Cascade

Cascade is a NERC funded consortium project to study organized convection in the tropical atmosphere using large domain cloud system resolving model simulations.

Convection in the tropics is organized across a wide range of space and time scales from a few kilometres and a few hours associated with individual cloud systems, through the mesoscale (10's-100's km, 1-2 days) associated with squall lines and cloud clusters and the synoptic scale (100's-1000's km, 3-10 days) associated with tropical cyclones, African Easterly Waves and equatorially trapped waves up to several thousand kilometres and 30-60 days associated with the Madden-Julian Oscillation. In addition to the intrinsic timescales of these systems, the diurnal cycle plays an important role in triggering and modulating these systems. Many of these scales of organization are poorly captured by weather and climate models and the interactions between these scales a poorly understood, yet may be fundamental to the tropical climate system.

Simulations to study the interactions between these different scales require sufficiently high resolution to be able to resolve the individual cloud systems and a large enough domain to capture the largest of these organizing scales. Until recently, computational resources have limited our ability to perform such simulations, but advances in computing power mean that they are now becoming possible. Cascade will exploit these new resources to improve our understanding of the scale interactions in organized tropical convection and our ability to simulate these systems in global climate and weather forecasting models.

Composite of IR satellite images from 18 September 2007 showing the range of scales of organization of tropical convection