Analysis of Trapped Small‐Scale Internal Gravity Waves Automatically Detected in Satellite Imagery.

In water vapor‐sensitive satellite imagery, small‐scale wave‐like perturbations of brightness temperature can be attributed to the presence of trapped internal waves in the troposphere. We present a method for detecting these local perturbations with wavelengths of about 10 km and apply it to imagery from the Advanced Baseline Imager on board the geostationary satellite GOES‐16. The algorithm allows us to analyze 4 years of sub‐hourly data in the southern part of the tropical eastern Pacific, where only a relatively low amount of medium and high clouds obscures the scene. By combining a measure of wave activity/trapping with ERA5 reanalysis data, we connect the occurrence of trapping with the presence of an increased upper‐tropospheric wind shear. This connection is more evident during December, January and February, when upper‐tropospheric jets are more likely. Our work supports existing case and model studies and is a step forward in the statistical and automated analysis of trapped small‐scale internal waves in the atmosphere. Plain Language Summary: Remote sensing instruments on satellites are able to measure the electromagnetic energy emitted by the Earth and the atmosphere. Certain wavelength ranges of the electromagnetic energy, called channels or bands of the respective instrument, can be related to relative humidity. Depending on the channel, these layers cover primarily the middle or the upper troposphere. Since atmospheric small‐scale waves influence the vertical structure of relative humidity, we analyze the resulting local horizontal variability in the satellite observations. We automatically detect these patterns over the eastern Pacific and explain why and when they occur during the season. Our work contributes to the identification of processes in the troposphere that can lead to hazardous weather. Key Points: Water vapor‐sensitive satellite imagery contains signatures of trapped internal waves that can be automatically detectedOver the eastern tropical Pacific, trapped internal waves in the upper troposphere are more likely during December, January, and FebruaryThe increased likelihood is due to sub‐seasonal intermittent absolute wind shear in combination with a more steady small buoyancy frequency [ABSTRACT FROM AUTHOR]