From Antarctica Lidar Discoveries to Oasis Exploration

Chu, Xinzhao; Yu, Zhibin; Fong, W.; Chen, Cao; Zhao, Jian; Barry, Ian F.; Smith, John A.; Lu, Xian; Huang, Wentao; Gardner, Chester S.

doi:10.1051/epjconf/201611912001

Cited by 10 publications

(16 citation statements)

References 10 publications

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“…Guided with the latest understandings gained from recent work by Chu et al . [, ] and Yu and Chu [], we propose the following explanation for the formation of thermospheric neutral metal layers over Lijiang. Three major steps are involved according to Yu and Chu [] and Chu et al .…”

Section: Discussionmentioning

confidence: 97%

“…Three major steps are involved according to Yu and Chu [] and Chu et al . []: (1) the transport of metallic ions and electrons from their main deposition regions below 120 km to the E and F regions; (2) convergence of these metallic ions, e.g., by wind shear mechanisms, to form dense ion layers in the thermosphere; and (3) neutralization of the metallic ions (Fe + , Na + , and K + ) through direct electron‐ion recombination to form neutral metal layers (Fe, Na, and K). The polar electric field provides the necessary upward transport of ions in the polar region as modeled by Yu and Chu [], while the equatorial fountain effect plays a vital role in transporting ions at low latitudes as modeled by e.g., Carter and Forbes [] and Bishop and Earle [].…”

Section: Discussionmentioning

confidence: 99%

“…[] observed Fe layers to at least 140 km at Davis (69°S, 78°E), Antarctica. Continuous Fe lidar observations at McMurdo have revealed thermospheric Fe layers exceeding 170 km [ Chu et al ., , ]. Using these layers as tracers, Chu et al .…”

Section: Introductionmentioning

confidence: 99%

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Lidar observations of thermospheric Na layers up to 170 km with a descending tidal phase at Lijiang (26.7°N, 100.0°E), China

et al. 2015

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We report the first lidar observations of thermospheric Na layers up to 170 km at Lijiang (geomagnetic 21.6°N, 171.8°E), China, in March, April, and December 2012. The Na densities inside the layers are low, ranging from ~1 to ~6 cm−3 at altitudes of 130–170 km, about 3 orders of magnitude lower than the Na peak density in the mesopause region. All of these layers exhibit an apparent downward phase progression with a descending rate of 11–12 km/h or ~3 m/s, consistent with the vertical phase speed of semidiurnal tides around 140 km. We have identified at least 12 events from the total 37 nights of lidar observations with four shown in this report, giving an occurrence frequency of ~33% over Lijiang. These thermospheric layer events correspond to strong to moderate equatorial fountain effects, bolstering our hypothesis that the deposit of metallic ions from the equatorial region to low latitudes via the fountain effect provides the Na+ ions in the thermosphere over Lijiang. Adopting the theory by Chu et al. (2011) and the hypothesis by Tsuda et al. (2015), we further hypothesize that the thermospheric Na layers are formed through the neutralization of the tidal‐wind‐shear‐converged Na+ layers via direct electron‐Na+ recombination Na+ + e− → Na + hν. An envelope calculation using reasonable ion and electron densities shows good consistency with the observations.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

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Lidar observations of thermospheric Na layers up to 170 km with a descending tidal phase at Lijiang (26.7°N, 100.0°E), China

et al. 2015

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“…A lidar observational campaign has been ongoing at Arrival Heights observatory (77.84°S, 166.69°E) near McMurdo, Antarctica, since December 2010 via the collaboration between the United States Antarctic Program and Antarctica New Zealand (Chu, Huang, et al, ; Chu, Yu, et al, ). An Fe Boltzmann temperature lidar (Chu et al, ; Wang et al, ) deployed by the University of Colorado Boulder has been recording multiple parameters of the atmosphere from ~15 km to nearly 200 km (e.g., Chen et al, , ; Chen & Chu, ; Chu et al, , ; Chu & Yu, ; Chu et al, ; Fong et al, , ; Lu et al, , , ; Yu et al, ; Zhao et al, ). Analyzed here are the 5 years of lidar temperature data from the pure Rayleigh scattering region (~30–70 km) from 1 January 2011 to 31 December 2015.…”

Section: Methodsmentioning

confidence: 99%

Lidar Observations of Stratospheric Gravity Waves From 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 2. Potential Energy Densities, Lognormal Distributions, and Seasonal Variations

