cloud (liq/ice) droplet radius and number concentrations

[andreasb]

Dear all,for a new module concerning atmospheric electricity I require droplet radii and number concentrations, and have a few questions on available variables:state%q(i,k,'NUMLIQ'/'NUMICE') are in the output labeled as "Grid box averaged cloud liquid number (kg/kg)" - does that mean for getting the number concentration INSIDE the cloud, I need to:

1. devide by cloud cover (cldn), and2. multiply by density That's assuming that the unit is "number of droplets/kg" rather than kg/kg, is that correct?I am currently using the variables 'rel' and 'rei' from pbuf, which are labeled "MG REI stratiform cloud effective radii". Do they only cover stratiform clouds? If so, are radii from other cloud types available also? What exactly is meant by "effective" - can I use this as an average radius to calculate a drop size distribution using standard techniques described e.g. by Pruppbacher and Klett?I am using CESM1.1 with CAM5 (MG).thanks!Andreas
(NCAR/HAO and UC)

 

[hannay]

Yes, NUMLIQ and NUMICE units are 1/kg (and not kg/kg). This bug has been fixed on the CAM trunk and it should in the next release.rei/rel are the effective radius for ice/liquid droplets in the stratiform clouds. This is used for radiation purpose.
The convective clouds are not seen by the radiation. However, we assume an effective radius to compute the detrained condensate from convective clouds.We set the effective radius to
- 8 microns for liquid and 25 microns for deep convection
- 10 microns for liquid and 50 microns for shallow convection"effective" in effective radius means that it is a weigthed mean of teh cloud droplet size.Hope this helps.   

 

[andreasb]

excellent, that's very helful, thank you very much Cecile!