Determining the Environmental Parameters that Govern the Power Law Distribution of Convective System Lifetimes in the Tropical Western Pacific (TWP)
The distribution of system lifetimes follows a power law relationship consistent with that found in prior studies. For each convective system-type, categorized by lifetime, the thermodynamic and dynamic environment surrounding the system is analyzed to determine the parameters that dictate system growth (from a rainfall perspective) and system decay. Mesoscale surface wind convergence, divergence, mid-tropospheric relative humidity, boundary layer relative humidity, shear and atmospheric temperature perturbations at various levels are among the parameters analyzed. Among all parameters investigated, it is found that system growth, decay and longevity is tied to boundary layer temperature perturbations. The extent to which these temperature perturbations are associated with SST variations (i.e. an external, large-scale control) versus convective feedback (through downdrafts/cold pools) is discussed within the context of determining if large-scale environments or small-scale features and internal controls (leading to heterogeneity in the environment) are largely responsible for the observed power law distribution of system lifetimes. Such knowledge has implications for future convective parameterization efforts.