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wrf_user_getvar cloud-top temperature (ctt)

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Nan Yang

New member
Dear WRF Users,

I am using wrf_user_getvar to calculate cloud top temperature (ctt) from WRF outputs.
I've checked the ncl source code wrf_fctt.f. The cloud-top temperature is calculated by interpolating the temperature to the level of unit optical depth (or a threshold) into the cloud, similar to RIP, but the absorption cross-section for cloud ice and cloud water are obtained from Dudhia (1989) in RIP, while in ncl:
ABSCOEFI = .272D0 ! cloud ice absorption coefficient in m^2/g
ABSCOEF = .145D0 ! cloud water absorption coefficient in m^2/g
I want to know why ctt is calculated this way, and where the constants come from.
Is there any reference paper for the ncl wrf_ctt calculation?