We report the first lidar observations of polar mesospheric clouds (PMCs) and temperatures made w... more We report the first lidar observations of polar mesospheric clouds (PMCs) and temperatures made with an Fe Boltzmann lidar at McMurdo, Antarctica in summer 20102011. Eighty-five hours of PMCs were observed between 21 Dec 2010 and 15 Feb 2011, giving an overall ...
Journal Of Geophysical Research: Atmospheres, Aug 17, 2020
This work presents the first lidar observations of a Quasi‐Biennial Oscillation (QBO) in the inte... more This work presents the first lidar observations of a Quasi‐Biennial Oscillation (QBO) in the interannual variations of stratospheric gravity wave potential energy density (Epm in 30–50 km) at McMurdo (77.84°S, 166.67°E), Antarctica. This paper also reports the first identification of QBO signals in the distance between McMurdo and the polar vortex edge. Midwinter stratospheric gravity wave activity is stronger during the QBO easterly phase when the June polar vortex expands and the polar night jet shifts equatorward. During the QBO westerly phase, gravity wave activity is weaker when the polar vortex contracts and the polar night jet moves poleward. Nine years of lidar data (2011–2019) exhibit the mean Epm winter maxima being ~43% higher during QBO easterly than westerly. The June polar vortex edge at 45 km altitude moves equatorward/poleward during QBO easterly/westerly phases with ~8° latitude differences (39.7°S vs. 47.7°S) as revealed in 21 years of MERRA‐2 data (1999–2019). We hypothesize that an equatorward shifted polar vortex corresponds to less critical level filtering of gravity waves and thus higher Epm at McMurdo. The critical level filtering is characterized by wind rotation angle (WRA), and we find a linear correlation between the WRA and Epm interannual variations. The results suggest that the QBO is likely controlling the interannual variations of the Epm winter maxima over McMurdo via the critical level filtering. This observationally based study lays the groundwork for a rigorous numerical study that will provide robust statistics to better understand the mechanisms that link the tropical QBO to extratropical waves.
Journal of Geophysical Research: Space Physics, 2020
A dramatic thermospheric temperature enhancement and inversion layer (TTEIL) was observed by the ... more A dramatic thermospheric temperature enhancement and inversion layer (TTEIL) was observed by the Fe Boltzmann lidar at McMurdo, Antarctica during a geomagnetic storm (Chu et al. 2011, https://doi.org/10.1029/2011GL050016). The Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) driven by empirical auroral precipitation and background electric fields cannot adequately reproduce the TTEIL. We incorporate the Defense Meteorological Satellite Program (DMSP)/Special Sensor Ultraviolet Spectrographic Imager (SSUSI) auroral precipitation maps, which capture the regional‐scale features into TIEGCM and add subgrid electric field variability in the regions with strong auroral activity. These modifications enable the simulation of neutral temperatures closer to lidar observations and neutral densities closer to GRACE satellite observations (~475 km). The regional scale auroral precipitation and electric field variabilities are both needed to generate strong Joule heating that peaks around 120 km. The resulting temperature increase leads to the change of pressure gradients, thus inducing a horizontal divergence of air flow and large upward winds that increase with altitude. Associated with the upwelling wind is the adiabatic cooling gradually increasing with altitude and peaking at ~200 km. The intense Joule heating around 120 km and strong cooling above result in differential heating that produces a sharp TTEIL. However, vertical heat advection broadens the TTEIL and raises the temperature peak from ~120 to ~150 km, causing simulations deviating from observations. Strong local Joule heating also excites traveling atmospheric disturbances that carry the TTEIL signatures to other regions. Our study suggests the importance of including fine‐structure auroral precipitation and subgrid electric field variability in the modeling of storm‐time ionosphere‐thermosphere responses.
Based on two and half years of lidar observations made by the British Antarctic Survey and the Un... more Based on two and half years of lidar observations made by the British Antarctic Survey and the University of Illinois at Rothera (67.5S, 68.0W), Antarctica with an Fe Boltzmann temperature lidar, a systematic analysis was made to characterize the mesospheric Fe layers at this high southern latitude. Rothera Fe layer characteristics are then compared to the South Pole results reported
ABSTRACT In a recently published paper, Friedman and Chu (2007 JGR, doi:10.1029/2006JD008220) pre... more ABSTRACT In a recently published paper, Friedman and Chu (2007 JGR, doi:10.1029/2006JD008220) presented the nocturnal climatology for the mesopause region over Arecibo Observatory (18.35°N, 66.75°W). Continuing this study, we have brought in the sampling effects of the nocturnal-only observations by looking at tidal amplitudes and phases as measured by the TIMED SABER instrument. In this presentation, we discuss the implications of combining the SABER measurements with the nocturnal lidar measurements. We will present the initial results of diurnal lidar temperature measurements from Arecibo, with the long-term goal of fully resolving the thermal structure and making extensive comparisons with SABER measurements.
