1. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD Sensitivity Tests Regarding Assumed Graupel Particle Properties Motivation: Gilmore et al (MWR 2004) found high sensitivity to assumed graupel/hail particle properties in simulations of idealized convection. Can in LMK graupel particle properties changed to more hail-like properties help to reduce problem of underestimation of convection?

2. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD

3. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD Sensitivity Tests Regarding Assumed Graupel Particle Properties Intercept parameter N0 in particle size distribution N0 = 4*10 4 m -4, N0 = 4*10 5 m -4, N0 = 4*10 6 m -4 (currently: N0 = 4*10 6 m -4 ) Graupel density rho  0,2 g/cm 3, rho = 0,4 g/cm 3, rho = 0,9 g/cm 3 (currently: rho  0,2 g/cm 3) Both variations change graupel properties toward those of hail-like particles.

4. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD Idealized Convection (dx=2.8 km,3d Weisman-Klemp warm bubble, strong vertical (unidirectional) wind shear, --> symmetric cell-splitting) Total precipitation (TotP, in Gg), total graupel precipitation (TotG, in Gg), maximum precipitation (MaxP, in mm), maximum graupel precipitation (MaxG, in mm), after 2 hours.

5. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD Standard LME scheme no graupel (snow only) Graupel (as currently used) N0 = 4*10 6 m -4 rho  0,2 g/cm 3 Hail-like graupel N0 = 4*10 4 m -4 rho = 0,9 g/cm 3 precipitation after 2 h in mm Idealized Convection (dx=2.8 km,3d Weisman-Klemp warm bubble, strong vertical (unidirectional) wind shear, --> symmetric cell-splitting)

6. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD LMK Simulation of 7th Aug 2004 Weather Situation Mean total precipitation (MeanP, in mm), mean total graupel precipitation (MeanG, in mm), maximum precipiation (MaxP, in mm), maximum graupel precipiation (MaxG, in mm), after 23 hours.

7. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD rho  0, 2 g/cm 3 N0 = 4*10 6 m -4 rho  0, 9 g/cm 3 N0 = 4*10 4 m -4 LM scheme no graupel radar

8. Aktionsprogramm 2003 - Thorsten Reinhardt, DWD Conclusion In LMK simulations of idealized strong convection simulated precipitation can be highly sensitive to the assumed graupel particle properties. This sensitivity was much weaker in simulations of real weather situations. Changing graupel properties toward those of more hail-like properties does not cure problem of underestimated convection in LMK. Therefore a change in the parameterization of the graupel category in the microphysics scheme was not introduced.