Whole Atmosphere Coupling on Intraseasonal and Interseasonal Time Scales: A Potential Source of Increased Predictive Capability

Abstract

Recent advances in developing accurate, physics‐based models of the coupled ionosphere‐thermosphere (CIT) system have now made these models an integral part of next‐generation space weather prediction capabilities. These advances have produced a better understanding of how the CIT is affected by variability in the neutral lower atmosphere. However, the impacts on the CIT of lower atmospheric variability over time scales with characteristic periods longer than ~10 days have received little attention, despite clear evidence of this variability in atmospheric circulation patterns throughout the stratosphere, mesosphere, and lower thermosphere. This review synthesizes the state of knowledge on long‐term variability (>10 days) originating in the lower atmosphere and its impacts on the CIT, highlighting the following critical points and challenges: (a) planetary wave oscillations are likely to couple the lower and upper atmospheres, especially those corresponding to normal modes of the atmosphere, but it remains unclear whether they impact the ionosphere directly via wind‐dynamo coupling, or indirectly via modulation of solar and lunar tides; (b) while fast moving planetary wave oscillations are ubiquitous in the CIT especially during solstices, there is only sporadic evidence that the slowest moving modes are also present in the upper atmosphere; (c) there is abundant evidence of long‐term variations of tidal amplitudes in the CIT, but how and why such variations occur still remain; (d) interseasonal variations associated with major tropospheric and stratospheric variability have been observed, but the physical pathways are still poorly understood.

New Observations of Large‐Scale Waves Coupling With the Ionosphere Made by the GOLD Mission: Quasi‐16‐Day Wave Signatures in the F‐Region OI 135.6‐nm Nightglow During Sudden Stratospheric Warmings

“…Pedatella et al (2016) suggested that an enhanced migrating semidiurnal tide (SW2) during SSW events is able to induce a global‐scale upward circulation and thereby a reduction of zonal mean O/N 2 ratio and electron densities (Liu & Roble, 2002; Oberheide et al, 2020; Shepherd et al, 1999). In addition, the intraseasonal variability (e.g., Sassi et al, 2019; Vergados et al, 2018) in the lower atmosphere could be responsible for the observed 60‐day oscillation in brightness as well. However, the 60‐day periodicity is beyond the scope of the current study.…”

The Latitudinal Variation and Hemispheric Asymmetry of the Ionospheric Lunitidal Signatures in the American Sector During Major Sudden Stratospheric Warming Events

“…Observational and modeling studies have revealed that these perturbations were related to the vertical coupling of various lower‐atmospheric waves, such as planetary waves (Pedatella & Forbes, 2009; Vineeth et al., 2009), solar tides (Fuller‐Rowell et al., 2011; Jin et al., 2012; Pedatella et al., 2014), and lunar tides (Fejer et al., 2010; Forbes & Zhang, 2012; J. Liu et al., 2019; Mo & Zhang, 2018; Pedatella et al., 2014). Two coupling mechanisms have emphasized how the lower‐atmospheric waves couple with the F‐region (H. L. Liu, 2016; Pogoreltsev et al., 2007; Sassi et al., 2019; Takahashi et al., 2007; Yamazaki & Richmond, 2013), namely, modulations on the equatorial fountain effect in the E‐region (Goncharenko, Chan, et al., 2010; Goncharenko, Coster, et al., 2010; Pedatella et al., 2012, 2014), and wave propagation directly up to the F‐region (Goncharenko & Zhang, 2008; Park & Lühr, 2012; Pedatella & Maute, 2015). The relative importance of these two mechanisms is not yet conclusively known, partially due to the restriction that most relevant studies are on the equatorial or low‐latitude regions where both mechanisms are active.…”

Preliminary Evidence of Madden‐Julian Oscillation Effects on Ultrafast Tropical Waves in the Thermosphere

“…Shorter‐period (i.e., 3–15 days) oscillations in the lower thermosphere are also common and are thought to result from the dissipation of upward propagating UFKW (Riggin et al, 1997; Tsutsumi et al, 1996) originating in the lower atmosphere and confined to the tropics. While recent attention has focused primarily on the impact of the lower atmosphere on the thermosphere over shorter (e.g., hours to days) and longer (e.g., >100 days) time scales, the role of lower atmospheric variability on intraseasonal (∼30–90 days) time scales has not been clearly established (e.g., Sassi et al, 2019). The Madden‐Julian Oscillation (MJO) is the dominant form of intraseasonal variability in the tropical atmosphere (Madden & Julian, 1972).…”