Intercomparison of stratospheric gravity wave observations with AIRS and IASI

C I Meyer,L Hoffmann,C Clerbaux,M J Alexander,T Rößler,B Tournier,A W Grimsdell

doi:10.5194/amt-7-4517-2014

Abstract

Abstract. Gravity waves are an important driver for the atmospheric circulation and have substantial impact on weather and climate. Satellite instruments offer excellent opportunities to study gravity waves on a global scale. This study focuses on observations from the Atmospheric Infrared Sounder (AIRS) onboard the National Aeronautics and Space Administration Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the European MetOp satellites. The main aim of this study is an intercomparison of stratospheric gravity wave observations of both instruments. In particular, we analyzed AIRS and IASI 4.3 μm brightness temperature measurements, which directly relate to stratospheric temperature. Three case studies showed that AIRS and IASI provide a clear and consistent picture of the temporal development of individual gravity wave events. Statistical comparisons based on a 5-year period of measurements (2008–2012) showed similar spatial and temporal patterns of gravity wave activity. However, the statistical comparisons also revealed systematic differences of variances between AIRS and IASI that we attribute to the different spatial measurement characteristics of both instruments. We also found differences between day- and nighttime data that are partly due to the local time variations of the gravity wave sources. While AIRS has been used successfully in many previous gravity wave studies, IASI data are applied here for the first time for that purpose. Our study shows that gravity wave observations from different hyperspectral infrared sounders such as AIRS and IASI can be directly related to each other, if instrument-specific characteristics such as different noise levels and spatial resolution and sampling are carefully considered. The ability to combine observations from different satellites provides an opportunity to create a long-term record, which is an exciting prospect for future climatological studies of stratospheric gravity wave activity.

Highlights

Gravity waves play a key role in atmospheric dynamics and have substantial impact on weather and climate
This study focuses on nadir observations of two instruments, the Atmospheric Infrared Sounder (AIRS) onboard the National Aeronautics and Space Administration’s Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the European MetOp satellites
Many observational studies demonstrated that the Antarctic Peninsula is a hotspot of stratospheric gravity wave activity

Summary

Introduction

Gravity waves play a key role in atmospheric dynamics and have substantial impact on weather and climate. They transport energy and momentum, contribute to turbulence and mixing, and influence the mean circulation and thermal structure of the middle atmosphere (Lindzen, 1981; Holton, 1982, 1983). Gravity waves are important in the summer hemisphere where planetary wave activity is weak (Alexander and Rosenlof, 1996; Scaife et al, 2000). The most prominent sources of gravity waves are orographic generation (Smith, 1985; Durran and Klemp, 1987; Nastrom and Fritts, 1992; Dörnbrack et al, 1999) and convection (Pfister et al, 1986; Tsuda et al, 1994; Alexander and Pfister, 1995; Vincent and Alexander, 2000). The individual characteristics of the wave sources and the evolution of the wave spectrum with altitude-dependent wind and stability variations are important research topics today

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