1. Clouds and radiation in a LSM L=50km

2. Physics@FOM, Veldhoven, 2009. 2 Stratocumulus cloud albedo: example cloud layer depth = 400 m effective cloud droplet radius= 10 m optical depth = 25 homogeneous stratocumulus cloud layer

3. Physics@FOM, Veldhoven, 2009. 3 Real clouds are inhomogeneous Stratocumulus albedo from satellite

4. Physics@FOM, Veldhoven, 2009. 4 Albedo for an inhomogeneous cloud layer Redistribute liquid water: optical depths = 5 and 45 inhomogeneous stratocumulus cloud layer mean albedo = 0.65 < 0.79

5. Physics@FOM, Veldhoven, 2009. Decrease optical thickness: Cahalan et al (1994): = 0.7 (FIRE I observations) 5 Cloud albedo in a weather forecast or climate model effective mean inhomogeneous albedo homogeneous albedo

6. Factor depends on the optical depth variance ( )

7. Analytical results for the inhomogeneity factor Assumption: Gaussian optical depth distribution not smaller than ~ 0.8 isolines

8. Environmental Physics 8 Scattering and absorption absorption cross section a : effective area of the molecule for removing energy from the incident beam shortwave longwave scattering cross section sca absorption cross section a