Abstract
AbstractAtmospheric gravity waves (GWs) are key drivers of the atmospheric circulation, but their representation in general circulation models (GCMs) is challenging, leading to significant biases in middle atmospheric circulations. Unresolved GW momentum transport in GCMs must be parameterized, but global directional GW observations are needed to constrain this. Here we present an 18‐year climatology of directional stratospheric GW momentum flux (GWMF) from global AIRS/Aqua 3‐D satellite observations during 2002 to 2019. Striking hemispheric asymmetries are found at high latitudes, including dramatic reductions and reversals of GWMF during sudden stratospheric warmings. During Southern Hemisphere winter, a lateral convergence of GWMF toward 60°S is found that has no Northern Hemisphere counterpart. In the tropics, we find that zonal GWMF in AIRS measurements is strongly modulated by the semiannual oscillation (SAO) but not the quasi‐biennial oscillation (QBO). Our results provide guidance for future GW parameterizations needed to resolve long‐standing biases in GCMs.
Highlights
The accurate representation of atmospheric gravity waves (GWs) in general circulation models (GCMs) has been a major challenge for the atmospheric dynamics community in recent years (e.g., Alexander et al, 2010; Fritts & Alexander, 2003; Fritts et al, 2006; Geller et al, 2013; Plougonven et al, 2020)
We find that zonal GW momentum flux (GWMF) in AIRS measurements is strongly modulated by the semiannual oscillation (SAO) but not the quasi‐biennial oscillation (QBO)
We present multidecadal global measurements of directional GW momentum flux derived from 3‐D satellite observations from National Aeronautics and Space Administration's (NASA's) AIRS instrument
Summary
The accurate representation of atmospheric gravity waves (GWs) in general circulation models (GCMs) has been a major challenge for the atmospheric dynamics community in recent years (e.g., Alexander et al, 2010; Fritts & Alexander, 2003; Fritts et al, 2006; Geller et al, 2013; Plougonven et al, 2020). The development of a 3‐D temperature retrieval for AIRS/Aqua by Hoffmann and Alexander (2009), combined with the development of 3‐D spectral analysis techniques for GW measurements (Ern et al, 2017; Hindley et al, 2019; Lehmann et al, 2012; Wright et al, 2017), has allowed global 3‐D GW measurements to be made These 3‐D measurements can provide directional GWMF climatologies, which can inform and constrain future parameterizations in GCMs. As discussed by Plougonven et al (2020), it is not a straightforward process to take GW measurements and convert them directly into model parameterizations, but global directional GWMF measurements are an essential missing piece of the puzzle.
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