Convective Mass‐Flux From Long Term Radar Reflectivities Over Darwin, Australia
Alessandro Savazzi, Christian Jakob, A. Pier Siebesma
Abstract
Abstract Most cumulus parametrizations today make use of a simple conceptual model of convection, called the mass‐flux approach. This approach depicts convection as an ensemble of updrafts and downdrafts occurring within a model grid‐box. The aim of this study is to determine convective mass‐fluxes and their constituents on the scale of a 100 km GCM grid‐box from a C‐band polarimetric radar and thereafter investigate the relative role of area fraction and vertical velocity in determining the shape and magnitude of bulk mass‐flux profiles. We make use of observational estimates of these quantities spanning 13 wet seasons in the tropical region of Darwin. Following a bulk approach, the results show that the distribution of mass‐flux is positively skewed and its mean profile peaks at 4 km. This is the result of constant area fractions and increasing vertical velocities below that level. Above 4 km, in‐cloud vertical velocity plays a marginal role compared to the convective area fraction in controlling mass‐flux profiles.