Impact of the lower thermospheric winter‐to‐summer residual circulation on thermospheric composition

Qian, Liying; Yue, Jia

doi:10.1002/2017gl073361

Cited by 32 publications

(52 citation statements)

References 27 publications

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“…In winter months the simulated meridional wind is the winter‐to‐summer lower thermospheric circulation that is above the summer‐to‐winter mesospheric circulation, driven by the dissipation of upward propagating gravity waves/tides (e.g., Holton, ; Lindzen, ; H.‐L. Liu, ; Qian, Burns, & Yue, ; Qian & Yue, ; Smith et al, ). This winter‐to‐summer wind is evident in Figure c, showing as the negative meridional wind above the summer‐to‐winter positive meridional wind in the Northern Hemisphere (winter hemisphere).…”

Section: Resultsmentioning

confidence: 99%

Trends and Solar Irradiance Effects in the Mesosphere

2019

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We investigate trends and solar irradiance effects in the mesosphere using the Whole Atmosphere Community Climate Model with eXtended thermosphere and ionosphere (WACCM‐X) and radar measurements of winds at Collm (51°N, 13°E), for the period of 1980–2014. We found that in the mesosphere, dynamics significantly impact temperature and wind trends, as well as how solar irradiance affects the temperature and winds. The global average temperature trends are negative, with a maximum of ~−1 K per decade in the middle to lower mesosphere. Solar irradiance effects on the global average temperature are positive and decrease monotonically with decreasing altitude, changing from ~3 K/100 solar flux units (sfu) near the mesopause to ~1 K per 100 sfu in the lower mesosphere. In the summer upper mesosphere, temperature trends can become near 0 or positive, likely due to dynamical effects. Both wind trends and solar effects on the winds show dynamical patterns with negative and positive values, indicating that they are predominantly controlled by dynamics. The wind trends and solar effects on the winds are on the orders of ~±5 m/s per decade and ~±5 m/s per 100 sfu, respectively, and they are not as statistically significant as their temperature counterparts. At Collm (51°N, 13°E), the observed zonal winds at 90 km have a larger trend of 1.98 m/s per decade compared to the simulated zonal winds and it is statistically significant, but both the simulated and observed meridional winds do not have statistically significant trends.

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Section: Resultsmentioning

confidence: 99%

Trends and Solar Irradiance Effects in the Mesosphere

2019

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“…This is done while keeping other species' number densities, temperature, and winds constant at the model lower boundary. This is different from Qian and Yue (2017) because our goal is to explain the mechanisms that are involved in lower‐upper thermospheric coupling in the context of lower thermospheric O concentration rather than the winter‐to‐summer circulation.…”

Section: Introductionmentioning

confidence: 87%

“…In the mesosphere, the meridional circulation is in the same direction, from summer to winter, but driven by a different mechanism. Large westward gravity wave drag in the winter hemisphere, and eastward gravity wave drag in the summer hemisphere causes the circulation to be from summer to winter through Coriolis force (Qian & Yue, 2017). Smith et al (2010) used O mixing ratio at 0.0046 hPa (∼84 km) from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument to show that there is a winter maximum in O which is likely linked to the abovementioned gravity wave driven downwelling in the winter.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Lower Thermospheric Atomic Oxygen on Thermospheric Dynamics and Composition Using the Global Ionosphere Thermosphere Model

et al. 2020

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The exchange of energy between the lower atmosphere and the ionosphere thermosphere system is not well understood. One of the parameters that is important in the lower thermosphere is atomic oxygen. It has recently been observed that atomic oxygen is higher in summer at ∼95 km. In this study, we investigate the sensitivity of the upper thermosphere to lower thermospheric atomic oxygen using the Global Ionosphere Thermosphere Model (GITM). We use the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) to drive the lower atmospheric boundary of atomic oxygen in GITM between ∼95 and 100 km and compare the results with the current mass spectrometer incoherent scatter (MSIS) driven GITM. MSIS has higher atomic oxygen in the winter hemisphere while WACCM-X has higher atomic oxygen in the summer hemisphere. The reversal of atomic oxygen distribution affects the pressure distribution between 100 and 120 km, such that the hemisphere with larger O number density has stronger equatorward winds, and lower temperature mainly due to adiabatic and radiative cooling. This affects thermospheric scale heights such that the hemisphere with more O has lower N 2 and thus enhanced O/N 2. This behavior is observed in the opposite hemisphere when MSIS is used as the lower boundary for GITM. Overall, O/N 2 for WACCM-X driven GITM matches better with the global ultraviolet imager (GUVI) data. We find that the impact of lower thermospheric atomic oxygen on upper thermosphere is not just through diffusive equilibrium but also through secondary effects on winds and temperature.

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“…Other mechanisms, including magnetospheric energy input (Walterscheid, ) and seasonal variations in gravity wave breaking and eddy diffusion (Qian et al, , ), were either found to be too weak or sufficient but not necessary conditions for driving the global AO and SAO in the ionosphere and thermosphere. Qian and Yue () found that the lower thermospheric residual circulation can impact the latitudinal gradient of thermosphere composition and thus can influence the thermospheric AO and SAO. In order to fully understand thermospheric AO and SAO, and the corresponding mechanisms, global observations of thermospheric composition and density profiles are needed.…”

Section: Introductionmentioning

confidence: 99%

Annual and Semiannual Oscillations of Thermospheric Composition in TIMED/GUVI Limb Measurements

et al. 2019

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The Global UltraViolet Imager (GUVI) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite provides a data set of vertical thermospheric composition (O, N 2 , and O 2 densities) and temperature profiles from 2002-2007. Even though GUVI sampling is limited by orbital constraint, we demonstrated that the GUVI data set can be used to derive the altitude profiles of the amplitudes and phases of annual oscillation (AO) and semiannual oscillation (SAO), thereby providing important constraints on models seeking to explain these features. We performed a seasonal and interannual analysis of GUVI limb O, O 2 , and N 2 densities and volume number density ratio O/N 2 at constant pressure levels. These daytime observations of O and O/N 2 in the lower thermosphere show a strong AO at midlatitudes and a clear SAO at lower latitudes. The global mean GUVI O/N 2 number density ratio shows the AO, with slightly larger values in January than in July and a SAO with O/N 2 greater during equinoxes than at the solstices. O and N 2 densities on fixed pressure levels in the upper thermosphere are anticorrelated with solar extreme ultraviolet flux. On the other hand, O/N 2 is smaller during solar minimum and larger during solar maximum. The thermospheric AO and SAO in composition have a constant phase with altitude throughout the thermosphere.

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Impact of the lower thermospheric winter‐to‐summer residual circulation on thermospheric composition

Cited by 32 publications

References 27 publications

Trends and Solar Irradiance Effects in the Mesosphere

Trends and Solar Irradiance Effects in the Mesosphere

Impacts of Lower Thermospheric Atomic Oxygen on Thermospheric Dynamics and Composition Using the Global Ionosphere Thermosphere Model

Annual and Semiannual Oscillations of Thermospheric Composition in TIMED/GUVI Limb Measurements

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