Multiple Scattering and CLOUDNET D.Donovan, J. Pelon and M. Haeffelin

Multiple scattering

Beam tends to spread out in Clouds

Effective extinction is reduced ½ energy goes into forward diffraction peak. For large particles and large FOV's F(z)=0.5

Dependence on size

Applicatio n to Real Data

An ice cloud example FOV 5mrad ? FOV 0.5 mrads Alignment ?

An lower cloud example GreenIR Overload ? Pick-up noise ?

A low water cloud example Green IR Alignment and overload Pickup-noise ?

So…inconclusive Hints that it may still work ! Need better data. Examining quick looks not enough ! Alignment drifts Non-linearity and Signal-induced-noise and noise pick-up Need purpose acquired data with signals within linear range of the system and attention to alignment !

Retrieval Procedure (for thick clouds) To get optical depth

Low water clouds (often missed by radars) Small FOV should be small as possible Large FOV of microns sensitive to variations between 5-25 microns Feasible ! Should be attempted

Semi-analytical model (Eloranta)