Overview of the 2009 and 2011 Sayarim Infrasound Calibration Experiments

Fee, David; Waxler, Roger; Assink, Jelle; Gitterman, Yefim; Given, Jeffrey W.; Coyne, John; Mialle, Pierrick; Garcés, Milton; Drob, Douglas P.; Kleinert, D. E.; Hofstetter, Rami; Grenard, Patrick

doi:10.1002/jgrd.50398

Cited by 66 publications

(27 citation statements)

References 57 publications

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“…3d, winds only). Although HWM07 is more like a climatology without any year-to-year variation, some studies use it as representation of mean or background wind fields, even for single case studies, (e.g., Assink et al, 2012;Hedlin and Walker, 2012;Fee et al, 2013). However, HWM07 describes the actual winds inadequately: the zonal wind is too weak in the upper stratosphere (compared to ECMWF) and too strong in the upper mesosphere (compared to lidar), with differences up to 20 m s −1 ; in between, mean zonal wind matches quite well.…”

Section: Comparison To Modelsmentioning

confidence: 99%

Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar

et al. 2017

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Abstract. We present an extensive data set of simultaneous temperature and wind measurements in the Arctic middle atmosphere. It consists of more than 300 h of Doppler Rayleigh lidar observations obtained during three January seasons (2012, 2014, and 2015) and covers the altitude range from 30 km up to about 85 km. The data set reveals large yearto-year variations in monthly mean temperatures and winds, which in 2012 are affected by a sudden stratospheric warming. The temporal evolution of winds and temperatures after that warming are studied over a period of 2 weeks, showing an elevated stratopause and the reformation of the polar vortex. The monthly mean temperatures and winds are compared to data extracted from the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Horizontal Wind Model (HWM07). Lidar and ECMWF data show good agreement of mean zonal and meridional winds below ≈ 55 km altitude, but we also find mean temperature, zonal wind, and meridional wind differences of up to 20 K, 20 m s −1 , and 5 m s −1 , respectively. Differences between lidar observations and HWM07 data are up to 30 m s −1 . From the fluctuations of temperatures and winds within single nights we extract the potential and kinetic gravity wave energy density (GWED) per unit mass. It shows that the kinetic GWED is typically 5 to 10 times larger than the potential GWED, the total GWED increases with altitude with a scale height of ≈ 16 km. Since temporal fluctuations of winds and temperatures are underestimated in ECMWF, the total GWED is underestimated as well by a factor of 3-10 above 50 km altitude. Similarly, we estimate the energy density per unit mass for largescale waves (LWED) from the fluctuations of nightly mean temperatures and winds. The total LWED is roughly constant with altitude. The ratio of kinetic to potential LWED varies with altitude over 2 orders of magnitude. LWEDs from ECMWF data show results similar to the lidar data. From the comparison of GWED and LWED, it follows that largescale waves carry about 2 to 5 times more energy than gravity waves.

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Section: Comparison To Modelsmentioning

confidence: 99%

Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar

et al. 2017

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“…Long-range ground-to-ground infrasound propagation is most efficient in the stratosphere [Fee et al, 2013], as the absorption in this waveguide is relatively small [Sutherland and Bass, 2004]. However, a sufficiently strong stratospheric circumpolar vortex in the direction of propagation is required to trap infrasound in the stratosphere.…”

Section: Passive Acoustic Remote Sensingmentioning

confidence: 99%

Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

et al. 2014

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In this paper, we evaluate vertical wind and temperature profiles that are produced by the European Centre for Medium‐Range Weather Forecasts (ECMWF) atmospheric analysis. The evaluation is carried out on both hemispheres: we make use of stratospheric infrasound arrivals from Mount Etna (37°N) and Mount Yasur (22°S). The near‐continuous, high activity of both volcanoes permits the study of stratospheric propagation along well‐defined paths with a time resolution ranging from hours to multiple years. Infrasound observables are compared to theoretical estimates obtained from acoustic propagation modeling using the ECMWF analysis. While a first‐order agreement is found for both hemispheres, we report on significant discrepancies around some of the equinox periods and other intervals during which the atmosphere is in a state of transition and dynamical oscillations of the atmosphere dominate over the general circulation. We present an inversion study in which we make use of measured trace velocity estimates to estimate first‐order effective sound speed model updates in a Bayesian framework. Deviations from the a priori models around the stratopause up to 10% (≈ 30 m s−1) are estimated. Such updates are in line with the results from comparisons between ECMWF analysis and observations from lidar and microwave Doppler spectroradiometer facilities that were colocated during the course of the 2012–2013 Atmospheric dynamics Research and InfraStructure in Europe (ARISE) measurement campaign.

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“…Further, note that differences between ECMWF and G2S are most significant above 50 km. A similar observation was made by Fee et al [].…”

Section: Propagation Modelingmentioning

confidence: 99%

Bidirectional infrasonic ducts associated with sudden stratospheric warming events

et al. 2014

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In January 2011, the state of the polar vortex in the midlatitudes changed significantly due to a minor sudden stratospheric warming event. As a result, a bidirectional duct for infrasound propagation developed in the middle atmosphere that persisted for 2 weeks. The ducts were due to two zonal wind jets, one between 30 and 50 km and the other around 70 km altitude. In this paper, using microbarom source modeling, a previously unidentified source region in the eastern Mediterranean is identified, besides the more well known microbarom source regions in the Atlantic Ocean. Infrasound data are then presented in which the above mentioned bidirectional duct is observed in microbarom signals recorded at the International Monitoring System station I48TN in Tunisia, from the Mediterranean region to the east and from the Atlantic Ocean to the west. While the frequency bands of the two sources overlap, the Mediterranean signal is coherent up to about 0.6 Hz. This observation is consistent with the microbarom source modeling; the discrepancy in the frequency band is related to differences in the ocean wave spectra for the two basins considered. This work demonstrates the sensitivity of infrasound to stratospheric dynamics and illustrates that the classic paradigm of a unidirectional stratospheric duct for infrasound propagation can be broken during a sudden stratospheric warming event.

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Overview of the 2009 and 2011 Sayarim Infrasound Calibration Experiments

Cited by 66 publications

References 57 publications

Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar

Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar

Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

Bidirectional infrasonic ducts associated with sudden stratospheric warming events

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