Australia: The Land Where Time Began

A biography of the Australian continent 

Intensification of Convective Extremes Driven by Interaction Between Clouds

The response of convective-type cloud and precipitation to changes of temperature may have a key role in a changing climate (O’Gorman, 2012; Kendon et al., 2014; Tan, Rossow & Tselioudis, 2015). Yet, it has remained unclear if the intensities of convective precipitation intensities will increase mainly as a result of thermodynamic or dynamical processes (Westra et al., 2014). In this paper Moseley et al. report the results of performing large eddy simulations of convection by imposing a diurnal cycle of surface temperature that is realistic. They found that convective events slowly organised into cloud clusters that were larger and those events that occurred late in the day produced the highest precipitation intensities. It was shown by tracking rain cells throughout their life cycles, which events resulting from collisions respond strongly to boundary condition events, such as temperature changes. Conversely, events that do not result from collisions remain largely unaffected. More interaction between events and stronger extremes of precipitation do indeed result from an increase of surface temperature. When leaving temperature unchanged but simply allowing more time for self-organisation does however lead to comparable intensification. It is implied by these findings that the convective field as a whole acquires a memory of past precipitation and inter-cloud dynamics, which drives extremes. The results obtained by this study for projections of global climate models suggest the interaction between convective clouds must be incorporated to simulate convective extremes and the diurnal cycle more realistically.

Sources & Further reading

1. Moseley, C., C. Hohenegger, P. Berg and J. O. Haerter (2016). "Intensification of convective extremes driven by cloud-cloud interaction." Nature Geosci 9(10): 748-752.