Effects of Vertical Wind Shear, Radiation, and Ice Clouds on Precipitation Distributions During a Landfall of Severe Tropical Storm, Bilis (2006)


Torrential rainfall responses to vertical wind shear, radiation, and ice clouds during the landfall of severe Tropical Storm, Bilis (2006) are investigated via a rainfall partitioning analysis of grid-scale sensitivity experiment data. The rainfall data are partitioned into eight types based on surface rainfall budget. The largest contributions to total rainfall come from local atmospheric moistening, water vapor convergence, and hydrometeor loss/convergence (Type 3; 29%) when the large-scale upward motions occurred only in the upper troposphere on 15 July 2006. When the large-scale upward motion center moved to the mid troposphere on 16 July, Type 3 hydrometeor loss/convergence (26%) plus local atmospheric drying, water vapor divergence, and hydrometeor loss/convergence (Type 5; 25%) show equally important contributions to total rainfall.

The exclusion of vertical wind shear primarily reduced Type 5 rainfall because of the weakened hydrometeor loss/convergence on 16 July. The removal of cloud radiative effects enhances Type 5 rainfall due to increased local atmospheric drying and hydrometeor loss/convergence on 15 July. The elimination of ice clouds generally reduced Type 2 rainfall through the decreases in local atmospheric drying, water vapor convergence, and hydrometeor gain/divergence and Type 3 rainfall over two days.

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