Planetary Wave (PW) Generation in the Thermosphere Driven by the PW‐Modulated Tidal Spectrum

Abstract

The National Center for Atmospheric Research thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) is used to conduct numerical experiments that isolate and elucidate a substantial modification of the quasi-6-day wave (Q6DW) above 110 km due to presence of the planetary wave (PW)-modulated tidal spectrum. A two-stage nonlinear tidal interaction is proposed, and its role in vertical coupling by the Q6DW is quantified. The theory enables calculation of net Q6DW accelerations and heating rates in the height-latitude domain (90-300 km; ±75 • ) due to wave-wave interactions of up to 10 ms −1 day −1 and 8 K day −1 , respectively. The Global-Scale Wave Model (GSMW) is used to demonstrate that these forcings produce Q6DW zonal and meridional wind amplitudes, and temperatures, of order 5-20 ms −1 , 5-15 ms −1 , and 5-10 K, respectively. Notably, Q6DW thermal forcing in the GSWM accounts for near-doubling of the wind magnitudes calculated with momentum forcing alone. The computed values are comparable to the 10-22 ms −1 , 3-12 ms −1 , and 4-12 KQ6DW amplitudes calculated with lower-boundary forcing of the Q6DW also included. The proposed two-stage interaction plausibly impacts other PW wind structures in the dynamo region and thus how PW in general participate in atmosphere-ionosphere coupling.

Quasi‐2‐Day Wave in Low‐Latitude Atmospheric Winds as Viewed From the Ground and Space During January–March, 2020

“…The presence of the SWs in the middle thermosphere is traditionally explained in terms of upward propagation of SWs generated in the MLT (see e.g., Yue et al., 2016, Figure 6). No study to date has considered the possibility of SW in‐situ generation in the lower and middle thermosphere (∼100–250 km) where the migrating tidal winds exist due to thermal forcing by extreme ultraviolet solar radiation, and where the vertically propagating semidiurnal migrating tide maintains large amplitudes (e.g., Forbes, Zhang, & Maute, 2020, Figure 6). Palo et al.…”

Quasi‐10‐Day Wave and Semidiurnal Tide Nonlinear Interactions During the Southern Hemispheric SSW 2019 Observed in the Northern Hemispheric Mesosphere

“…Among these oscillations, the Sun‐synchronous (migrating tide‐like) components are typically explained in terms of SSW modulations of tidal heating (e.g., Goncharenko et al, 2012; Siddiqui et al, 2020) and of propagation conditions (e.g., Jin et al, 2012), whereas the non‐Sun‐synchronous (nonmigrating tide‐like) components are conventionally explained as arising from zonal asymmetries in heating or nonlinear interactions between stationary RWs and migrating tides (e.g., Liu et al, 2010). Nonlinear interactions could also occur between RNMs and tides (e.g., Forbes et al, 2020), generating secondary waves at frequencies slightly below and above the tidal frequencies, termed hereafter as lower and upper sidebands (LSBs and USBs), respectively. LSBs and USBs are often misinterpreted as tides (He & Chau, 2019).…”

“…RW‐like oscillations occur at periods from a few days to a few tens of days, mostly explained as RW normal modes (RNMs, e.g., Forbes, 1995; Madden, 1979). RNMs are westward propagating and occur with wave periods near 2, 6, 10, 16, and 28 days and are often referred to as quasi‐2‐, 6‐, 10‐, 16‐, and 28‐day waves (Q2DW, Q6DW, Q10DW, Q16DW, and Q28DW, e.g., Forbes et al, 2017, 2020; Yamazaki, 2018). Associations between RNMs and SSWs have also been broadly reported, although the underlying mechanisms are still under debate (e.g., Pancheva et al, 2008; Stray et al, 2015).…”

Quasi-10-day wave and semi-diurnal tide nonlinear interactions during the southern hemispheric SSW 2019 observed in the northern hemispheric mesosphere

“…RW-like oscillations occur at periods from a few days to a few tens of days, mostly explained as RW normal modes (RNMs, e.g., Forbes, 1995;Madden, 1979). RNMs are westward propagating and occur with wave periods near 2, 6, 10, 16, and 28 days and are often referred to as quasi-2-, 6-, 10-, 16-, and 28-day waves (Q2DW, Q6DW, Q10DW, Q16DW, and Q28DW, e.g., Forbes et al, , 2020Yamazaki, 2018). Associations between RNMs and SSWs have also been broadly reported, although the underlying mechanisms are still under debate (e.g., Pancheva et al, 2008;Stray et al, 2015).…”

“…Among these oscillations, the Sun-synchronous (migrating tide-like) components are typically explained in terms of SSW modulations of tidal heating (e.g., Goncharenko et al, 2012;Siddiqui et al, 2020) and of propagation conditions (e.g., Jin et al, 2012), whereas the non-Sun-synchronous (nonmigrating tide-like) components are conventionally explained as arising from zonal asymmetries in heating or nonlinear interactions between stationary RWs and migrating tides (e.g., Liu et al, 2010). Nonlinear interactions could also occur between RNMs and tides (e.g., Forbes et al, 2020), generating secondary waves at frequencies slightly below and above the tidal frequencies, termed hereafter as lower and upper sidebands (LSBs and USBs), respectively. LSBs and USBs are often misinterpreted as tides (He & Chau, 2019).…”