scholarly journals Microbarom radiation and propagation model assessment using infrasound recordings: a vespagram-based approach

2020 ◽  
Author(s):  
Ekaterina Vorobeva ◽  
Marine De Carlo ◽  
Alexis Le Pichon ◽  
Patrick Joseph Espy ◽  
Sven Peter Näsholm
Keyword(s):  
Atmospheric Model ◽  
Propagation Model ◽  
Model Assessment ◽  
Mean Square ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Northern Norway ◽  
Mean Square Difference ◽  
Back Azimuth ◽  
Azimuth Resolution

Abstract. This study investigates the use of a vespagram-based approach as a tool for multi-directional comparison between simulated microbarom soundscapes and infrasound data recorded at ground-based array stations. Data recorded at the IS37 station in northern Norway during 2014–2019 have been processed to generate vespagrams (velocity spectral analysis) for five frequency bands between 0.1 and 0.6 Hz. The back-azimuth resolution between vespagrams and a microbarom model is harmonized by smoothing the modelled soundscapes along the back-azimuth axis with a kernel corresponding to the frequency-dependent array resolution. An estimate of similarity between the output of a microbarom radiation and propagation model and infrasound observations is then generated based on the image processing approach of mean-square difference. The analysis revealed that vespagrams can monitor seasonal variations in the microbarom azimuth distribution, amplitude, and frequency, as well as changes during sudden stratospheric warming. The vespagram-based approach is computationally inexpensive, can uncover microbarom source variability, and has potential for near-real-time stratospheric diagnostics and atmospheric model assessment.

scholarly journals Benchmarking microbarom radiation and propagation model against infrasound recordings: a vespagram-based approach

2021 ◽  
Vol 39 (3) ◽  
pp. 515-531
Author(s):  
Ekaterina Vorobeva ◽  
Marine De Carlo ◽  
Alexis Le Pichon ◽  
Patrick Joseph Espy ◽  
Sven Peter Näsholm
Keyword(s):  
Atmospheric Model ◽  
Propagation Model ◽  
Model Assessment ◽  
Mean Square ◽  
Sudden Stratospheric Warming ◽  
Azimuthal Distribution ◽  
The Mean ◽  
Mean Square Difference ◽  
Back Azimuth ◽  
Azimuth Resolution

Abstract. This study investigates the use of a vespagram-based approach as a tool for multi-directional comparison between simulated microbarom soundscapes and infrasound data recorded at ground-based array stations. Data recorded at the IS37 station in northern Norway during 2014–2019 have been processed to generate vespagrams (velocity spectral analysis) for five frequency bands between 0.1 and 0.6 Hz. The back azimuth resolution between the vespagram and the microbarom model is harmonized by smoothing the modeled soundscapes along the back azimuth axis with a kernel corresponding to the frequency-dependent array resolution. An estimate of similarity between the output of the microbarom radiation and propagation model and infrasound observations is then generated based on the image-processing approach of the mean square difference. The analysis reveals that vespagrams can monitor seasonal variations in the microbarom azimuthal distribution, amplitude, and frequency, as well as changes during sudden stratospheric warming events. The vespagram-based approach is computationally inexpensive, can uncover microbarom source variability, and has the potential for near-real-time stratospheric diagnostics and atmospheric model assessment.

Vespagram-based approach for microbarom radiation and propagation model assessment using infrasound recordings

2021 ◽  
Author(s):  
Ekaterina Vorobeva ◽  
Marine De Carlo ◽  
Patrick Espy ◽  
Sven Peter Näsholm
Keyword(s):  
Low Cost ◽  
Signal Amplitude ◽  
Atmospheric Model ◽  
Propagation Model ◽  
Time Dependent ◽  
Velocity Spectrum ◽  
Model Assessment ◽  
Model Output ◽  
Mean Square Difference ◽  
Back Azimuth

