Parcel Model Simulation 17-March cloud #22

• Model = Young (1974, 1978, J. Atmos. Sci.), Rockicki, Kelly, DeMott

• Explicit nucleation of droplets & ice crystals

• Ice nucleation modes:

• Deposition (ice supersaturation)
• Contact (aerosol size, drop size, T)
• Condensation-freezing (T, CCN, SSw)
• Immersion-freezing (T, drop size)
• Homogeneous freezing < -40°C (T, drop molality)

• Particle growth & evaporation:

• Discrete size bins
• Snow crystal growth habits

Notes:

Young, K.C., 1974b: A numerical simulation of wintertime orographic precipitation: Part I. Description of model microphysics and numerical techniques. J. Atmos. Sci., 31, 1735-1748.

Some limitations should be recognized:

This is an adiabatic parcel model (no mixing)

The aircraft does not follow streamlines or particle trajectories

The measured CCN spectrum did not produce high enough droplet concentration, so it was fudged in order to obtain agreement.

Measurements of contact-freezing IN were not made. We used what was already in the model, ??