1. Cloud liquid water and ice content by multi-wavelength radar
Nicolas Gaussiat Henri Sauvageot
Anthony J. Illingworth

2. Dual-Wavelength measurements
For a dual-wavelength pair ( Long, Short) :
DWR is due to (1) differential attenuation , (2) Mie scattering :
In clouds, Mie scattering is more often due to ice. Differential attenuation is dominated by liquid water :
A 95 – 35 = 8 dB km-1/g m-3
A 35 – 3 = 2 dB km-1/g m-3

3. F[dB] Assuming a gamma distribution of scatterers :
the Mie scattering term (F) is a function of D0 : 25
F3-95 20
F35-95
F[dB] 15 10
F3-35 5

4. ARM case study (1) Cirrus : (2) Stratocumulus : (3) Mixed phase cloud:
Excepted in cirrus, LWC content derive from differential attenuation ignoring Mie scattering looks good, BUT…

5. Simulating differential attenuation

6. Principle of a triple–wavelength method
With 3 frequencies 3, 35, 95 GHz :
k ~ 0.2
and
The system is solved using an iterative process :
First guess DWR3-35 Mie scattering only  D0 first estimate
With D0 ,Mie scattering term F3-94 is predicted
(Observed DWR3-94 – predicted F3,94)  Ad3-94 attenuation profile.
With Ad3-94  correction First guess : DWR3-35 is now corrected for attenuation
When Ad and F profiles are stables LWC is derived from Ad3-94
(Ad94 – 3 = 10 dB km-1/g m-3 )

7. Running triple-wavelength method

8. Using triple-wavelength method in mixed phase clouds

9. Dual-wavelength observables

10. Merging Mie scattering and attenuation

11. Microphysical
Parameters
Derived
From
Ad and F