Preprints
https://doi.org/10.5194/wcd-2021-68
https://doi.org/10.5194/wcd-2021-68

  15 Oct 2021

15 Oct 2021

Review status: this preprint is currently under review for the journal WCD.

Differentiating lightning in winter and summer with characteristics of wind-field and mass-field

Deborah Morgenstern1,2, Isabell Stucke1,2, Thorsten Simon2, Georg J. Mayr1, and Achim Zeileis2 Deborah Morgenstern et al.
  • 1Department of Atmospheric and Cryospheric Sciences (ACINN), University of Innsbruck, Austria
  • 2Department of Statistics, University of Innsbruck, Austria

Abstract. Lightning in winter (December, January, February, DJF) is rare compared to lightning in summer (June, July, August, JJA) in central Europe. The conventional explanation attributes the scarcity of winter lightning to seasonally low values of variables that create favorable conditions in summer. Here we systematically examine whether different meteorological processes are at play in winter. We use cluster analysis and principal component analysis and find physically meaningful groups in ERA5 atmospheric reanalysis data and lightning data for northern Germany. Two sets of conditions emerged: Wind-field-dominated and mass-field (temperature) dominated lightning conditions. Wind-field type lightning is characterized by increased wind speeds, high cloud shear, large dissipation of kinetic energy in the boundary layer, and moderate temperatures. Clouds are close to the ground and a relatively large fraction of the clouds is warmer than −10 °C. Mass-field type lightning is characterized by increased convective available potential energy (CAPE), the presence of convective inhibition (CIN), high temperatures, and accompanying large amounts of water vapor. Large amounts of cloud-physics variables related to charge separation such as ice particles and solid hydrometeors further differentiate both mass-field and wind-field lightning. Winter lightning is wind-field driven whereas in summer lightning is mostly mass-field driven with a small fraction of cases being wind-field driven. Consequently, typical weather situations for wind-field lightning in the study area in northern Germany are strong westerlies with embedded cyclones. For mass-field lightning, the area is typically on the anticyclonic side of a southwesterly jet.

Deborah Morgenstern et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on wcd-2021-68', Milind Sharma, 25 Oct 2021 reply
    • AC1: 'Reply on CC1', Deborah Morgenstern, 29 Oct 2021 reply
  • RC1: 'Comment on wcd-2021-68', Anonymous Referee #1, 24 Nov 2021 reply

Deborah Morgenstern et al.

Data sets

Differentiating lightning in winter and summer with characteristics of wind-field and mass-field: supplementary material Deborah Morgenstern, Isabell Stucke, Thorsten Simon, Georg J. Mayr, Achim Zeileis https://doi.org/10.5281/zenodo.5566840

Deborah Morgenstern et al.

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Short summary
Wintertime lightning in Central Europe is rare but has a large damage potential for tall structures such as wind turbines. We use a data-driven approach to explain why it even occurs when the meteorological processes causing thunderstorms in summer are absent. In summer with strong solar input, thunderclouds have a large vertical extent, whereas in winter thunderclouds are shallower in the vertical but tilted and elongated in the horizontal by strong winds that increase with altitude.