Effects of large-scale forcing and ice clouds on pre-summer heavy rainfall over southern China in June 2008: A partitioning analysis based on surface rainfall budget

The effects of large-scale forcing and ice clouds on rainfall are studied by analyzing a series of sensitivity experiments of a pre-summer heavy rainfall event over southern China from 3 to 8 June 2008. The analysis is conducted categorizing grid-scale rainfall simulation data into eight rainfall types based on different rainfall processes. The rainfall with water vapor divergence and local atmospheric drying and hydrometeor loss/convergence (TfM) has the largest contribution to total rainfall during the development of rainfall when the imposed large-scale forcing produces water vapor convergence. TfM and the rainfall with water vapor convergence and local atmospheric moistening and hydrometeor loss/convergence (tFM) have the largest contributors to total rainfall during the decay phase when the imposed large-scale forcing generates water vapor divergence. TfM becomes the largest contributor during the decay phase when the exclusion of ice clouds decreases tFM and increases TfM. The removal of ice clouds enhances the contribution of the rainfall with water vapor convergence to total rainfall during the life span of the rainfall event.

Research Highlights
► The largest rain (TfM) is related to divergence and drying during rain development.
► The largest rains are TfM and tFM (convergence and moistening) in decay phase.
► TfM becomes larger than tFM in decay phase when ice clouds are excluded.
► The removal of ice clouds enhances the rainfall with convergence during rain event.