Diagnosis of Dynamical Parameters in Torrential Rain Associatedwith Typhoon "Bilis" in 2006

High-resolution numerical simulation data of typhoon Bilis in 2006 was used for diagnostic analysis of eight dynamical parameters in a torrential rain event associated with Bilis. The eight parameters are moist thermodynamic advection parameter (G), the vertical component of the generalized convective vorticity vector (CVZ^*), moisture helicity (H_m), thermal helicity (H_t), divergence vertical flux (Γ), thermal divergence vertical flux (Γ_t), thermodynamic shear advection parameter (J), and generalized Q -vector divergence (Q^*_d). The results show that the following. (1) All eight dynamical parameters show strong signals in torrential rainfall regions. The correlation coefficients of the rain rate and H_m, H_t, Γ, Γ_t are all larger than 0.99, while the correlation coefficients of the total cloud hydrometeors and the four parameters above are all larger than 0.97. The correlation coefficients between J and rain rate, and J and total hydrometeors are both about 0.5, which is the lowest. (2) Q^*_d first increases and then decreases with an increase in rainfall intensity, sharing the same variation as the melting of graupel. J shows an increasing-decreasing-increasing pattern, while the other six parameters always increase with an increase in rainfall intensity, sharing the same variation pattern as the accretion of cloud water by rain water. (3) Overall, H_m, H_t, Γ and Γ_t correspond better with the rain rate and total cloud-microphysical processes associated with rain water. Thus, they are more indicative of strong precipitation.