Tropical Cold Pool Characteristics

Convective cold pools are thought to significantly contribute to mesoscale convective organization. Various hypotheses exist regarding the role they play in tropical convection, with some suggesting that dynamical lifting is the organizing mechanism, while others emphasize the role played by the moist thermodynamic state of the cold pool itself. Long duration, large-domain, cloud-resolving model simulations conducted under a state of radiative convective equilibrium (RCE) have been used to assess the characteristics of tropical cold pools, and their role in the organization of tropical convection. As the tropical atmosphere is never too far from radiative convective equilibrium, this framework is suitable for examining such relationships.

The Regional Atmospheric Systems (RAMS) has been used to conduct these simulations using a grid that spans 3000 x 200 x 25 km in the zonal, meridional and vertical directions, respectively. The horizontal grid spacing is 1km, while a stretched grid is used in the vertical. Periodic lateral boundary conditions are utilized for both the zonal and meridional lateral boundaries. A fixed SST of 300K comprises the lower boundary condition. A TOGA COARE sounding is used to initialize the model, and convection is initiated using randomized perturbations to the potential temperature in the boundary layer. The simulations are conducted for 70 days. The last 20 days of the simulation are analyzed, representing the time period during which the simulated atmosphere is in radiative convective equilibrium. The spatial and temporal extent of these simulations produces a large sample of convective cold pools that develop under a wide range of different environmental conditions. A number of aspects of these cold pools will be presented including their frequency, area, depth, intensity, duration and recovery rates, as well as the dependency of these characteristics on the environmental conditions. Furthermore, relationships between these cold pool characteristics and precipitation rates, convective mass flux and convective organization will be discussed.