Influences of environmental relative humidity and horizontal scale of subcloud ascent on deep convective initiation

A passive tracer analysis shows that the bulk fractional entrainment rate decreases rapidly with R-sub but depends little on phi(E). However, buoyancy dilution increases as either R-sub or phi(E) decreases; buoyancy above the level of free convection is rapidly depleted in dry environments when R-sub is small. While deep convective initiation occurs with an increase in relative humidity of the near environment from moistening by earlier convection, the importance of this moisture preconditioning is inconclusive as it is accompanied by an increase in R-sub.

Overall, it is concluded that small changes to R-sub driven by external forcing or by convection itself could be a dominant regulator of deep convective initiation.