Understanding the dynamic contribution to future changes in tropical precipitation from low level convergence lines

Future precipitation changes include contributions from both thermodynamic and dynamic processes. Given that precipitation in the tropics is commonly associated with convergence lines, we construct a simple linear regression model relating the convergence line frequency and strength to precipitation at sub-daily time-scales, and use it to show that changes in the convergence lines are related to the dynamical change in the precipitation. Given GCM-predicted convergence line changes, we predict precipitation changes using the regression model. The so predicted precipitation change is equivalent to the dynamical component of the precipitation change identified in earlier studies that used very different methods. The difference between the precipitation change in GCMs and that predicted from changes in convergence lines accounts for thermodynamic and other potentially important dynamical contributions. More accurate predictions of future precipitation therefore require the accurate simulations of the relatively short-lived weather features responsible for convergence lines in the tropics in GCMs.