Dataset Information

Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

ABSTRACT: Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth's rotation and the atmosphere's stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia-gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia-gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia-gravity waves dominate at scales smaller than 500 km.

SUBMITTER: Callies J

PROVIDER: S-EPMC4260586 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Publications

Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

Callies Jörn J Callies Jörn J Ferrari Raffaele R Bühler Oliver O

Proceedings of the National Academy of Sciences of the United States of America 20141117 48

Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth's rotation and the atmosphere's stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at ho ...[more]

PMID: 25404349

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Project description:Abstract Gravity waves (GWs) generated by tropical convection are important for the simulation of large?scale atmospheric circulations, for example, the quasi?biennial oscillation (QBO), and small?scale phenomena like clear?air turbulence. However, the simulation of these waves still poses a challenge due to the inaccurate representation of convection, and the high computational costs of global, cloud?resolving models. Methods combining models with observations are needed to gain the necessary knowledge on GW generation, propagation, and dissipation so that we may encode this knowledge into fast parameterized physics for global weather and climate simulation or turbulence forecasting. We present a new method suitable for rapid simulation of realistic convective GWs. Here, we associate the profile of latent heating with two parameters: precipitation rate and cloud top height. Full?physics cloud?resolving WRF simulations are used to develop a lookup table for converting instantaneous radar precipitation rates and echo top measurements into a high?resolution, time?dependent latent heating field. The heating field from these simulations is then used to force an idealized dry version of the WRF model. We validate the method by comparing simulated precipitation rates and cloud tops with scanning radar observations and by comparing the GW field in the idealized simulations to satellite measurements. Our results suggest that including variable cloud top height in the derivation of the latent heating profiles leads to better representation of the GWs compared to using only the precipitation rate. The improvement is especially noticeable with respect to wave amplitudes. This improved representation also affects the forcing of GWs on large?scale circulation. Key Points Use of an idealized numerical model forced with radar?derived latent heat profiles to simulate convective gravity waves in the tropics Relating latent heat to rain rate and echo top height leads to improved representation of tropical GWs compared to satellite observations Approach could improve prediction of tropical gravity waves for weather forecasting and climate applications

Dataset Information

Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

Publications

Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

Similar Datasets

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