17:15 〜 19:15
[ACG44-P01] Monitoring and Analysis of Atmospheric Gravity Wave Horizontal Propagation Using Thermal Satellite Imagery from Himawari-8/9
キーワード：Atmospheric Gravity Waves, Himawari-8/9, temporal high-pass filter, CWT, Momentum flux
Atmospheric Gravity Waves (AGWs) play a crucial role in atmospheric dynamics through both vertical and horizontal propagation, transferring momentum and energy across layers of the atmosphere. While the vertical propagation of AGWs is well understood and incorporated into global climate models through parameterization, the horizontal propagation remains poorly validated. This gap arises due to the lack of comprehensive global observations that can accurately assess its impact on the mean atmospheric flow. As a result, horizontal propagation has yet to be integrated into climate models, potentially causing discrepancies between simulated and observed atmospheric behavior.
Conventional methods, such as radiosondes, lidar, radar, and aircraft measurements, have attempted to detect AGWs’ horizontal propagation. However, these methods are often limited by high observation costs, restricted fields of view, and temporal constraints, making them unsuitable for large-scale, continuous monitoring. Unlike conventional methods, geostationary satellite imagery—such as that provided by GOES and Himawari-8/9—offers high spatiotemporal resolution and continuous monitoring, making it an ideal tool for studying AGWs on a large scale. By combining satellite imagery with a set of signal analyses, it has been proven possible to extract the atmospheric wave signal from the water vapor bands. However, the physical properties of AGWs’ horizontal propagation, for instance, the wave period, the wave propagation speed, the wavelength, and its dispersion relation, have never been extracted and confirmed, limiting our understanding of the role of horizontal propagation in atmospheric momentum transfer, Clear Air Turbulence (CAT) generation, and AGWs-induced drag.
This study analyzes satellite images in the 6.2, 6.9, and 7.3 μm water vapor bands from Himawari-8/9. A temporal high-pass filter is applied, followed by the use of pixel-wise 1D Continuous Wavelet Transform (CWT) to extract the wave period, 2D Fast Fourier Transform (2D FFT) to identify the wavelength, and Image Correlation for Thermal Image Velocimetry (TIV) to determine the wave propagation speed. The wave physical properties were used to confirm the AGWs dispersion relation in a midfrequency range. The results demonstrate that the applied methods effectively extract AGWs’ physical properties from geostationary satellite thermal images. Lastly, these findings also demonstrate an improved gravity wave momentum flux estimation in vertical directions through geostationary satellite images which can be applied together with data assimilation within climate models for better AGWs parameterization.
Conventional methods, such as radiosondes, lidar, radar, and aircraft measurements, have attempted to detect AGWs’ horizontal propagation. However, these methods are often limited by high observation costs, restricted fields of view, and temporal constraints, making them unsuitable for large-scale, continuous monitoring. Unlike conventional methods, geostationary satellite imagery—such as that provided by GOES and Himawari-8/9—offers high spatiotemporal resolution and continuous monitoring, making it an ideal tool for studying AGWs on a large scale. By combining satellite imagery with a set of signal analyses, it has been proven possible to extract the atmospheric wave signal from the water vapor bands. However, the physical properties of AGWs’ horizontal propagation, for instance, the wave period, the wave propagation speed, the wavelength, and its dispersion relation, have never been extracted and confirmed, limiting our understanding of the role of horizontal propagation in atmospheric momentum transfer, Clear Air Turbulence (CAT) generation, and AGWs-induced drag.
This study analyzes satellite images in the 6.2, 6.9, and 7.3 μm water vapor bands from Himawari-8/9. A temporal high-pass filter is applied, followed by the use of pixel-wise 1D Continuous Wavelet Transform (CWT) to extract the wave period, 2D Fast Fourier Transform (2D FFT) to identify the wavelength, and Image Correlation for Thermal Image Velocimetry (TIV) to determine the wave propagation speed. The wave physical properties were used to confirm the AGWs dispersion relation in a midfrequency range. The results demonstrate that the applied methods effectively extract AGWs’ physical properties from geostationary satellite thermal images. Lastly, these findings also demonstrate an improved gravity wave momentum flux estimation in vertical directions through geostationary satellite images which can be applied together with data assimilation within climate models for better AGWs parameterization.