The Spatiotemporal Variability of Nonorographic Gravity Wave Energy and Relation to Its Source Functions

Abstract

The way the large-scale flow determines the energy of the nonorographic mesoscale inertia–gravity waves (IGWs) is theoretically significant and practically useful for source parameterization of IGWs. The relations previously developed on the f plane for tropospheric sources of IGWs including jets, fronts and convection in terms of associated secondary circulations strength are generalized for application over the globe. A lowpass spatial filter with a cut-off zonal wavenumber of 22 is applied to separate the large-scale flow from the IGWs using the ERA5 data of ECMWF for the period 2016–2019. A comparison with GRACILE data based on satellite observations of the middle stratosphere shows reasonable representation of IGWs in the ERA5 data despite underestimates by a factor of smaller than three. The sum of the energies, which are mass-weighted integrals in the troposphere from the surface to 100 hPa, as given by the generalized relations is termed initial parameterized energy. The corresponding energy integral for the IGWs is termed the diagnosed energy. The connection between the parameterized and diagnosed IGW energies is explored with regression analysis for each season and six oceanic domains distributed over the globe covering the Northern and Southern Hemispheres and the Tropics. While capturing the seasonal cycle, the domain area-average seasonal mean initial parameterized energy is weaker than the diagnosed energy by a factor of three. The best performance in regression analysis is obtained by using a combination of power and exponential functions which suggests evidence of exponential weakness.

Ein semi-implizites pseudo-inkompressibles Finite-Volumen Modell zur Simulation diabatischer Atmosphärenprozesse

“…Palmer et al, 1986;McFarlane, 1989;Song und Chun, 2008;Kim et al, 2013), stellt die derzeit noch strömungsunabhängige und stark angepasste Beschreibung der spontanen Schwerewellenaktivität (z.B. de la Cámara und Lott, 2013), welche in Jet-Front Systemen beobachtet wird, innerhalb der Modelle weiterhin einen großen Unsicherheitsfaktor dar (Amiramjadi et al, 2020) Zusammenhang als besonders geeignet herausstellen (Held, 2005).…”