Understanding the Effects of Polar Mesospheric Clouds on the Environment of the Upper Mesosphere and Lower Thermosphere

Siskind, David E.; Merkel, A. W.; Marsh, Daniel R.; Randall, C. E.; Hervig, Mark E.; Mlynczak, Martin G.; Russell, James M.

doi:10.1029/2018jd028830

Cited by 13 publications

(15 citation statements)

References 60 publications

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“…With the inclusion of SABER H data, MSIS 2.0 provides a more accurate description of hydrogen variability in the MLT than MSISE-00 (see Table 2 and spreadsheet S4) One important aspect of this variability is the reversal from a summer maximum at the mesopause (cf. Siskind et al, 2018) to a winter maximum in the upper thermosphere, commonly referred to as the "winter bulge" (Keating & Prior, 1968). Consistent with the known variability of light species, MSISE-00 does have a winter maximum in the upper thermosphere, but has very little seasonal variation in the MLT region (Qian et al, 2018).…”

Section: Atomic Hydrogenmentioning

confidence: 99%

NRLMSIS 2.0: A Whole‐Atmosphere Empirical Model of Temperature and Neutral Species Densities

Emmert

Drob

Bernath

et al. 2021

Earth and Space Science

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232

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NRLMSIS  2.0 is an empirical atmospheric model that extends from the ground to the exobase and describes the average observed behavior of temperature, 8 species densities, and mass density via a parametric analytic formulation. The model inputs are location, day of year, time of day, solar activity, and geomagnetic activity. NRLMSIS 2.0 is a major, reformulated upgrade of the previous version, NRLMSISE-00. The model now couples thermospheric species densities to the entire column, via an effective mass profile that transitions each species from the fully mixed region below ~70 km altitude to the diffusively separated region above ~200 km. Other changes include the extension of atomic oxygen down to 50 km and the use of geopotential height as the internal vertical coordinate. We assimilated extensive new lower and middle atmosphere temperature, O, and H data, along with global average thermospheric mass density derived from satellite orbits, and we validated the model against independent samples of these data. In the mesosphere and below, residual biases and standard deviations are considerably lower than NRLMSISE-00. The new model is warmer in the upper troposphere and cooler in the stratosphere and mesosphere. In the thermosphere, N2 and O densities are lower in NRLMSIS 2.0; otherwise, the NRLMSISE-00 thermosphere is largely retained. Future advances in thermospheric specification will likely require new in situ mass spectrometer measurements, new techniques for species density measurement between 100 and 200 km, and the reconciliation of systematic biases among thermospheric temperature and composition datasets, including biases attributable to long-term changes.

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Section: Atomic Hydrogenmentioning

confidence: 99%

NRLMSIS 2.0: A Whole‐Atmosphere Empirical Model of Temperature and Neutral Species Densities

Emmert

Drob

Bernath

et al. 2021

Earth and Space Science

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232

166

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“…To validate TIME-GCM simulated light species responses to middle atmospheric variability, we compared our modeling results with SABER atomic hydrogen measurements. SABER H has been compared with models by Qian et al (2018) and Siskind et al (2018), with an emphasis on seasonal and solar cycle variability. Here we look at the shorter-term variation in response to several SSW/MC events during the lifetime of SABER, including January 2006, 2009, and 2013 events, as well as January 2014, in which no SSW/MC occurred.…”

Section: Saber H Datamentioning

confidence: 99%

Coupling From the Middle Atmosphere to the Exobase: Dynamical Disturbance Effects on Light Chemical Species

et al. 2020

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This paper characterizes the impacts of sudden stratospheric warmings (SSWs) and mesospheric coolings (MCs) on the light species distribution (i.e., helium [He], and atomic hydrogen [H]) of the thermosphere using a combined data-modeling approach. Performing a set of numerical experiments with a general circulation model whose middle atmospheric dynamical and thermodynamical fields were constrained using a numerical weather prediction system, we simulate the effects of SSWs and MCs on light chemical species, and via comparisons with two data sets taken from the mesosphere and thermosphere, we quantify the associated variability in light species abundances and mass density. Large depletions in the observed and modeled polar H abundance in the mesosphere and lower thermosphere (MLT) occur with MC onset, as opposed to SSW onset. Depletions in all light thermospheric species at high northern latitudes extend up to the exobase in our model simulations during the January 2013 SSW/MC period, with the largest depletions simulated for the lightest species. Further, our modeling work substantiates the paradigm of increased mixing in the MLT driven by a meridional residual circulation during SSWs resulting from enhanced small-scale gravity wave and migrating semidiurnal tidal forcing; the former being the primary driver and the latter of secondary but notable importance in our model simulations. SSW/MC induced light species variability then gets projected upward into the thermosphere through molecular diffusion. Modeled light species variability during the January 2013 SSW/MC event suggests SSW/MC signatures could be present in the topside ionosphere and plasmasphere. Plain Language Summary Sudden stratospheric warmings (SSWs) and mesospheric coolings (MCs) are episodic polar middle atmospheric (∼12-80 km or ∼7-50 miles altitude) dynamical weather events driven by increased wave forcing from the troposphere. These events are known to have global effects on the meteorology of the upper atmosphere (i.e., the thermosphere and ionosphere). Observational and modeling evidence presented in this study demonstrate that SSWs and MCs in the middle atmosphere act to drive changes in the chemical composition of the upper atmosphere through an intricate series of processes, set in motion by SSW/MC enhancements in lower and middle atmospheric wave forcing. Our results show that SSW/MC driven changes in particularly light species like hydrogen extend well into the transition region between Earth's atmosphere and outer space. This implies that middle atmospheric weather may have an impact on the plasma populations several Earth radii above Earth's surface (∼10,000 miles or more away).

