Preprints
https://doi.org/10.5194/egusphere-2024-552
https://doi.org/10.5194/egusphere-2024-552
18 Mar 2024
 | 18 Mar 2024
Status: this preprint is open for discussion.

A global analysis of the fractal properties of clouds revealing anisotropy of turbulence across scales

Karlie N. Rees, Timothy J. Garrett, Thomas D. DeWitt, Corey Bois, Steven K. Krueger, and Jérôme C. Riedi

Abstract. The deterministic motions of clouds and turbulence, despite their chaotic nature, nonetheless follow simple statistical power-law scalings: a fractal dimension D relates individual cloud perimeters p to measurement resolution, and turbulent fluctuations scale with separation distance through the Hurst exponent ℌ. It remains uncertain whether atmospheric turbulence is best characterized by split isotropy that is three-dimensional with ℌ = 1/3 at small scales and two-dimensional with ℌ = 1 at large scales, or by wide-range anisotropic scaling with an intermediate value of ℌ. Here, we introduce an “ensemble fractal dimension” De – analogous to D – that relates the total cloud perimeter per domain area 𝒫 as seen from space to measurement resolution, and show theoretically how turbulent dimensionality and cloud edge geometry are linked through ℌ =De − 1. Observationally, by progressively coarsening the resolution of cloud mask arrays from various global satellite platforms and a numerical simulation of a tropical domain we find the scaling De ~ 5/3, or ℌ ~ 2/3, a value nearly consistent with a previously proposed “23/9D” anisotropic turbulent scaling. Remarkably, the same scaling links two “limiting case” estimates of 𝒫 evaluated at the planetary scale and the Kolmogorov microscale, as separated by 11 orders of magnitude, suggesting that cloud and turbulent behaviors are constrained by basic planetary parameters.

Karlie N. Rees, Timothy J. Garrett, Thomas D. DeWitt, Corey Bois, Steven K. Krueger, and Jérôme C. Riedi

Status: open (until 13 May 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Karlie N. Rees, Timothy J. Garrett, Thomas D. DeWitt, Corey Bois, Steven K. Krueger, and Jérôme C. Riedi
Karlie N. Rees, Timothy J. Garrett, Thomas D. DeWitt, Corey Bois, Steven K. Krueger, and Jérôme C. Riedi

Viewed

Total article views: 119 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
83 34 2 119 4 1
  • HTML: 83
  • PDF: 34
  • XML: 2
  • Total: 119
  • BibTeX: 4
  • EndNote: 1
Views and downloads (calculated since 18 Mar 2024)
Cumulative views and downloads (calculated since 18 Mar 2024)

Viewed (geographical distribution)

Total article views: 154 (including HTML, PDF, and XML) Thereof 154 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 13 Apr 2024
Download
Short summary
The shapes of clouds viewed from space reflect both vertical and horizontal motions in the atmosphere. The turbulence that shapes clouds is similarly described and related theoretically to the measured complexity of cloud perimeters from various satellites and a numerical model. We find agreement between theory and observations, and, remarkably, that the theory applies globally using only basic planetary physical parameters from the smallest scales of turbulence to the planetary scale.