<p>This study investigates a vespagram-based approach as a tool for multi-direction comparison between simulated microbarom soundscapes and infrasound data recorded at ground-based stations. The used microbarom radiation model takes into consideration both finite ocean-depth and the source radiation dependence on elevation and azimuth angles, while the effects of the atmospheric ducting from the source regions to the station are estimated using a semi-empirical attenuation law. The infrasound data recorded at the IS37 station in northern Norway during 2014-2019 are processed in the framework of the velocity spectrum analysis to generate vespagrams presenting signal power depending on time and back-azimuth direction. The analysis is performed for five frequency bands distributed between 0.1 and 0.6 Hz. The processed infrasound data and the modelled microbarom soundscapes are compared in three different aspects: i) azimuthal distribution of dominating signal, ii) signal amplitude and iii) ability to track atmospheric changes during extreme events such as sudden stratospheric warmings (SSW). The back-azimuth resolution between the vespagrams and the microbarom model output is harmonized by smoothing the modelled soundscapes along the back-azimuth axis with a kernel corresponding to the frequency-dependent array resolution. The time-dependent similarity between the model output and the processed infrasound data is estimated using the image processing approach of mean-square difference. The results reveal good agreement between the model and the infrasound data and demonstrate the ability of vespagrams to monitor the time-dependent microbaroms azimuth distribution, amplitude, and frequency on a seasonal scale, as well as changes during SSWs. The presented vespagram-based approach is computationally low-cost and can uncover microbarom source variability. There is also a potential for near-real-time diagnostics of atmospheric model products and microbarom radiation models, especially when applied to multiple stations, e.g. exploiting the CTBTO International Monitoring System network.</p>

scholarly journals Evaluation of Antarctic Ozone Profiles derived from OMPS-LP by using Balloon-borne Ozonesondes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Edgardo Sepúlveda ◽  
Raul R. Cordero ◽  
Alessandro Damiani ◽  
Sarah Feron ◽  
Jaime Pizarro ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Mean Bias Error ◽  
Bias Error ◽  
Mean Square ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Antarctic Ozone ◽  
The Mean

AbstractPredicting radiative forcing due to Antarctic stratospheric ozone recovery requires detecting changes in the ozone vertical distribution. In this endeavor, the Limb Profiler of the Ozone Mapping and Profiler Suite (OMPS-LP), aboard the Suomi NPP satellite, has played a key role providing ozone profiles over Antarctica since 2011. Here, we compare ozone profiles derived from OMPS-LP data (version 2.5 algorithm) with balloon-borne ozonesondes launched from 8 Antarctic stations over the period 2012–2020. Comparisons focus on the layer from 12.5 to 27.5 km and include ozone profiles retrieved during the Sudden Stratospheric Warming (SSW) event registered in Spring 2019. We found that, over the period December-January–February-March, the root mean square error (RMSE) tends to be larger (about 20%) in the lower stratosphere (12.5–17.5 km) and smaller (about 10%) within higher layers (17.5–27.5 km). During the ozone hole season (September–October–November), RMSE values rise up to 40% within the layer from 12.5 to 22 km. Nevertheless, relative to balloon-borne measurements, the mean bias error of OMPS-derived Antarctic ozone profiles is generally lower than 0.3 ppmv, regardless of the season.

Variability of the North Atlantic response to sudden stratospheric warming events in a simplified atmospheric model

2020 ◽  
Author(s):  
Hilla Afargan-Gerstman ◽  
Bernat Jiménez-Esteve ◽  
Daniela I.V. Domeisen
Keyword(s):  
North Atlantic ◽  
Atmospheric Model ◽  
Negative Phase ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Large Variability ◽  
The North ◽  
The Pacific ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

<p>Sudden stratospheric warming (SSW) events are often followed by a surface impact, most commonly by a negative phase of the North Atlantic Oscillation (NAO). Recent work has emphasized the large variability among the tropospheric response after these events, showing that only about two thirds of the SSWs are dominated by this canonical negative NAO response. In this study, we use an idealized atmospheric model forced with seasonally varying sea surface temperatures to examine the influence of the pre-existing tropospheric conditions on the North Atlantic response to stratospheric forcing. In the model, the negative phase of the NAO is found to be the most common response to SSWs, occurring after ~85% of the SSWs (under climatological SST forcing).  For the remaining ~15% of the SSW events, the response is associated with a positive phase of the NAO. In the search for the origin of the different tropospheric response in the North Atlantic, the role of synoptic wave propagation from the eastern Pacific on the downward response to SSWs is investigated. By systematically varying the strength of the North Pacific circulation, we are able to assess the sensitivity of the downward response to tropospheric variability in the Pacific, and shed light on its contribution to the persistence of the downward impact of SSWs in the idealized model.</p>

scholarly journals Identification of the mechanisms responsible for anomalies in the tropical lower thermosphere/ionosphere caused by the January 2009 sudden stratospheric warming

