Effects of moist convection on mesoscale predictability

In particular they found that moist processes were responsible for this strong initial-condition sensitivity of the 1 - 2-day prediction of mesoscale forecast aspects. In the present study they take a more systematic look at the processes by which small initial differences ("errors") grow in those numerical forecasts.

For initial errors restricted to scales below 100 km, results show that errors first grow as small-scale differences associated with moist convection, then spread upscale as their growth begins to slow. In the context of mesoscale numerical predictions with 30-km resolution, the initial growth is associated with nonlinearities in the convective parameterization (or in the explicit microphysical parameterizations, if no convective parameterization is used) and proceeds at a rate that increases as the initial error amplitude decreases.