Atmospheric Turbulence generated by energy at two scales: Balance Dynamics and Convective Energy Injection

Student Seminar Series

Department of Atmospheric & Oceanic Sciences

presents

a talk by

Aditya Baksi
PhD student

Atmospheric Turbulence generated by energy at two scales: Balance Dynamics and Convective Energy Injection

The atmosphere gets kinetic energy from radiatively forced temperature gradients at two main length scales: Baroclinic instability at wavelengths ≥ 3000 km (synoptic scales), and Convection at wavelength between hundreds to a few thousand meters (mesoscales). GCM studies, which are more realistically modeled large scale balanced dynamics, poorly resolve the convective scales. On the other hand, Mesoscale models, which better resolve the convective scales, don’t generally extend themselves to planetary scales to properly include the balance dynamics.

Lilly (1989) suggested that the atmospheric energy spectrum is at least partly produced by quasi-two dimensional turbulence, generated by energy sources at both large and small scales. Nastrom & Gage (1985) observed the atmospheric energy spectra against horizontal wavenumber showing two power law ranges: a steep -3 slope for synoptic scale range and a shallow -5/3 slope for mesoscale range. The study by Kafiabad & Bartello (2018) produced similar spectra, but doesn’t include forcing at small scales. Simulations can be designed by forcing at both the scales, such that they incorporate the effects of both the forward cascade of energy that is leaked from large scale balance dynamics and the convective injection of unbalanced energy at smaller scales.

Wednesday Nov 13/ 2.30 PM/ Room 934 Burnside Hall