Changes in Sea-Level Pressure over South Korea Associated with High-Speed Solar Wind Events

We explore a possibility that the daily sea-level pressure (SLP) over South Korea responds to the high-speed solar wind event. This is of interest in two aspects: First, if there is a statistical association this can be another piece of evidence showing that various meteorological observables indeed respond to variations in the interplanetary environment. Second, this can be a very crucial observational constraint since most models proposed so far are expected to preferentially work in higher latitude regions than the low latitude region studied here. We have examined daily solar wind speed ${\rm V}$, daily SLP difference ${\rm \Delta SLP}$, and daily ${\rm \log(BV^{2})}$ using the superposed epoch analysis in which the key date is set such that the daily solar wind speed exceeds 800 ${\rm kms^{-1}}$. We find that the daily ${\rm \Delta SLP}$ averaged out of 12 events reaches its peak at day +1 and gradually decreases back to its normal level. The amount of positive deviation of ${\rm \Delta SLP}$ is +2.5 hPa. The duration of deviation is a few days. We also find that ${\rm \Delta SLP}$ is well correlated with both the speed of solar wind and ${\rm \log(BV^{2})}$. The obtained linear correlation coefficients and chance probabilities with one-day lag for two cases are $r \simeq 0.81$ with $P> 99.9%$, and $r \simeq 0.84$ with $P> 99.9%$, respectively. We conclude by briefly discussing future direction to pursue.

💡 Research Summary

This paper investigates whether daily sea‑level pressure (SLP) over South Korea responds to high‑speed solar‑wind events, extending the well‑documented solar‑terrestrial coupling observed at high latitudes to a low‑latitude region. Using daily solar‑wind speed (V) and interplanetary magnetic‑field (IMF) data from the NASA OMNIWeb database (1986‑present) and daily SLP records from 76 Korean Meteorological Administration stations (spatially averaged over 63 stations), the authors identified twelve isolated events in which the daily solar‑wind speed exceeded 800 km s⁻¹. Each event was separated by at least 31 days to avoid overlap, making the sample rare (occurrence probability <0.1 %).

The key date (day 0) for each event was defined as the day the wind speed crossed the 800 km s⁻¹ threshold. The authors then performed a superposed‑epoch (composite) analysis, aligning all twelve events at day 0 and averaging the surrounding 5‑day windows. To quantify pressure changes, they defined ΔSLP as the difference between the daily SLP and the mean SLP of the preceding five days (day −5 to −1). This moving‑average baseline reduces long‑term seasonal trends and highlights short‑term deviations.

Results show that the solar‑wind speed peaks sharply at day 0 and decays over the next few days, as expected for high‑speed streams (HSS) or CME‑driven events. The ΔSLP response is delayed: it reaches a maximum positive anomaly of +2.5 hPa on day +1, then gradually returns to baseline over the following 2–3 days. The standard error of the mean ΔSLP is ≈0.3 hPa, and a Student’s t‑test yields a false‑alarm probability <0.1 %, confirming statistical significance.

Correlation analysis was performed with a one‑day lag (ΔSLP on day +1 versus solar‑wind parameters on day 0). The Pearson correlation coefficient between ΔSLP and V is r≈0.81, and between ΔSLP and log(B V²) – a proxy for the solar‑wind energy flux density – is r≈0.84. Both correlations have chance probabilities exceeding 99.9 %, indicating a very strong linear relationship. The authors note that the assumption of independent data points may be violated because geophysical time series are often autocorrelated, suggesting that the true significance could be slightly lower.

Most of the selected events are associated with fast coronal mass ejections (CMEs) rather than recurrent coronal‑hole streams, as indicated by concurrent Forbush decreases (FD) observed in neutron‑monitor data. The authors argue that the magnetic cloud and disturbed geomagnetic conditions accompanying these CMEs can modify the global electric circuit, alter ionospheric currents, and ultimately affect tropospheric pressure even at low latitudes. They propose that the observed SLP response may be a manifestation of this chain of processes.

The paper acknowledges limitations: the small number of events, potential autocorrelation, and the lack of direct measurements of atmospheric electric currents. Future work is suggested to (i) expand the event database, (ii) separate the effects of pure high‑speed streams versus CME‑driven events, (iii) incorporate other meteorological variables (temperature, wind) over a broader region, and (iv) develop coupled magnetosphere‑ionosphere‑atmosphere models that can quantitatively link solar‑wind energy input (log(B V²)) to surface pressure changes.

In conclusion, the study provides the first statistical evidence that high‑speed solar‑wind events and associated IMF energy fluxes can produce measurable, short‑lived increases in sea‑level pressure over South Korea. This finding supports the notion that solar‑terrestrial coupling is not confined to polar or high‑latitude regions and underscores the importance of including space‑weather parameters in climate and weather modeling frameworks.