2019 ◽  
Vol 9 ◽  
pp. A39 ◽  
Author(s):  
Maxim V. Klimenko ◽  
Vladimir V. Klimenko ◽  
Fedor S. Bessarab ◽  
Timofei V. Sukhodolov ◽  
Pavel A. Vasilev ◽  
...  
Keyword(s):  
Electric Field ◽  
Phase Change ◽  
Lower Thermosphere ◽  
Upper Atmosphere ◽  
Electron Content ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Low Latitude ◽  
Plasma Drift ◽  
Solar Tide

We apply the Entire Atmosphere GLobal (EAGLE) model to investigate the upper atmosphere response to the January 2009 sudden stratospheric warming (SSW) event. The model successfully reproduces neutral temperature and total electron content (TEC) observations. Using both model and observational data, we identify a cooling in the tropical lower thermosphere caused by the SSW. This cooling affects the zonal electric field close to the equator, leading to an enhanced vertical plasma drift. We demonstrate that along with a SSW-related wind disturbance, which is the main source to form a dynamo electric field in the ionosphere, perturbations of the ionospheric conductivity also make a significant contribution to the formation of the electric field response to SSW. The post-sunset TEC enhancement and pre-sunrise electron content reduction are revealed as a response to the 2009 SSW. We show that at post-sunset hours the SSW affects low-latitude TEC via a disturbance of the meridional electric field. We also show that the phase change of the semidiurnal migrating solar tide (SW2) in the neutral wind caused by the 2009 SSW at the altitude of the dynamo electric field generation has a crucial importance for the SW2 phase change in the zonal electric field. Such changes lead to the appearance of anomalous diurnal variability of the equatorial electromagnetic plasma drift and subsequent low-latitudinal TEC disturbances in agreement with available observations. Plain Language Summary – Entire Atmosphere GLobal model (EAGLE) interactively calculates the troposphere, stratosphere, mesosphere, thermosphere, and plasmasphere–ionosphere system states and their response to various natural and anthropogenic forcing. In this paper, we study the upper atmosphere response to the major sudden stratospheric warming that occurred in January 2009. Our results agree well with the observed evolution of the neutral temperature in the upper atmosphere and with low-latitude ionospheric disturbances over America. For the first time, we identify an SSW-related cooling in the tropical lower thermosphere that, in turn, could provide additional information for understanding the mechanisms for the generation of electric field disturbances observed at low latitudes. We show that the SSW-related vertical electromagnetic drift due to electric field disturbances is a key mechanism for interpretation of an observed anomalous diurnal development of the equatorial ionization anomaly during the 2009 SSW event. We demonstrate that the link between thermospheric winds and the ionospheric dynamo electric field during the SSW is attained through the modulation of the semidiurnal migrating solar tide.

scholarly journals A Trigonometric Projection Method for Overcoming High Intensity Heart Rate Caused Waveform Deformation in Electrocardiogram Biometrics

2021 ◽  
Author(s):  
Tsu-Wang Shen ◽  
Shan-Chun Chang
Keyword(s):  
Heart Rate ◽  
High Intensity ◽  
Correlation Coefficients ◽  
Calibration Method ◽  
Mean Square ◽  
Biometric Technology ◽  
Overall Performance ◽  
Electrocardiogram Signal ◽  
Mean Square Difference ◽  
Electrocardiogram Ecg

Abstract Purpose Although electrocardiogram (ECG) has been proven as a biometric for human identification, applying biometric technology remains challenging with diverse heart rate circumstances in which high intensity heart rate caused waveform deformation may not be known in advance when ECG templates are registered. Methods A calibration method that calculates the ratio of the length of an unidentified electrocardiogram signal to the length of an electrocardiogram template is proposed in this paper. Next, the R peak is used as an axis anchor point of a trigonometric projection (TP) to attain the displacement value. Finally, the unidentified ECG signal is calibrated according to the generated trigonometric value, which corresponds to the trigonometric projection degree of the ratio and the attained displacement measurement. Results The results reveal that the proposed method provides superior overall performance compared with that of the conventional downsampling method, based on the percentage root mean square difference (PRD), correlation coefficients, and mean square error (MSE). Conclusion The curve fitting equation directly maps from the heart rate levels to the TP degree without prior registration information. The proposed ECG calibration method offers a more robust system against heart rate interference when conducting ECG identification.

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