Measuring Gravity Wave Parameters from a Nighttime Satellite Low-Light Image Based on Two-Dimensional Stockwell Transform

Hu, Shensen; Ma, Shuo; Yan, Wei; Hindley, Neil P.; Xu, Kaidong; Jiang, Jun

doi:10.1175/jtech-d-18-0092.1

Cited by 9 publications

(3 citation statements)

References 32 publications

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“…Based upon Stockwell et al (1996), this provides estimates of the dominant wave amplitudes, wavelengths and directions at every location in a 3-D data volume. This method has been applied to 3-D AIRS data and other geophysical data sets in several recent studies (Hindley et al, 2016(Hindley et al, , 2019Hu, Ma, Yan, Hindley, Xu, & Jiang, 2019;Hu, Ma, Yan, Hindley, & Zhao, 2019;Wright et al, 2017).…”

Section: Measuring 3-d Gw Propertiesmentioning

confidence: 99%

An 18‐Year Climatology of Directional Stratospheric Gravity Wave Momentum Flux From 3‐D Satellite Observations

Hindley

Wright

Hoffmann

et al. 2020

Geophysical Research Letters

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Atmospheric gravity waves (GWs) are key drivers of the atmospheric circulation, but their representation in general circulation models (GCMs) is challenging, leading to significant biases in middle atmospheric circulations. Unresolved GW momentum transport in GCMs must be parameterized, but global directional GW observations are needed to constrain this. Here we present an 18-year climatology of directional stratospheric GW momentum flux (GWMF) from global AIRS/Aqua 3-D satellite observations during 2002 to 2019. Striking hemispheric asymmetries are found at high latitudes, including dramatic reductions and reversals of GWMF during sudden stratospheric warmings. During Southern Hemisphere winter, a lateral convergence of GWMF toward 60°S is found that has no Northern Hemisphere counterpart. In the tropics, we find that zonal GWMF in AIRS measurements is strongly modulated by the semiannual oscillation (SAO) but not the quasi-biennial oscillation (QBO). Our results provide guidance for future GW parameterizations needed to resolve long-standing biases in GCMs. Plain Language Summary Gravity waves (GWs) are traveling waves that can occur in geophysical fluid environments subject to the gravitational force. In the Earth's atmosphere, GWs transport momentum that helps to drive the atmospheric circulation, especially in the middle atmosphere. But for numerical weather and climate models, accurately simulating GWs has proven very challenging because of a lack of GW observations, leading to significant model biases. Here we present an 18-year climatology of GW observations near 40-km altitude for 2002 to 2019. For the first time, we present multidecadal global measurements of directional GW momentum flux derived from 3-D satellite observations from National Aeronautics and Space Administration's (NASA's) AIRS instrument. We find that during Southern Hemisphere winter, GWs travel laterally toward 60°S each year. This is significant because most models underestimate GW momentum near 60°S and do not typically include lateral propagation in their parameterizations. In the tropical stratosphere, we find no modulation of GWs in AIRS observations by the quasi-biennial oscillation (QBO). This is consistent with the hypothesis that GW-QBO interactions occur at shorter vertical wavelengths, which are invisible to AIRS. Our results will help to guide future GW parameterizations, leading to more accurate atmospheric simulations and ultimately better forecasts of weather and climate.

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Section: Measuring 3-d Gw Propertiesmentioning

confidence: 99%

An 18‐Year Climatology of Directional Stratospheric Gravity Wave Momentum Flux From 3‐D Satellite Observations

Hindley

Wright

Hoffmann

et al. 2020

Geophysical Research Letters

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“…An earlier version of the software was used to apply the 3DST to 3-D AIRS measurements in Wright et al (2017) in a regional gravity wave study over the Southern Andes and Antarctic Peninsula. Later, Hu et al (2019) used the software to apply the 2DST to measure concentric gravity waves around z ≈ 90 km in airglow measurements from the day/night band of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. Other studies currently in progress include applying the 2DST to the study of waves around large-scale meteorological processes, and applying the 3DST to investigations of wave structures over small islands and hurricanes.…”

Section: The N -Dimensional Stockwell Transformmentioning

confidence: 99%

Gravity waves in the winter stratosphere over the Southern Ocean: high-resolution satellite observations and 3-D spectral analysis

