Understanding the Transition to Strong Convection in Realistic and Idealised Cloud-Resolving Simulations of Different Aggregation Scenarios

Abstract:

Recent empirical studies across a broad range of observational scales have attempted to characterize aspects of convective phenomena with a view to constraining convective parametrizations. In particular, some of them have tried to connect convective organization with theories of critical phenomena and statistical physics.

In this contribution, we analyse, from the perspective of critical phenomena, idealised and realistic runs of the Met Office Unified Model. The idealized run is 4km with a squared domain lateral size of 576 km with periodic lateral boundary conditions and 40 days with 3D Smagorinsky mixing and explicit convection. The other cases are real studies of organized convection with different level of aggregation with domains in the Indian ocean and the West Pacific ocean around the equator with lateral boundaries forced from ECMWF analyses.

Our study focuses on, on the one hand, the relationship between water vapour, precipitation and rainfall extremes. This transition is still not well characterized and previous work have found contradictory results between real data and models, as well as for different water vapour observables. We find differences between idealized and realistic runs with different aggregation levels. We try to explain such findings and investigate the effects of observational uncertanties in these relationships. On the other hand, we look at different statistical properties of clouds and precipitation, such as the energy distribution of convective clusters and study its scaling properties in time and space, including any dependence in the state of aggregation of the run.