1. Vertical Transport of Sensible Heat and Meteoric Na by the Complete Temporal Spectrum of Gravity Waves in the MLT Above McMurdo (77.84°S, 166.67°E), Antarctica.
- Author
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Chu, Xinzhao, Gardner, Chester S., Li, Xianxin, and Lin, Cissi Ying‐Tsen
- Subjects
GRAVITY waves ,OCEAN waves ,SHEAR waves ,WAVE energy ,ATMOSPHERIC boundary layer ,TRANSPORT theory - Abstract
We report the first lidar observations of vertical fluxes of sensible heat and meteoric Na from 78 to 110 km in late May 2020 at McMurdo, Antarctica. The measurements include contributions from the complete temporal spectrum of gravity waves and demonstrate that wave‐induced vertical transport associated with atmospheric mixing by non‐breaking gravity waves, Stokes drift imparted by the wave spectrum, and perturbed chemistry of reactive species, can make significant contributions to constituent and heat transport in the mesosphere and lower thermosphere (MLT). The measured sensible heat and Na fluxes exhibit downward peaks at 84 km (−3.0 Kms−1 and −5.5 × 104 cm−2s−1) that are ∼4 km lower than the flux peak altitudes observed at midlatitudes. This is likely caused by the strong downwelling over McMurdo in late May. The Na flux magnitude is double the maximum at midlatitudes, which we believe is related to strong persistent gravity waves in the MLT at McMurdo. To achieve good agreement between the measured Na flux and theory, it was necessary to infer that a large fraction of gravity wave energy was propagating downward, especially between 80 and 95 km where the Na flux and wave dissipation were largest. These downward propagating waves are likely secondary waves generated in‐situ by the dissipation of primary waves that originate from lower altitudes. The sensible heat flux transitions from downward below 90 km to upward from 97 to 106 km. The observations are explained with the fully compressible solutions for polarization relations of primary and secondary gravity waves with λz > 10 km. Plain Language Summary: The upper atmosphere is filled with waves that originate in the lower atmosphere from storm systems and airflow over mountainous terrain, and then propagate upward. These waves play key roles in establishing the composition and temperature structures by mixing the upper atmosphere and by perturbing chemical reactions of important reactive species like atomic oxygen and ozone. By using meteoric sodium (Na) that is injected between 78 and 110 km altitude by the vaporization of cosmic dust, as a tracer, and exciting the Na atoms to fluorescence using a lidar system located at McMurdo Station, Antarctica, we directly measured the vertical transport of heat and Na induced by the full spectrum of waves. A surprising discovery is the positive heat flux in the lower thermosphere (97–106 km), which contradicts conventional thinking but demonstrates the importance of the fully compressible solutions for polarization relations of primary and secondary gravity waves. By comparing the measured Na transport with theory, we also show that many of the waves between 80 and 95 km are propagating downward, which are likely generated in this region when upward propagating waves become unstable and break, much like ocean waves behave when breaking over a shoal. Key Points: We report the first observations of vertical fluxes of sensible heat & Na induced by the complete temporal spectrum of gravity wavesMcMurdo sensible heat and Na fluxes exhibit large downward peaks near 84 km and large upward sensible heat fluxes occur at ∼97–106 kmSensible heat & Na flux measurements support theories and show significant impacts of wave‐induced vertical transport and secondary waves [ABSTRACT FROM AUTHOR]
- Published
- 2022
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