Preprints
https://doi.org/10.5194/egusphere-2023-1537
https://doi.org/10.5194/egusphere-2023-1537
12 Jul 2023
 | 12 Jul 2023

Diabatic effects on the evolution of storm tracks

Andrea Marcheggiani and Thomas Spengler

Abstract. Despite the crucial role of moist diabatic processes in midlatitude storm tracks and related model biases, we still lack a more complete theoretical understanding of how diabatic processes affect the evolution of storm tracks. To alleviate this shortcoming, we investigate the role of diabatic processes in the evolution of the Northern Hemispheric storm tracks using a framework based on the tendency of the slope of isentropic surfaces as a measure of baroclinic development.

We identify opposing behaviours in the near-surface and free troposphere for the relationship between the flattening of the slope of isentropic surfaces and its restoration by diabatic processes. Near the surface (900–800hPa), cold air advection associated with cold air outbreaks initially acts to flatten isentropic surfaces, with air–sea interactions ensuing to restore surface baroclinicity. In the free troposphere (750–350hPa), on the other hand, diabatic generation of slope of isentropic surfaces precedes its depletion due to tilting by eddies, suggesting the primary importance of moist diabatic processes in triggering subsequent baroclinic development. The observed phasing of the diabatic and tilting tendencies of the slope is observed both in upstream and downstream sectors of the North Atlantic and North Pacific storm tracks, rendering the phasing a general feature of midlatitude storm tracks.

In addition, we find a correspondence between the diabatic generation of slope of isentropic surfaces and enhanced precipitation as well as moisture availability, further underlining the crucial role of moisture and moist processes in the self-maintenance of storm tracks.

Andrea Marcheggiani and Thomas Spengler

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1537', Maarten Ambaum, 18 Jul 2023
    • AC1: 'Reply on RC1', Andrea Marcheggiani, 17 Sep 2023
  • RC2: 'Comment on egusphere-2023-1537', Anonymous Referee #2, 18 Aug 2023
    • AC2: 'Reply on RC2', Andrea Marcheggiani, 17 Sep 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1537', Maarten Ambaum, 18 Jul 2023
    • AC1: 'Reply on RC1', Andrea Marcheggiani, 17 Sep 2023
  • RC2: 'Comment on egusphere-2023-1537', Anonymous Referee #2, 18 Aug 2023
    • AC2: 'Reply on RC2', Andrea Marcheggiani, 17 Sep 2023

Andrea Marcheggiani and Thomas Spengler

Andrea Marcheggiani and Thomas Spengler

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Short summary
There is a gap between theoretical understanding and model representation of moist diabatic effects on the evolution of storm tracks. We seek to bridge this gap by exploring the relationship between diabatic and adiabatic contributions to changes in baroclinicity. We find opposing behaviours in the lower and upper troposphere in the maintenance of baroclinicity. In particular, our study reveals a link between higher moisture availability and upper-tropospheric restoration of baroclinicity.