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“…The dynamics and circulation in the MLT are important for global transport of important trace chemical species (Smith et al, 2011;Kvissel et al, 2012), including transporting NO x and meteor smoke into the winter polar stratosphere, which can affect stratospheric ozone and surface climate (Funke et al, 2017;Garcia et al, 2017), whereas the annual formation and depletion of polar mesospheric clouds (PMCs) at the summertime mesopause has an impact on sensitive chemical processes (Thurairajah et al, 2013;Siskind et al, 2018). Neutral winds in the MLT can also have first-order effects on the impacts of space weather in the ionised atmosphere above (Jackson et al, 2019;Sassi et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Radar observations of winds, waves and tides in the mesosphere and lower thermosphere over South Georgia island (54° S, 36° W) and comparison with WACCM simulations

et al. 2022

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Abstract. The mesosphere and lower thermosphere (MLT) is a dynamic layer of the earth's atmosphere. This region marks the interface at which neutral atmosphere dynamics begin to influence the upper atmosphere and ionosphere. However, our understanding of this region and our ability to accurately simulate it in global circulation models (GCMs) is limited by a lack of observations, especially in remote locations. To this end, a meteor radar was deployed from 2016 to 2020 on the remote mountainous island of South Georgia (54∘ S, 36∘ W) in the Southern Ocean. In this study we use these new measurements to characterise the fundamental dynamics of the MLT above South Georgia including large-scale winds, solar tides, planetary waves (PWs), and mesoscale gravity waves (GWs). We first present an improved method for time–height localisation of radar wind measurements and characterise the large-scale MLT winds. We then determine the amplitudes and phases of the diurnal (24 h), semidiurnal (12 h), terdiurnal (8 h), and quardiurnal (6 h) solar tides at this latitude. We find very large amplitudes up to 30 m s−1 for the quasi 2 d PW in summer and, combining our measurements with the meteor SAAMER radar in Argentina, show that the dominant modes of the quasi 5, 10, and 16 d PWs are westward 1 and 2. We investigate and compare wind variance due to both large-scale “resolved” GWs and small-scale “sub-volume” GWs in the MLT and characterise their seasonal cycles. Last, we use our radar observations and satellite temperature observations from the Microwave Limb Sounder to test a climatological simulation of the Whole Atmosphere Community Climate Model (WACCM). We find that WACCM exhibits a summertime mesopause near 80 km altitude that is around 10 K warmer and 10 km lower in altitude than observed. Above 95 km altitude, summertime meridional winds in WACCM reverse to poleward, but this not observed in radar observations in this altitude range. More significantly, we find that wintertime zonal winds between 85 to 105 km altitude are eastward up to 40 m s−1 in radar observations, but in WACCM they are westward up to 20 m s−1. We propose that this large discrepancy may be linked to the impacts of secondary GWs (2GWs) on the residual circulation, which are not included in most global models, including WACCM. These radar measurements can therefore provide vital constraints that can guide the development of GCMs as they extend upwards into this important region of the atmosphere.

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Understanding the Effects of Polar Mesospheric Clouds on the Environment of the Upper Mesosphere and Lower Thermosphere

Cited by 13 publications

References 60 publications

NRLMSIS 2.0: A Whole‐Atmosphere Empirical Model of Temperature and Neutral Species Densities

NRLMSIS 2.0: A Whole‐Atmosphere Empirical Model of Temperature and Neutral Species Densities

Coupling From the Middle Atmosphere to the Exobase: Dynamical Disturbance Effects on Light Chemical Species

Radar observations of winds, waves and tides in the mesosphere and lower thermosphere over South Georgia island (54° S, 36° W) and comparison with WACCM simulations

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