Turbulence and waves in a dry and moist tropical planet – Can we get large planetary scale structures from small scale tropical convection?

Seminar by Prof. Nili Harnik from Tel Aviv University

28 February 2023
KST 14:00 – 15:00

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

Satellite image-movies of clouds show an intricate variety of shapes of cloudy-areas moving around and changing constantly, on a multitude of spatial scales. Specifically, we see an organization of convection into coherent large scale structures, as part of moist tropical systems. These large scale moist systems, by diverse means, play a major role in shaping the kind of weather occurring during a given season, and are responsible for much of the extreme weather in the tropics. Spectral analysis of brightness temperatures – a proxy for deep convection- reveals peaks along linear dispersion relation curves for planetary scale waves, alongside a red noise spectrum. This coexistence of waves and turbulence in the tropics has not been studied before, and specifically, whether the planetary scale waves can be excited via an upscale turbulent cascade from mesoscale convective systems. We will examine this in a simple model run in tropical-planet configuration, in which there are no large-scale gradients in heating or sea surface temperatures. This allows us to examine these interactions without the influence of midlatitude weather. We find that mesoscale structures aggregate to larger scales only if vorticity anomalies are excited strongly enough. The process of convection aggregation from cloud scale to mesoscale has been extensively studied. Our study can be viewed as complementing these studies by examining the aggregation from mesoscale to planetary scales.