1. C=0.3D +/- 25% Realistic range of aspect ratios: - columns, plates, branched, dendrites Auer & Veal (1970) sizes 100 to 1mm - bullet rosette arm widths from in-situ obs Um & McFarquhar (2007)

2. Use capacitance to correlate ventilation coefficient data Much easier to estimate from aircraft data than L*, and correlates the data better Correlates available data to within 20%

3. Forward modelling radar & lidar Doppler velocities - Now recording full radar Doppler spectra at Chilbolton - lots of information to test the model, esp. particle fall speed relationship, size distribution… - New Doppler lidar - sensitive to small crystals: does the model represent these acceptably? For a given IWC and T (& to a lesser extent P), the model predicts a particular size distribution and fall speeds - use scattering model to calculate radar Doppler spectra - compare observed PDFs to model values - do crystals fall too fast or slow? - are there enough small particles? - is the size distribution too narrow/broad, etc…

4. Step 1 - sensitivities to choice of scattering model? Black = 35 GHz Red = 94 GHz IWC = 10 -5 kg/m 3 T=-30C Rayleigh scattering, both scattering models give similar results at 35 & 94 IWC = 10 -3 kg/m 3 T=-10C - significant differences at 94 - better agreement at 35 CloudSat comparisons - may explain why model cant predict high enough Z in thick frontal clouds? 9.3dBZ, 0.91m/s 1.5dBZ, 0.69m/s 11.2dBZ, 0.99m/s 8.2dBZ, 0.89m/s -11.8dBZ, 0.44m/s -12.0dBZ, 0.44m/s -11.9dBZ, 0.44m/s -12.5dBZ, 0.43m/s Mie theory (spheres) - Rayleigh-Gans (aggregates) --

5. Next step - how best to compare forward modelling to observations?