The Mesoscale Forcing of a Midlatitude Upper-Tropospheric Jet Streak by a Simulated Convective System. Part II: Kinetic Energy and Resolution Analysis

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  • 1 Space Science and Engineering Center, University of Wisconsin-Madison, Madison, Wisconsin
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Abstract

A kinetic energy (KE) analysis of the forcing of a mesoscale upper-tropospheric jet streak by organized diabaaic processes within the simulated convective system (SCS) that was discussed in Part I is presented in this study. The relative contributions of the ageostrophic components of motion to the generation of KE of the convectively generated jet streak are compared, along with the KE generation by the rotational (nondivergent) and irrotational (divergent) mass transport. The sensitivity of the numerical simulations of SCS development to resolution is also briefly examined. Analysis within isentropic coordinates provides for an explicit determination of the influence of dramatic processes on the generation of KE.

The upper-level production of specific KE is due predominantly to the inertial advective ageostrophic component (IAD), and as such represents the primary process through which the KE of the convectively generated jet streak is realized. A secondary contribution by the inertial diabatic (IDI) term is observed. Partitioning the KE generation into its rotational and irrotational components reveals that the latter, which is directly linked to the diabatic heating within the SCS through isentropic continuity requirements, is the ultimate source of KE generation as the global area integral of generation by the rotational component vanishes. Comparison with an identical dry simulation reveals that the net generation of KE must be attributed to latent beating. Both the IAD and IDI ageostrophic components play important roles in this regard.

Examination of results frown simulations conducted at several resolutions supports the previous findings in that the effects of diabatic processes and ageostrophic motion on KE generation remain consistent. Resolution does impact the location and timing of SCS development, a result that has important implications in forecasting the onset of convection that develops from evolution of the large-scale flow and moisture transport. Marked differences are observed in the momentum field aloft subsequent to the lift cycle of the SCS in the 1°, 30-level base case (MP130) simulation discussed in Part I versus its 2° counterparts in that the MP130 simulation with higher spatial resolution contains from 14% to 30% more total KE.

Abstract

A kinetic energy (KE) analysis of the forcing of a mesoscale upper-tropospheric jet streak by organized diabaaic processes within the simulated convective system (SCS) that was discussed in Part I is presented in this study. The relative contributions of the ageostrophic components of motion to the generation of KE of the convectively generated jet streak are compared, along with the KE generation by the rotational (nondivergent) and irrotational (divergent) mass transport. The sensitivity of the numerical simulations of SCS development to resolution is also briefly examined. Analysis within isentropic coordinates provides for an explicit determination of the influence of dramatic processes on the generation of KE.

The upper-level production of specific KE is due predominantly to the inertial advective ageostrophic component (IAD), and as such represents the primary process through which the KE of the convectively generated jet streak is realized. A secondary contribution by the inertial diabatic (IDI) term is observed. Partitioning the KE generation into its rotational and irrotational components reveals that the latter, which is directly linked to the diabatic heating within the SCS through isentropic continuity requirements, is the ultimate source of KE generation as the global area integral of generation by the rotational component vanishes. Comparison with an identical dry simulation reveals that the net generation of KE must be attributed to latent beating. Both the IAD and IDI ageostrophic components play important roles in this regard.

Examination of results frown simulations conducted at several resolutions supports the previous findings in that the effects of diabatic processes and ageostrophic motion on KE generation remain consistent. Resolution does impact the location and timing of SCS development, a result that has important implications in forecasting the onset of convection that develops from evolution of the large-scale flow and moisture transport. Marked differences are observed in the momentum field aloft subsequent to the lift cycle of the SCS in the 1°, 30-level base case (MP130) simulation discussed in Part I versus its 2° counterparts in that the MP130 simulation with higher spatial resolution contains from 14% to 30% more total KE.

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