Predictability of severe weather systems can be intrinsically limited at mesoscales due to the chaotic nature of moist convection. Small convective errors could rapidly propagate upscale and contaminate the weather forecast. Theoretical studies have found that a flow with a “-5/3” kinetic energy spectrum is susceptible to such upscale error propagation. With a high-resolution WRF simulation, we have confirmed a recent study demonstrating that squall lines, triggered in a horizontally homogeneous environment, are able to generate a background mesoscale kinetic energy spectrum with a -5/3 slope. In the present numerical study it is found that this -5/3 slope manifests itself at all the levels throughout the atmosphere, from the lower troposphere to the lower stratosphere. The present study computes the spectral kinetic energy budget for these simulations to further analyze the processes associated with the creation of the -5/3 spectrum. The buoyancy production generated by moist convection, while mainly injecting energy in the upper troposphere at small scales, could also contribute to larger scales, possibly due to the organization of convective cells into mesoscale convective systems. The latter injected energy is then transported by a gravity wave flux both upward and downward. Nonlinear interactions, associated with the velocity advection term, finally helps build the -5/3 slope through upscale/downscale propagation at all levels.

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*email: yus140@psu.edu
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