Spectral microphysics in weather forecast models with special emphasis on cloud droplet nucleation Verena Grützun, Oswald Knoth, Martin Simmel, Ralf Wolke IfT Leipzig Oct. 24 th 2006

2 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006Motivation Influence of aerosols not included. (Maritim/continental, precipitation suppression by pollution, …) Example: Pollution tracks over Australia and Asia ( D. Rosenfeld, 2000) 1: Istanbul 2: Izmit 3: Bursa 5: Port Augusta power plant 6: Port Pirie lead smelter 7: Adelaide port 8: Oil rafineries

3 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006Introduction “Spectral microphysics in weather forecast models” Goals: Introduction of a spectral microphysics into the Lokalmodell of the German Weather Service. Investigation of the the influence of aerosols (composition, size distribution, number concentration) on precipitation Improving quantitative precipitation forecast through offering new approaches to microphysical parameterizations Status: …

4 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006Introduction Implementation of a SPECtral microphysicS (warm and mixed phase) into LM (“LM-SPECS“) Implementation of conservative advection scheme for moisture variables Test cases of cloud evolution (Heat bubble, 2D mountain overflow) Simplified description of CCN evolution in progress Comparison with two moment microphysical scheme “Spectral microphysics in weather forecast models” Work to date:

5 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006Theory Model system LM-SPECS I  t LM dynamics microphysics t LM k t LM k+1 m  t mp …… t mp 1 t mp m t mp i (=t LM k ) (=t LM k+1 ) T, q c, q v u,v,w, p, , T T(t LM k )+i  t mp  T dyn p(t LM k )+i  t mp  p dyn  (t LM k )+i  t mp  dyn Advection u,v,w,p,T Advection q v, n bin, q c bin, q a bin, q s bin

6 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006Theory Model system LM-SPECS II Combined spectrum of CCN and droplets in (currently) 66 mass-doubling bins Spherical ice particles in (currently) 66 bins Number density, total water mass, (frozen water mass,) total aerosol mass, soluble aerosol mass (binwise) Purely insoluble particles as ice nuclei Condensation, collision, break-up, contact / immersion / deposition freezing, secondary freezing processes

7 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Test case: Heat bubble Setup Model domain 80 km x 80 km Horizontal resolution 1 km, 40 vertical layers Initial wind equal zero Temperature disturbance of up to 2 K (“Heat bubble“ at the height of 1.4 km, hor. radius 10 km) Sensitivity study w. resp. to initial number distribution N T : Artificial test case: N T = 200 cm -3 (N200) N T = 566 cm -3 (N566) N T = 4000 cm -3 (N4000)

8 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: Heat bubble at 24 min Liquid water content N566

9 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: Heat bubble at 24 min Particles and relative humidity

10 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: Heat bubble at 24 min Particle spectra 6.4 km 3.7 km 2.9 km

11 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: Heat bubble at 24 min Accumulated rain

12 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: Cloud ice First look on mixed phase clouds

13 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Test case: 2D Mountain Setup 2-dimensional mountain overflow, 400 gridpoints in x- direction Horizontal resolution 2.8 km, 38 vertical layers Horizontal wind at start:15 m/s Idealized vertical sounding (Thompson et al., 2004) Warm-phase microphysics Sensitivity study w. resp. to mountain height, comparison with 2-moment bulk microphysics scheme Artificial test case:

14 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: 2D mountain at 6h Liquid water content Height: 500 m polluted clean

15 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: 2D mountain at 6h Liquid water content Clean case 1000m 500m

16 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: 2D mountain at 6h Liquid water content Clean case A. Mühlbauer et al., m comparison with 2-mom. scheme

17 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: 2D mountain at 6h Liquid water content Polluted – clean A. Mühlbauer et al., m comparison with 2-mom. scheme

18 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Results: 2D mountain at 6h Precipitation – spatial distribution A. Mühlbauer et al., 2006 Spectral microphysics comparison with 2-mom. scheme

19 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006Summary The model system LM-SPECS has been developed, coupling the LM with a spectral microphysics scheme Sensitivity studies on an artificial heat bubble were done to test the model performance, results: Spectral information about the development from humid aerosol particles to rain drops; depletion, supersaturation Strong influence of particle number on accumulated rain: more particles  less & later rain 2D Mountain test case: Sensitivity study on mountain height, comparison with 2-moment-bulk scheme. Quantitatively similar results, but differences in cloud structure and resulting distribution of rain

20 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006OutlookOutlook Second project phase Improving the mixed phase microphysics Aiming for realistic episodes, e.g. -Boundary conditions, model nesting Further comparison with two-moment microphysics, esp. mixed phase microphysics Improving the numerics & further improvement of realistic runs Perspective: Case studies with the help of COPS data

21 Verena Grützun, IfT, Modelling Department, Oct. 24 th 2006 Thank you for your attention!