Clouds and Convection (Hans Ertel Research Group)

Group Leaders: Cathy Hohenegger and Opens window for sending emailDaniel Klocke (DWD)

 

Shallow and deep convective clouds are an important constituent of the atmosphere. Depending on the state of the land surface and of the atmosphere they may form, grow, organize in larger clusters, decay or die. Clouds not only respond to the environmental conditions but also significantly affect their surrouding, for instance through the formation and subsequent evaporation of precipitation. Allowing for a range of complex interactions amongst various processes and across scales, shallow and deep convective clouds pose a great challenge for atmospheric modeling at all scales.

 

Our group studies the statistical behavior of clouds, convection, boundary layer and microphysical processes holistically, with the goal of improving our understanding of and ability to represent and predict such processes in atmospheric models. Research questions that our group are addressing include:

 

  • Which physical processes control the size of clouds, their lifecycle, organization and other properties?
  • How strong is the coupling between convection and its environment  and what are the effects of misrepresented small-scale processes on larger scales?
  • How to formulate a parameterization that works across scales and that allows for realistic interactions between boundary layer, shallow and deep convection?

 

These questions are addressed by combining observations and atmospheric models of various complexity and horizontal resolution. Our main research tool are large-eddy simulations with horizontal resolution O(100 m) that allow an explicit representation of convective processes and provide detailed information on the cloud lifecycle. Such simulations are complemented with simulations performed at convection-permitting O(1-10 km) and coarser resolution O(> 10 km) to address the multi-scale challenges associated with the prediction of convection. Through the adopted methodology and research focus our group in essence seeks to bridge the gap between small and larger scales.

 

The Hans Ertel research group on clouds and convection is supported by the Max Planck Institute for Meteorology and by the German Weather Service through the  Hans Ertel Centre for Weather Research.

 

Recent and ongoing research topics

Lifecycle of convective clouds

- Characterization of the cloud size distribution

- Physical factors controlling the lifecycle of deep convection (cold pools, congestus moistening)

- Physical factors controlling the organization of precipitating convection

Coupling, role and misrepresentation of convection

-Interactions between deep convection (as isolated convective cells or squall lines) and the land surface

-Role of the diurnal cycle for convection/climate

-Importance of organization for climate

-Controls on and representation of convection over the Atlantic ITCZ and adjacent land

Parameterization development

-Formulation of a stochastic shallow convection scheme

-Representation of organization