Energy Spectra and Inertia–Gravity Waves in Global Analyses

Abstract

Several decades after E. Dewan predicted that the shallowing of the atmospheric energy spectrum in mesoscale is produced by the inertia–gravity (IG) waves, global analyses have reached the resolution at which the IG waves across many scales are resolved. The authors discuss the spatial filtering method based on the Hough harmonics that provides the temperature and wind perturbations associated with the IG waves in global analysis data. The method is applied to the ECMWF interim reanalysis and the operational 2014–16 analysis fields. The derived spectrum of IG wave energy is divided into three regimes: a part associated with the large-scale unbalanced circulations that has a slope close to −1 for zonal wavenumbers 1 ≤ k ≤ 6, a synoptic-scale range between 3000 and around 500 km (7 ≤ k ≲ 35) that is characterized by a nearly −5/3 slope, and a mesoscale range below 500 km where the slope of the IG energy spectrum in the 2015/16 analyses is steeper. In contrast, the energy spectrum of the Rossby waves has a −3 slope for all zonal wavenumbers k > 6. Presented results suggest that energy associated with the IG modes exceeds the level of energy associated with the Rossby waves around zonal wavenumber 35. The exact wavenumber depends on the season and considered atmospheric depth and it is suggested as a cutoff scale for studies of gravity waves.

Systematic decomposition of the MJO and its Northern Hemispheric extratropical response into Rossby and inertio‐gravity components

“…The present study makes use of the dataset denoted L57 in Žagar et al . (). It provides Rossby and IG components of the circulation between the surface and 0.8 hPa (the top three model levels were excluded).…”

“…Examples of such filtering for IG waves are shown in the work of Žagar et al . (), who discussed the spectrum of Rossby and IG waves in ERA‐Interim, as well as in the latest European Centre for Medium‐Range Weather Forecasts (ECMWF) operational analyses. The present study makes use of the dataset denoted L57 in Žagar et al .…”

Estimating Subseasonal Variability and Trends in Global Atmosphere Using Reanalysis Data

“…The scale where the subseasonal variance associated with the IG modes exceeds variance due to Rossby modes is at k ≈75 (Figure d; around 530 km in the tropics and 380 km in midlatitudes). This is not surprising as at this scale divergence‐dominated processes projecting on the IG modes prevail over quasi‐geostrophic dynamics in nature and in the ECMWF forecast model used as the basis for the reanalysis (Žagar et al, ). This property should nevertheless be considered as mainly produced by the model since at these scales the impact of observations might be significantly smoothed by global data assimilation modeling.…”

“…Differences between physical parametrizations in the models used to prepare reanalyses largely control the IG spectrum and energy transport across scales (e.g., Malardel & Wedi, ). The reanalyses underestimate spatial variability on smaller scales (Žagar et al, ) that effects temporal variability. A study of S S V I in different reanalyses in the light of their known deficiencies is under way.…”

Diagnostics of internal atmospheric wave saturation and determination of their characteristics in Earth's stratosphere from radiosonde measurements

“…The original method of identifying wave events and reconstructing IGW characteristics in planetary atmospheres we developed [Gubenko et al, 2008b[Gubenko et al, , 2011[Gubenko et al, , 2016a has been widely recognized by scientific community both in Russia and abroad. It is now being successfully used to study wave processes in the atmospheres of Earth [Horinouchi, Tsuda, 2009;Xiao, Hu, 2010;Rechou et al, 2014;Sacha et al, 2014;Noersomadi, Tsuda, 2017;Zagar et al, 2017] and Venus [Altieri et al, 2014;Peralta et al, 2015]. For example, Rechou et al [2014] have shown that numerical simulation data and analysis of independent radar and probe measurements in Earth's atmosphere demonstrate high efficiency of our method and high reliability of scientific results it yields.…”