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Testing a new ice cloud effective radius parameterization in a regional climate model.

Testing a new ice cloud effective radius parameterization in a regional climate model. Gerd-Jan van Zadelhoff. 7 th ISTP, June 15 th 2006. Co-authors: E. van Meijgaard, D. P. Donovan, W. Knap, R. Boers. Overview. Why a new effective radius parameterization

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Testing a new ice cloud effective radius parameterization in a regional climate model.

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  1. Testing a new ice cloud effective radius parameterization in a regional climate model. Gerd-Jan van Zadelhoff 7th ISTP, June 15th 2006 Co-authors: E. van Meijgaard, D. P. Donovan, W. Knap, R. Boers 7th ISTP, Boulder

  2. Overview • Why a new effective radius parameterization • Description of the parameterization • Testing and comparing the parameterization • Including Reff in a regional climate model • Resulting differences • Conclusions 7th ISTP, Boulder

  3. Lidar signal 5 months Data 200 000 range/time points !! Radar Ze 0.99 0.9 R'eff 0.6 0.3 0.1 IWC'=IWC(R'eff/Reff) 35-GHz Radar, 532 nm Lidar Application to ARM data 7th ISTP, Boulder Jan 14, 2000

  4. Comparing microphysical ice cloud properties Comparison of results obtained over coastal Europe and Central U.S. Particle size vs. Temperature Cabauw ARM ARM Cabauw ARM Cabauw Size-vs-temperature relationship different for ARM-SGP and Cabauw ! (Chilbolton and Cabauw similar) Particle size vs. Depth into cloud 7th ISTP, Boulder

  5. Description of the parameterization Reff(Z,H)=A + B (Z/H) +C (Z/H)2 Z is the depth into cloud from cloud top H is the total cloud thickness 7th ISTP, Boulder

  6. Testing and comparing the parameterization 1 Use days with persistent ice clouds for radiative transfer. 7th ISTP, Boulder

  7. Testing and comparing the parameterization 2 For each measured radar profile the SW flux profile is calculated using different Reff parameterisations. 7th ISTP, Boulder

  8. Testing and comparing the parameterization 3 Reff (H,dZ) Reff =30 micron Reff (IWC,T) Histograms of differences between observations and calculations for 14 days. 7th ISTP, Boulder

  9. Including Reff in a regional climate model Observations Cabauw RACMO2 & ECMWF cy28 New parameterization ECMWF (cy30r1 91 levels) 7th ISTP, Boulder

  10. Regional results: Difference in W/m2 (Experimental-Control) 7th ISTP, Boulder

  11. The new parameterization results in a 2-3% difference in Transmission and planetary albedo for the entire RACMO2 region. • A direct comparison between observations and calculations can be performed using the radar profiles. • For a comparison of 14 persistent ice clouds without water clouds underneath the new parameterization shows a better comparison to observations compared to the other parameterizations. Conclusions…

  12. Regional results: normalized mean difference Transmissivity Reff (H,Z) Planetary albedo Reff (IWC,T) 7th ISTP, Boulder

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