Simulating convective clouds with sustained supercooled liquid water down to -37.5 degrees C using a spectral microphysics model

Aircraft observations of highly supercooled water in convective clouds (1.8 gm(-3) at -37.5 degreesC) were reproduced by a numerical cloud model with explicit microphysical processes and turbulent effects. The model showed th at large concentrations of small cloud droplets induced by high concentrati ons of CCN and a strong updraft were essential in reproducing the observati ons. The same model reproduced microphysically maritime clouds with fast de pletion of cloud water by just changing the CCN spectrum. The constrains im posed by these extreme conditions revealed the weakness of existing cloud p arameterizations, and the necessity of inclusion of very detailed explicit microphysical and turbulent cloud processes in cloud models.