Atmospheric inertia-gravity waves retrieved from level-2 data of the satellite microwave limb sounder Aura/MLS

Abstract

Abstract. The temperature profiles of the satellite experiment Aura/MLS are horizontally spaced by 1.5° or 165 km along the satellite orbit. These level-2 data contain valuable information about horizontal fluctuations in temperature, which are mainly induced by inertia-gravity waves. Wave periods of 2–12 h, horizontal wavelengths of 200–1500 km, and vertical wavelengths of 6–30 km efficiently contribute to the standard deviation of the horizontal temperature fluctuations. The study retrieves and discusses the global distributions of inertia-gravity waves in the stratosphere and mesosphere during July 2015 and January 2016. We find many patterns that were previously present in data of TIMED/SABER, Aura/HIRDLS, and ECMWF analysis. However, it seems that Aura/MLS achieves a higher vertical resolution in the gravity wave maps since the maps are derived from the analysis of horizontal fluctuations along the orbit of the sounding volume. The zonal mean of the inertia-gravity wave distribution shows vertical modulations with scales of 10–20 km. Enhanced wave amplitudes occur in regions of increased zonal wind or in the vicinity of strong wind gradients. Further, we find a banana-like shape of enhanced inertia-gravity waves above the Andes in the winter mesosphere. We find areas of enhanced inertia-gravity wave activity above tropical deep convection zones at 100 hPa (z ∼ 13 km). Finally, we study the temporal evolution of inertia-gravity wave activity at 100 hPa in the African longitude sector from December 2015 to February 2016.

Geographical distributions of mesospheric gravity wave activity before and after major sudden stratospheric warmings observed by Aura/MLS

“…We apply a similar data analysis as in Hocke et al (2016) who derived inertia-gravity wave activity from horizontal temperature perturbations observed by Aura/MLS. However, we found that the horizontal perturbations of geopotential height (GPH) are a better measure of mesospheric gravity wave activity.…”

“…In addition, we changed the averaging method of the global maps. Hocke et al (2016) derived at first daily maps of global gravity wave activity, and later they averaged for example 30 daily maps for getting the monthly average of gravity wave activity. In the present study, we are binning all observations of a month into the selected latitude-longitude grid yielding the monthly mean map of global gravity wave activity.…”

“…On the other hand, in case of three consecutive points the standard deviation and the mean are not well defined, and the measurement noise may dominate. Hocke et al (2016) estimated the response of the method by means of artificial sine waves (with different horizontal propa-15 gation directions) which are sampled with a spacing of 165 km along the sounding volume orbit. They found that the method includes some noise from high-frequency and medium-frequency gravity waves.…”

“…In the conclusions, they suggested a further study which retrieves inertia-gravity waves from the level2 data of Aura/MLS. Hocke et al (2016) followed this way and presented global distributions of inertia-gravity wave activity in the stratosphere and mesosphere based on temperature measurements of Aura/MLS.…”

Quasi 18-hour wave activity in ground-based observed mesospheric H<sub>2</sub>O over Bern, Switzerland

“…Space-borne temperature observations are often used to investigate gravity wave activity (Ern et al, 2004;Hocke et al, 2016).…”