1. Testing a new ice parameterization scheme based on CloudNET & ARM observations. CloudNet Final meeting: October 2005 Gerd-Jan van Zadelhoff Co-authors: Dave Donovan, Erik van Meijgaard

2. KNMI October 27, 2004 April 18, 1996, CLARA

3. ARM Cabauw ARM Particle size vs. Temperature Doppler Velocity vs. Particle size Size-vs-temperature relationship different for ARM-SGP and Cabauw ! (Chilbolton and Cabauw similar ) Size-vs-Fall speed similar between ARM-SGP and Cabauw Comparison of results obtained over coastal Europe and Central U.S. Comparing microphysical ice cloud properties

4. Cabauw ARM Particle size to cloud depth from cloud-top R’ eff –vs-distance from cloud-top [R’ eff (  z)] - R’ eff (T)  ARM-SGP & Cabauw results are different - R’ eff (  Z)  ARM-SGP & Cabauw results are similar (|  Z| < 3 km) ARM H> 4.5 km 3.0 < H < 4.5 km 1.5 < H < 3.0 km H < 1.5 km

5. Comparing mean profiles to normalized cloud thickness ARM Cabauw - R eff (  Z, complex polycrystals)  ARM-SGP & Cabauw results are the same within the errors.

6. R eff =A+B(  Z/H)+C(  Z/H) 2 ARM Parameterization of R eff versus cloud thickness - R eff (  Z, complex polycrystals): Use parabolic fits to the observed values A=A 0 +A 1. H B=B 0 +B 1. H C=C 0 +C 1. H

7. Current Reff(T) relationship in Racmo vs. Obs Mean R eff -T relationship observed, using Complex polycrystals as habit. Current Racmo parameterization

8. Reff parameterization & distribution. Reff parameterization & distribution. Resulting distribution (left) of the new R eff parameterizations based on cloud- thickness.

9. Differences due to changes in parameterization Differences in the mean net short wave flux at the surface and cloud cover. Comparing the new parameterization with the current operational one. Hindcast run (1995) Climate run (1995)

10. Differences due to changes in parameterization Differences in the mean net short wave flux at the surface and cloud cover. Comparing the new parameterization with the current operational one. Hindcast run (1995) Climate run (1995)

11. Conclusions New parameterization gives back both the mean Reff-T relationship and its distribution. There is no temperature dependent input needed. Current vertical resolution RACMO too large for thinnest clouds. Monthly mean (day + night) planetary albedo changes by up to 4 % in the hindcast case due to smaller ice particles. Combination of both IWC and Reff has to change in RACMO to give observed SW fluxes. Comparison of R eff (  H) has to be confirmed using all three CloudNET, the ARM SGP, TWP and NSA sites.