Hindley¹,

Smith²,

Hoffmann³

et al. 2019

Preprint

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<p><strong>Abstract.</strong> Atmospheric gravity waves play a key role in the transfer of energy and momentum between layers of the Earth's atmosphere. However, nearly all Global Circulation Models (GCMs) seriously under-represent the momentum fluxes of gravity waves at latitudes near 60&#176;&#8201;S. This can result in modelled winter stratospheres that are unrealistically cold &#8211; a significant bias known as the "cold-pole problem". There is thus a need for measurements of gravity-wave fluxes near 60S to test and constrain GCMs. Such measurements are notoriously difficult, because they require 3-D observations of wave properties if the fluxes are to be estimated without using significant limiting assumptions. Here we use 3-D satellite measurements of stratospheric gravity waves from NASA's AIRS/Aqua instrument. We present the first extended application of a 3-D Stockwell transform (3DST) method to determine localised gravity-wave amplitudes, wavelengths and directions of propagation around the entire region of the Southern Ocean near 60&#176;&#8201;S during austral winter 2010. We first validate our method using a synthetic wave field and two case studies of real gravity waves over the Southern Andes and the island of South Georgia. A new technique to overcome wave amplitude attenuation problems in previous methods is also presented. We then characterise large-scale gravity-wave occurrence frequencies, directional momentum fluxes and short-timescale intermittency over the entire Southern Ocean. Our results show that highest wave-occurrence frequencies, amplitudes and momentum fluxes are observed in the stratosphere over the mountains of the Southern Andes and Antarctic Peninsula. However, we find that around 60&#8211;80&#8201;% of total zonal-mean momentum flux is located over the open Southern Ocean during June&#8211;August, where a large "belt" of increased wave-occurrence frequencies, amplitudes and fluxes is observed. Our results also suggest significant short-timescale variability of fluxes from both orographic and non-orographic sources in the region. A particularly striking result is a widespread convergence of gravity-wave momentum fluxes towards latitudes around 60&#176;&#8201;S from the north and south. We propose that this convergence, which is observed at nearly all longitudes during winter, accounts for a significant part of the under-represented flux in GCMs at these latitudes.</p>

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“…They used this method to extract the characteristics of the GW captured in a period of more than one month [17]. Hu et al [18] applied a two-dimensional (2D) Stockwell transform to detect and characterize the GWs in satellite images. However, to obtain more information (e.g., wavelength, period, phase speed, and GW climatology) from the large ASAI images, the processing method requires the capacity of locating the wave pattern areas with high efficiency, and robustness.…”

Section: Introductionmentioning

confidence: 99%

Automatic Extraction of Gravity Waves from All-Sky Airglow Image Based on Machine Learning

Lai

Yue

et al. 2019

Remote Sensing

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With the development of ground-based all-sky airglow imager (ASAI) technology, a large amount of airglow image data needs to be processed for studying atmospheric gravity waves. We developed a program to automatically extract gravity wave patterns in the ASAI images. The auto-extraction program includes a classification model based on convolutional neural network (CNN) and an object detection model based on faster region-based convolutional neural network (Faster R-CNN). The classification model selects the images of clear nights from all ASAI raw images. The object detection model locates the region of wave patterns. Then, the wave parameters (horizontal wavelength, period, direction, etc.) can be calculated within the region of the wave patterns. Besides auto-extraction, we applied a wavelength check to remove the interference of wavelike mist near the imager. To validate the auto-extraction program, a case study was conducted on the images captured in 2014 at Linqu (36.2°N, 118.7°E), China. Compared to the result of the manual check, the auto-extraction recognized less (28.9% of manual result) wave-containing images due to the strict threshold, but the result shows the same seasonal variation as the references. The auto-extraction program applies a uniform criterion to avoid the accidental error in manual distinction of gravity waves and offers a reliable method to process large ASAI images for efficiently studying the climatology of atmospheric gravity waves.

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Measuring Gravity Wave Parameters from a Nighttime Satellite Low-Light Image Based on Two-Dimensional Stockwell Transform

Cited by 9 publications

References 32 publications

An 18‐Year Climatology of Directional Stratospheric Gravity Wave Momentum Flux From 3‐D Satellite Observations

An 18‐Year Climatology of Directional Stratospheric Gravity Wave Momentum Flux From 3‐D Satellite Observations

Gravity waves in the winter stratosphere over the Southern Ocean: high-resolution satellite observations and 3-D spectral analysis

Automatic Extraction of Gravity Waves from All-Sky Airglow Image Based on Machine Learning

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