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Abstract Local full diurnal coverage of temperature variations across the turbopause (∼90–115 km altitude) is achieved by combining the nocturnal observations of a Sodium (Na) Doppler lidar on the Utah State University (USU) campus (41.7°N, 248.2°E) and NASA Michelson interferometer for global high‐resolution thermospheric imaging (MIGHTI)/Ionospheric connection explorer (ICON) daytime observations made in the same vicinity. In this study, utilizing this hybrid data set during summer 2020 between June 12th and July 15th, we retrieve the temperature signatures of diurnal and semidiurnal tides in this region. The tidal amplitudes of both components have similar vertical variation with increasing altitude: less than 5 K below ∼98 km but increase considerably above, up to 19 K near 104 km. Both experience significant dissipation near turbopause altitudes, down to ∼12 K up to 113 km for the diurnal tide and ∼13 K for the semidiurnal tide near 110 km. In addition, while the semidiurnal tidal behavior is consistent with the theoretical predictions, the diurnal amplitude is considerably larger than what is expected in the turbopause region. The tidal phase profile shows a dominance of tidal components with a long vertical wavelength (longer than 40 km) for the semidiurnal tide. On the other hand, the diurnal tide demonstrates close to an evanescent wave behavior in the turbopause region, which is absent in the model results and Thermosphere ionosphere mesosphere energetics and dynamics (TIMED)/Sounding of the atmosphere using broadband radiometry (SABER) observations.
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This content will become publicly available on July 1, 2026
Evaluating Nudging Techniques in Implementing the Lower Atmosphere Variability Induced by Tides and Gravity Waves Into the TIEGCM
Abstract We implement a nudging module into the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) to identify effective techniques for incorporating global‐scale tides and medium‐scale gravity waves (GWs) that induce ionospheric variability. Nudging the full fields of basic state variables minimizes contamination from spectral aliasing and mode coupling, ensuring the most accurate reproduction of each tidal component. In contrast, nudging solely diurnal tides has substantial spectral leakage into semidiurnal tides, leading to underestimations of their own amplitudes and day‐to‐day variabilities (DTDVs). Nudging both diurnal and semidiurnal tides mitigates such underestimations, establishing a minimal requirement for reproducing tidal dynamics and ionospheric DTDVs. Lower boundary forcing (LBF) causes significant deviations of tidal amplitudes and DTDVs near the boundary, but only a ∼10% underestimation above it. The DTDV of vertical ion drift gradually increases with more wave components incorporated and shows a ∼10% underestimation with LBF. Constraining geopotential height (Z*) is critical in TIEGCM to properly add GWs at lower levels. Model runs withZ* constrained exhibit reduced sensitivity to nudging levels: one‐level nudging and LBF runs show 20%–30% underestimations of TID magnitudes compared to a four‐scale‐height nudging run. Conversely, whenZ* is unavailable and onlyU,V,Tare constrained, one‐level nudging and LBF lead to 80%–90% underestimations of TIDs, with LBF entirely missing wave features. Therefore, multi‐level nudging, especially withZ* unconstrained, is recommended to incorporate GWs. Overall, nudging provides a powerful tool to realistically incorporate observed or simulated waves across medium to global scales into ionosphere‐thermosphere models, offering a data‐driven perspective of variability for lower boundary conditions.
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- PAR ID:
- 10617908
- Publisher / Repository:
- AGU
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 130
- Issue:
- 7
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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