Multi-instrument gravity-wave measurements over Tierra del Fuego and the Drake Passage – Part 1: Potential energies and vertical wavelengths from AIRS, COSMIC, HIRDLS, MLS-Aura, SAAMER, SABER and radiosondes

Abstract

Abstract. Gravity waves in the terrestrial atmosphere are a vital geophysical process, acting to transport energy and momentum on a wide range of scales and to couple the various atmospheric layers. Despite the importance of these waves, the many studies to date have often exhibited very dissimilar results, and it remains unclear whether these differences are primarily instrumental or methodological. Here, we address this problem by comparing observations made by a diverse range of the most widely used gravity-wave-resolving instruments in a common geographic region around the southern Andes and Drake Passage, an area known to exhibit strong wave activity. Specifically, we use data from three limbsounding radiometers (Microwave Limb Sounder, MLSAura; HIgh Resolution Dynamics Limb Sounder, HIRDLS; Sounding of the Atmosphere using Broadband Emission Radiometry, SABER), the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) GPS-RO constellation, a ground-based meteor radar, the Advanced Infrared Sounder (AIRS) infrared nadir sounder and radiosondes to examine the gravity wave potential energy (GWPE) and vertical wavelengths (λ z ) of individual gravity-wave packets from the lower troposphere to the edge of the lower thermosphere ( ∼ 100 km). Our results show important similarities and differences. Limb sounder measurements show high intercorrelation, typically > 0.80 between any instrument pair. Meteor radar observations agree in form with the limb sounders, despite vast technical differences. AIRS and radiosonde observations tend to be uncorrelated or anticorrelated with the other data sets, suggesting very different behaviour of the wave field in the different spectral regimes accessed by each instrument. Evidence of wave dissipation is seen, and varies strongly with season. Observed GWPE for individual wave packets exhibits a log-normal distribution, with short-timescale intermittency dominating over a wellrepeated monthly-median seasonal cycle. GWPE and λ z exhibit strong correlations with the stratospheric winds, but not with local surface winds. Our results provide guidance for interpretation and intercomparison of such data sets in their full context.

A two-dimensional Stockwell transform for gravity wave analysis of AIRS measurements

“…As discussed in previous studies (e.g. Wright and Gille, 2013;Wright et al, 2015), there are likely to be multiple peaks in |κ(k x , k y )| corresponding to overlapping waves at the same location in h(x, y). Indeed, in Fig.…”

“…The weighting function of the 667.77 cm −1 channel peaks near 3 hPa (∼ 40 km), with a full width at half maximum of ∼ 12 km (Alexander and Barnet, 2007, also illustrated in Fig. 1 of Wright et al, 2016a). Gravity waves with vertical wavelengths shorter than 12 km are thus unlikely to be resolved and vertical wavelengths close to this limit will be strongly attenuated.…”

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

“…Evidence of wave dissipation is seen and varies strongly with season. A first combination of nadir instrument (AIRS) and limb instrument (MLS) observations was done by Wright et al (2016b), who analyzed the wave momentum flux and the full 3-D direction of propagation for a mountain wave case study over the Andes. In contrast to these three studies, we focus on a global statistical comparison of a nadir instrument (AIRS) and a limb instrument (HIRDLS) over a measurement period of 3 years.…”

Mountain waves modulate the water vapor distribution in the UTLS

“…The uncertainty is ±5 % at a sampling rate of 25 Hz. On 4 July, 16 dropsondes were launched by a fully automated Airborne Vertical Atmospheric Profiling System (AVAPS) (Young et al, 2014). The dropsondes (Vaisala, Inc.) contain sensors to measure atmospheric temperature, pressure and humidity and a GPS receiver to derive winds.…”

“…Gravity waves are known to play an important role in the circulation, structure and variability of the atmosphere (Fritts and Alexander, 2003). They distribute energy and momentum horizontally and vertically in the atmosphere (e.g., Smith et al, 2008;Geller et al, 2013;Wright et al, 2016).…”