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1. Atmospheric Gravity Waves: Processes and Parameterization

   https://doi.org/10.1175/JAS-D-23-0210.1  

   Achatz, Ulrich; Alexander, M. Joan; Becker, Erich; Chun, Hye-Yeong; Dörnbrack, Andreas; Holt, Laura; Plougonven, Riwal; Polichtchouk, Inna; Sato, Kaoru; Sheshadri, Aditi; et al (February 2024, Journal of the Atmospheric Sciences)

   Abstract Atmospheric predictability from subseasonal to seasonal time scales and climate variability are both influenced critically by gravity waves (GW). The quality of regional and global numerical models relies on thorough understanding of GW dynamics and its interplay with chemistry, precipitation, clouds, and climate across many scales. For the foreseeable future, GWs and many other relevant processes will remain partly unresolved, and models will continue to rely on parameterizations. Recent model intercomparisons and studies show that present-day GW parameterizations do not accurately represent GW processes. These shortcomings introduce uncertainties, among others, in predicting the effects of climate change on important modes of variability. However, the last decade has produced new data and advances in theoretical and numerical developments that promise to improve the situation. This review gives a survey of these developments, discusses the present status of GW parameterizations, and formulates recommendations on how to proceed from there. 

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2. Misaligned Wind‐Waves Behind Atmospheric Cold Fronts

   https://doi.org/10.1029/2024JC021162  

   Sauvage, C; Seo, H; Barr, BW; Edson, JB; Clayson, CA (September 2024, Journal of Geophysical Research: Oceans)

   Atmospheric fronts embedded in extratropical cyclones are high‐impact weather phenomena, contributing significantly to mid‐latitude winter precipitation. The three vital characteristics of the atmospheric fronts, high wind speeds, abrupt change in wind direction, and rapid translation, force the induced surface waves to be misaligned with winds exclusively behind the cold fronts. The effects of the misaligned waves under atmospheric cold fronts on air‐sea fluxes remain undocumented. Using the multi‐year in situ near‐surface observations and direct covariance flux measurements from the Pioneer Array off the coast of New England, we find that the majority of the passing cold fronts generate misaligned waves behind the cold front. Once generated, the waves remain misaligned, on average, for about 8 hr. The parameterized effect of misaligned waves in a fully coupled model significantly increases the roughness length (185%), drag coefficient (19%), and air‐sea momentum flux (11%). The increased surface drag reduces the wind speeds in the surface layer. The upward turbulent heat flux is weakly decreased by the misaligned waves because of the decrease in temperature and humidity scaling parameters being greater than the increase in friction velocity. The misaligned wave effect is not accurately represented in a commonly used wave‐based bulk flux algorithm. Yet, considering this effect in the current formulation improves the overall accuracy of parameterized momentum flux estimates. The results imply that better representing a directional wind‐wave coupling in the bulk formula of the numerical models may help improve the air‐sea interaction simulations under the passing atmospheric fronts in the mid‐latitudes. 

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3. Preliminary Dual-Satellite Observations of Atmospheric Gravity Waves in Airglow

   https://doi.org/10.3390/atmos10110650  

   Yue, Jia; Perwitasari, Septi; Xu, Shuang; Hozumi, Yuta; Nakamura, Takuji; Sakanoi, Takeshi; Saito, Akinori; Miller, Steven D.; Straka, William; Rong, Pingping (November 2019, Atmosphere)

   Atmospheric gravity waves (AGWs) are among the important energy and momentum transfer mechanisms from the troposphere to the middle and upper atmosphere. Despite their understood importance in governing the structure and dynamics of these regions, mesospheric AGWs remain poorly measured globally, and largely unconstrained in numerical models. Since late 2011, the Suomi National Polar-orbiting Partnership (NPP) Visible/Infrared Imaging Radiometer Suite (VIIRS) day–night band (DNB) has observed global AGWs near the mesopause by virtue of its sensitivity to weak emissions of the OH* Meinel bands. The wave features, detectable at 0.75 km spatial resolution across its 3000 km imagery swath, are often confused by the upwelling emission of city lights and clouds reflecting downwelling nightglow. The Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere (IMAP)/ Visible and near-Infrared Spectral Imager (VISI) O2 band, an independent measure of the AGW structures in nightglow based on the International Space Station (ISS) during 2012–2015, contains much less noise from the lower atmosphere. However, VISI offers much coarser resolution of 14–16 km and a narrower swath width of 600 km. Here, we present preliminary results of comparisons between VIIRS/DNB and VISI observations of AGWs, focusing on several concentric AGW events excited by the thunderstorms over Eastern Asia in August 2013. The comparisons point toward suggested improvements for future spaceborne airglow sensor designs targeting AGWs. 

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4. Multiheight Observations of Atmospheric Gravity Waves at Solar Disk Center

   https://doi.org/10.3847/1538-4357/acd930  

   Vesa, Oana; Jackiewicz, Jason; Reardon, Kevin (July 2023, The Astrophysical Journal)

   Abstract Atmospheric gravity waves (AGWs) are low-frequency, buoyancy-driven waves that are generated by turbulent convection and propagate obliquely throughout the solar atmosphere. Their proposed energy contribution to the lower solar atmosphere and sensitivity to atmospheric parameters (e.g., magnetic fields and radiative damping) highlight their diagnostic potential. We investigate AGWs near a quiet-Sun disk center region using multiwavelength data from the Interferometric Bidimensional Spectrometer and the Solar Dynamics Observatory. These observations showcase the complex wave behavior present in the entire acoustic-gravity wave spectrum. Using Fourier spectral analysis and local helioseismology techniques on simultaneously observed line core Doppler velocity and intensity fluctuations, we study both the vertical and horizontal properties of AGWs. Propagating AGWs with perpendicular group and phase velocities are detected at the expected temporal and spatial scales throughout the lower solar atmosphere. We also find previously unobserved, varied phase difference distributions among our velocity and intensity diagnostic combinations. Time–distance analysis indicates that AGWs travel with an average group speed of 4.5 km s⁻¹, which is only partially described by a simple simulation, suggesting that high-frequency AGWs dominate the signal. Analysis of the median magnetic field (4.2 G) suggests that propagating AGWs are not significantly affected by quiet-Sun photospheric magnetic fields. Our results illustrate the importance of multiheight observations and the necessity of future work to properly characterize this observed behavior. 

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5. Persistent plasma waves in interstellar space detected by Voyager 1

   https://doi.org/10.1038/s41550-021-01363-7  

   Ocker, Stella Koch; Cordes, James M.; Chatterjee, Shami; Gurnett, Donald A.; Kurth, William S.; Spangler, Steven R. (August 2021, Nature Astronomy)