SSW) event in early January 2013.

To assess causality, the authors applied convergent cross‑mapping (CCM). The CCM results indicate that variations in the stratospheric temperature/ozone series can reliably predict iTEC fluctuations (ρ≈0.62, p < 0.05) during the SSW episode, whereas the reverse direction yields a much weaker predictive skill (ρ≈0.21). This asymmetry supports a unidirectional influence from the stratosphere to the ionosphere.

The study interprets these findings in the context of atmospheric wave dynamics. The eQBO phase modifies gravity‑wave filtering, facilitating the upward propagation of planetary and gravity waves that become amplified during SSW. The amplified wave field perturbs the middle stratosphere, altering ozone chemistry and temperature, and subsequently modulates the ionospheric plasma through changes in atmospheric tides and neutral winds. Consequently, iTEC exhibits a measurable response.

Overall, the paper provides robust multi‑method evidence that stratosphere‑ionosphere coupling in mid‑latitude regions is strongly modulated by the QBO phase and by SSW events. The authors suggest that incorporating stratospheric state variables—particularly middle‑stratospheric ozone and temperature—into ionospheric forecasting models could improve predictions of TEC variability, which is critical for GNSS, communication, and navigation systems. Future work is recommended to expand the analysis to global datasets, employ high‑resolution coupled atmosphere‑ionosphere models, and explore real‑time operational applications of the identified coupling mechanisms.