Measurements of the Effects of Gravity Waves in the Middle Atmosphere Using Parametric Models of Density Fluctuations. Part I: Vertical Wavenumber and Temporal Spectra

Sica, R. J.; Russell, Axel

doi:10.1175/1520-0469(1999)056<1308:moteog>2.0.co;2

Cited by 20 publications

(14 citation statements)

References 26 publications

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“…Hence, we discuss the extraction of gravity waves from temperature data rather than atmospheric density, although most of the results can be applied to density measurements as well. For different methods of extracting gravity waves from density measurements see, e.g., Sica and Russell (1999), Thurairajah et al (2010) and Mzé et al (2014).…”

Section: Methodsmentioning

confidence: 99%

Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements

Ehard

Kaifler

et al. 2015

Atmos. Meas. Tech.

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Abstract. This study evaluates commonly used methods of extracting gravity-wave-induced temperature perturbations from lidar measurements. The spectral response of these methods is characterized with the help of a synthetic data set with known temperature perturbations added to a realistic background temperature profile. The simulations are carried out with the background temperature being either constant or varying in time to evaluate the sensitivity to temperature perturbations not caused by gravity waves. The different methods are applied to lidar measurements over New Zealand, and the performance of the algorithms is evaluated. We find that the Butterworth filter performs best if gravity waves over a wide range of periods are to be extracted from lidar temperature measurements. The running mean method gives good results if only gravity waves with short periods are to be analyzed.

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Section: Methodsmentioning

confidence: 99%

Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements

Ehard

Kaifler

et al. 2015

Atmos. Meas. Tech.

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“…Similar filters are used in space or time for spectral analysis of atmospheric waves (e.g., Sica and Russell, 1999). Filter parameters are reported in the data files that are locally produced and distributed to the scientific user community.…”

Section: Review Of Vertical Resolution Definitions Used By Ndacc Lidamentioning

confidence: 99%

Proposed standardized definitions for vertical resolution and uncertainty in the NDACC lidar ozone and temperature algorithms – Part 1: Vertical resolution

et al. 2016

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Abstract.A standardized approach for the definition and reporting of vertical resolution of the ozone and temperature lidar profiles contributing to the Network for the Detection for Atmospheric Composition Change (NDACC) database is proposed. Two standardized definitions homogeneously and unequivocally describing the impact of vertical filtering are recommended.The first proposed definition is based on the width of the response to a finite-impulse-type perturbation. The response is computed by convolving the filter coefficients with an impulse function, namely, a Kronecker delta function for smoothing filters, and a Heaviside step function for derivative filters. Once the response has been computed, the proposed standardized definition of vertical resolution is given by z = δz × H FWHM , where δz is the lidar's sampling resolution and H FWHM is the full width at half maximum (FWHM) of the response, measured in sampling intervals.The second proposed definition relates to digital filtering theory. After applying a Laplace transform to a set of filter coefficients, the filter's gain characterizing the effect of the filter on the signal in the frequency domain is computed, from which the cut-off frequency f C , defined as the frequency at which the gain equals 0.5, is computed. Vertical resolution is then defined by z = δz/(2f C ). Unlike common practice in the field of spectral analysis, a factor 2f C instead of f C is used here to yield vertical resolution values nearly equal to the values obtained with the impulse response definition using the same filter coefficients. When using either of the proposed definitions, unsmoothed signals yield the best possible vertical resolution z = δz (one sampling bin).Numerical tools were developed to support the implementation of these definitions across all NDACC lidar groups. The tools consist of ready-to-use "plug-in" routines written in several programming languages that can be inserted into any lidar data processing software and called each time a filtering operation occurs in the data processing chain.When data processing implies multiple smoothing operations, the filtering information is analytically propagated through the multiple calls to the routines in order for the standardized values of vertical resolution to remain theoretically and numerically exact at the very end of data processing.

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“…The analysis of high resolution radiosonde measurements by Vincent et al [1997] has suggested that the gravity wave field in the lower stratosphere may actually be composed of a mixture of quasi-monochromatic gravity waves and a broad spectrum. Sica and Russell [ 1999] have also shown that intermittent features with narrow bandwidths often tend to dominate the upper straWspheric m spectrum, although a smooth rn'3-type power law exists if sufficient averaging (e.g. hours) is performed.…”

Section: The Problemmentioning

confidence: 99%

How many waves are in the gravity wave spectrum?

Sica¹,

Russell²

1999

Geophysical Research Letters

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Abstract. Parametric modelling of density perturbation measurements obtained with the University of Western Ontario's Purple Crow Lidar on 5 nights are used to infer that the typical vertical wavenumber spectrum in the upper stratosphere is dominated by a few quasi-monochromatic waves. In general only 2 of these waves, with growth or decay rates on the order of 1/(14 km) or less, carry most of the spectral energy. These waves are present about half the time on the nights studied. When analyzed using classical spectral techniques these waves appear to form a continuous spectrum. These results may help explain why general circulation models obtain reasonable climatologies when gravity wave parameterization schemes based on a small number of propagating gravity waves are employed. The ProblemStatistical estimation techniques for the vertical wavenumber spectrum of gravity waves, such as the periodogram or, its equivalent, the correlogram, exhibit a rn 'p power law in the "tail" of the m-spectrum, wherep is typically between 2 and 3 (m is the vertical wavenumber and the tail of the spectrum is defined to be the region of the spectrum between approximately 1/(2500 m) and 1/(100 m)). However, this concept of a smooth spectral form in the tail is now being questioned, especially at high temporal and/or spatial resolution. The analysis of high resolution radiosonde measurements by Vincent et al. [1997] has suggested that the gravity wave field in the lower stratosphere may actually be composed of a mixture of quasi-monochromatic gravity waves and a broad spectrum. Sica and Russell [ 1999] have also shown that intermittent features with narrow bandwidths often tend to dominate the upper straWspheric m spectrum, although a smooth rn'3-type power law exists if sufficient averaging (e.g. hours) is performed.The presence of only a few "dominant" quasi-monochromatic gravity waves in stratospheric m spectra has also been observed in computer simulations. Alexander et al. [1995] have shown that forcing by deep convective processes in squall lines can generate high frequency, narrow bandwidth gravity waves which then propagate into the middle atmosphere with little dispersion. Prusa et al. [1996] have shown tropospheric forcing by Gaussian sources such as topographic features or deep convection can also produce quasi-monochromatic waves in the upper stratosphere and mesosphere through dispersive processes.Characterization of the stratospheric rn spectrum has important implications for constraining gravity wave parameterization schemes used in many global circulation models (GCMs), in part because these parametrizations range from those using a small Prony's method allows individual waves in the spectrum to be estimated from a given data series. In this study the data series are height profries of density perturbations measured by the Purple Crow Lidar's Rayleigh-scatter system [Sica et al. 1995]. A Prony analysis of these density perturbation measurements will then allow us to determine whether or not the spectrum is compris...

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Measurements of the Effects of Gravity Waves in the Middle Atmosphere Using Parametric Models of Density Fluctuations. Part I: Vertical Wavenumber and Temporal Spectra

Cited by 20 publications

References 26 publications

Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements

Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements

Proposed standardized definitions for vertical resolution and uncertainty in the NDACC lidar ozone and temperature algorithms – Part 1: Vertical resolution

How many waves are in the gravity wave spectrum?

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