Quantifying the Importance of Cold Pool Mechanisms for Convection Triggering

For original submission and image(s), see ARM Research Highlights http://www.arm.gov/science/highlights/ Research Highlight The organization of the subcloud layer into cold pools, areas of evaporatively cooled downdraft air spreading on the surface, is one of the key processes that help sustainin deep convection. It has long been known cold pools can spawn new convective cells by mechanically lifting air along their gust front. Such lifting could be the result of the interaction of a cold pool with wind shear or sea breeze, or it could be caused by the collision of two or more cold pools. This triggering mechanism is often referred to as “mechanical forcing.” More recently, another mechanism, often referred to as “thermodynamic forcing,” has been suggested, leveraging on the fact that leading edges of cold pools typically present positive moisture anomalies. The enhanced water vapor content of cold pool parcels favors the generation of new convective cells because it can sensibly reduce the convective inhibition encountered by parcels once they start ascending. Although both mechanisms are expected to play a role in different scenarios, a quantification of their importance has not been investigated.