Chu

Zhao

et al. 2018

JGR Atmospheres

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Five years of Fe Boltzmann lidar's Rayleigh temperature data from 2011 to 2015 at McMurdo are used to characterize gravity wave potential energy mass density (Epm), potential energy volume density (Epv), vertical wave number spectra, and static stability N2 in the stratosphere 30–50 km. Epm (Epv) profiles increase (decrease) with altitude, and the scale heights of Epv indicate stronger wave dissipation in winter than in summer. Altitude mean Etrue¯pm and Etrue¯pv obey lognormal distributions and possess narrowly clustered small values in summer but widely spread large values in winter. Etrue¯pm and Etrue¯pv vary significantly from observation to observation but exhibit repeated seasonal patterns with summer minima and winter maxima. The winter maxima in 2012 and 2015 are higher than in other years, indicating interannual variations. Altitude mean trueN2¯ varies by ~30–40% from the midwinter maxima to minima around October and exhibits a nearly bimodal distribution. Monthly mean vertical wave number power spectral density for vertical wavelengths of 5–20 km increases from summer to winter. Using Modern Era Retrospective Analysis for Research and Applications version 2 data, we find that large values of Etrue¯pm during wintertime occur when McMurdo is well inside the polar vortex. Monthly mean Etrue¯pm are anticorrelated with wind rotation angles but positively correlated with wind speeds at 3 and 30 km. Corresponding correlation coefficients are −0.62, +0.87, and +0.80, respectively. Results indicate that the summer‐winter asymmetry of Etrue¯pm is mainly caused by critical level filtering that dissipates most gravity waves in summer. Etrue¯pm variations in winter are mainly due to variations of gravity wave generation in the troposphere and stratosphere and Doppler shifting by the mean stratospheric winds.

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“…The University of Colorado lidar group deployed an Fe Boltzmann temperature lidar [ Chu et al ., ; Wang et al ., ] to Arrival Heights observatory near McMurdo in late 2010 [ Chu et al ., ]. Ever since, the observational campaign has been ongoing for over 5 years, recording multiple parameters of the atmosphere from ~15 km to nearly 200 km, whenever weather permits [ Chu et al ., , , ]. Benefited from this long‐lasting campaign, invaluable data sets were recorded for unraveling mysteries in the Antarctic atmosphere.…”

Section: Methodsmentioning

confidence: 99%

Lidar observations of stratospheric gravity waves from 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 1. Vertical wavelengths, periods, and frequency and vertical wave number spectra

et al. 2017

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Five years of atmospheric temperature data, collected with an Fe Boltzmann lidar by the University of Colorado group from 2011 to 2015 at Arrival Heights, are used to characterize the vertical wavelengths, periods, vertical phase speeds, frequency spectra, and vertical wave number spectra of stratospheric gravity waves from 30 to 50 km altitudes. Over 1000 dominant gravity wave events are identified from the data. The seasonal spectral distributions of vertical wavelengths, periods, and vertical phase speeds in summer, winter, and spring/fall are found obeying a lognormal distribution. Both the downward and upward phase progression gravity waves are observed by the lidar, and the fractions of gravity waves with downward phase progression increase from summer ~59% to winter ~70%. The seasonal and monthly mean vertical wavelengths and periods exhibit clear seasonal cycles with vertical wavelength growing from summer ~5.5 km to winter ~8.5 km, and period increasing from summer ~4.5 h to winter ~6 h. Statistically significant linear correlations are found between the monthly mean vertical wavelengths/periods and the mean zonal wind velocities from 30 to 50 km. Assuming horizontal phase speeds independent of month, the monthly mean horizontal wavelengths, intrinsic periods, and group velocities are estimated for stratospheric gravity waves. The slopes of wave frequency spectra change from −1.9 at 30–60 km to −1.45 around 60–65 km. The vertical wave number spectra show the power spectral density at vertical wavelengths of 5–20 km decreasing from winter maximum to summer minimum. Several aforementioned features are observed for the first time in Antarctica.

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From Antarctica Lidar Discoveries to Oasis Exploration

Cited by 10 publications

References 10 publications

Lidar observations of thermospheric Na layers up to 170 km with a descending tidal phase at Lijiang (26.7°N, 100.0°E), China

Lidar observations of thermospheric Na layers up to 170 km with a descending tidal phase at Lijiang (26.7°N, 100.0°E), China

Lidar Observations of Stratospheric Gravity Waves From 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 2. Potential Energy Densities, Lognormal Distributions, and Seasonal Variations

Lidar observations of stratospheric gravity waves from 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 1. Vertical wavelengths, periods, and frequency and vertical wave number spectra

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