We report the first lidar observations of polar mesospheric clouds (PMCs) and temperatures made w... more We report the first lidar observations of polar mesospheric clouds (PMCs) and temperatures made with an Fe Boltzmann lidar at McMurdo, Antarctica in summer 20102011. Eighty-five hours of PMCs were observed between 21 Dec 2010 and 15 Feb 2011, giving an overall ...
Journal Of Geophysical Research: Atmospheres, Aug 17, 2020
This work presents the first lidar observations of a Quasi‐Biennial Oscillation (QBO) in the inte... more This work presents the first lidar observations of a Quasi‐Biennial Oscillation (QBO) in the interannual variations of stratospheric gravity wave potential energy density (Epm in 30–50 km) at McMurdo (77.84°S, 166.67°E), Antarctica. This paper also reports the first identification of QBO signals in the distance between McMurdo and the polar vortex edge. Midwinter stratospheric gravity wave activity is stronger during the QBO easterly phase when the June polar vortex expands and the polar night jet shifts equatorward. During the QBO westerly phase, gravity wave activity is weaker when the polar vortex contracts and the polar night jet moves poleward. Nine years of lidar data (2011–2019) exhibit the mean Epm winter maxima being ~43% higher during QBO easterly than westerly. The June polar vortex edge at 45 km altitude moves equatorward/poleward during QBO easterly/westerly phases with ~8° latitude differences (39.7°S vs. 47.7°S) as revealed in 21 years of MERRA‐2 data (1999–2019). We hypothesize that an equatorward shifted polar vortex corresponds to less critical level filtering of gravity waves and thus higher Epm at McMurdo. The critical level filtering is characterized by wind rotation angle (WRA), and we find a linear correlation between the WRA and Epm interannual variations. The results suggest that the QBO is likely controlling the interannual variations of the Epm winter maxima over McMurdo via the critical level filtering. This observationally based study lays the groundwork for a rigorous numerical study that will provide robust statistics to better understand the mechanisms that link the tropical QBO to extratropical waves.
Journal of Geophysical Research: Space Physics, 2020
A dramatic thermospheric temperature enhancement and inversion layer (TTEIL) was observed by the ... more A dramatic thermospheric temperature enhancement and inversion layer (TTEIL) was observed by the Fe Boltzmann lidar at McMurdo, Antarctica during a geomagnetic storm (Chu et al. 2011, https://doi.org/10.1029/2011GL050016). The Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) driven by empirical auroral precipitation and background electric fields cannot adequately reproduce the TTEIL. We incorporate the Defense Meteorological Satellite Program (DMSP)/Special Sensor Ultraviolet Spectrographic Imager (SSUSI) auroral precipitation maps, which capture the regional‐scale features into TIEGCM and add subgrid electric field variability in the regions with strong auroral activity. These modifications enable the simulation of neutral temperatures closer to lidar observations and neutral densities closer to GRACE satellite observations (~475 km). The regional scale auroral precipitation and electric field variabilities are both needed to generate strong Joule heating that peaks around 120 km. The resulting temperature increase leads to the change of pressure gradients, thus inducing a horizontal divergence of air flow and large upward winds that increase with altitude. Associated with the upwelling wind is the adiabatic cooling gradually increasing with altitude and peaking at ~200 km. The intense Joule heating around 120 km and strong cooling above result in differential heating that produces a sharp TTEIL. However, vertical heat advection broadens the TTEIL and raises the temperature peak from ~120 to ~150 km, causing simulations deviating from observations. Strong local Joule heating also excites traveling atmospheric disturbances that carry the TTEIL signatures to other regions. Our study suggests the importance of including fine‐structure auroral precipitation and subgrid electric field variability in the modeling of storm‐time ionosphere‐thermosphere responses.
Based on two and half years of lidar observations made by the British Antarctic Survey and the Un... more Based on two and half years of lidar observations made by the British Antarctic Survey and the University of Illinois at Rothera (67.5S, 68.0W), Antarctica with an Fe Boltzmann temperature lidar, a systematic analysis was made to characterize the mesospheric Fe layers at this high southern latitude. Rothera Fe layer characteristics are then compared to the South Pole results reported
ABSTRACT In a recently published paper, Friedman and Chu (2007 JGR, doi:10.1029/2006JD008220) pre... more ABSTRACT In a recently published paper, Friedman and Chu (2007 JGR, doi:10.1029/2006JD008220) presented the nocturnal climatology for the mesopause region over Arecibo Observatory (18.35°N, 66.75°W). Continuing this study, we have brought in the sampling effects of the nocturnal-only observations by looking at tidal amplitudes and phases as measured by the TIMED SABER instrument. In this presentation, we discuss the implications of combining the SABER measurements with the nocturnal lidar measurements. We will present the initial results of diurnal lidar temperature measurements from Arecibo, with the long-term goal of fully resolving the thermal structure and making extensive comparisons with SABER measurements.
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