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Observations and model predictions of vertical wavenumber spectra of gravity waves in the troposphere and lower stratosphere over a tropical station
Journal of Atmospheric and Solar-Terrestrial Physics ( IF 1.9 ) Pub Date : 2021-03-06 , DOI: 10.1016/j.jastp.2021.105601
M. Pramitha , K. Kishore Kumar , M. Venkat Ratnam

Vertical wavenumber spectra of gravity wave (GW) perturbations of horizontal wind, temperature and ascent rate of the balloon obtained from 10 years (2007–2017) of high resolution radiosonde measurements in the troposphere and lower stratosphere over a tropical station, Gadanki (13.450 N,79.20 E) are investigated. The vertical wavenumber spectrum of ascent rate perturbations obtained from radiosonde is compared with the vertical wavenumber spectrum of the vertical wind perturbations obtained from collocated VHF radar observations for the first time. The vertical wavenumber spectrum is characterised in terms of its slope and amplitude. The analysis indicates that the spectral slopes of horizontal winds and temperature in the lower stratosphere are consistently close to theory predicted value of −3. However, in the troposphere the spectral slopes are relatively less negative as compared to the lower stratosphere. Most importantly, slopes of vertical wind perturbation spectra are completely different from that of horizontal wind as well as temperature spectra. This is indicative that the spectra of wavenumber and intrinsic frequency are not separable. The spectral slopes and amplitudes are quantitatively compared with those predicted by the linear instability theory (LIT), saturated-cascade theory, and diffusive filtering theory. Observed spectra in the lower stratosphere are agreeing well with LIT and Saturated-Cascade theories. Quantitatively, LIT seems to be better in predicting the spectral amplitudes as compared to other theories. The novelty of the present study lies in employing the vertical wavenumber spectra of the ascent rate perturbations to verify the separability of wavenumber-frequency spectra, which is very important to validate the GW saturation theories.



中文翻译:

热带站对流层和平流层下方重力波垂直波数谱的观测和模型预测。

重力波(GW)扰动的垂直波数谱,由加丹基(Gadanki)热带对流层和低平流层中的对流层和低平流层的高分辨率无线电探空仪测量得到的十年(2007-2017)的气球(温度和上升率)得出(13.45 0  N,79.2 0 E)被调查。将从探空仪获得的上升速率扰动的垂直波数谱与首次从并置的VHF雷达观测获得的垂直风扰动的垂直波数谱进行比较。垂直波数频谱以其斜率和幅度为特征。分析表明,低空平流层中水平风和温度的频谱斜率始终接近理论预测值-3。但是,在对流层中,与较低的平流层相比,光谱斜率相对较小。最重要的是,垂直风扰动谱的斜率与水平风以及温度谱的斜率完全不同。这表明波数和固有频率的频谱不可分离。将光谱的斜率和幅度与线性不稳定性理论(LIT),饱和级联理论和扩散过滤理论所预测的结果进行定量比较。平流层下部的观测光谱与LIT和饱和级联理论非常吻合。从数量上讲,与其他理论相比,LIT在预测光谱幅度方面似乎更好。本研究的新颖之处在于利用上升速率扰动的垂直波数谱来验证波数-频谱的可分离性,这对于验证GW饱和理论非常重要。将光谱的斜率和幅度与线性不稳定性理论(LIT),饱和级联理论和扩散过滤理论所预测的结果进行定量比较。平流层下部的观测光谱与LIT和饱和级联理论非常吻合。从数量上讲,与其他理论相比,LIT在预测光谱幅度方面似乎更好。本研究的新颖之处在于利用上升速率扰动的垂直波数谱来验证波数-频谱的可分离性,这对于验证GW饱和理论非常重要。将光谱的斜率和幅度与线性不稳定性理论(LIT),饱和级联理论和扩散过滤理论所预测的结果进行定量比较。平流层下部的观测光谱与LIT和饱和级联理论非常吻合。从数量上讲,与其他理论相比,LIT在预测光谱幅度方面似乎更好。本研究的新颖之处在于利用上升速率扰动的垂直波数谱来验证波数-频谱的可分离性,这对于验证GW饱和理论非常重要。与其他理论相比,LIT在预测频谱幅度方面似乎更好。本研究的新颖之处在于利用上升速率扰动的垂直波数谱来验证波数-频谱的可分离性,这对于验证GW饱和理论非常重要。与其他理论相比,LIT在预测频谱幅度方面似乎更好。本研究的新颖之处在于利用上升速率扰动的垂直波数谱来验证波数-频谱的可分离性,这对于验证GW饱和理论非常重要。

更新日期:2021-03-10
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