The horizontal diffusion issue in CRM simulations of moist convection

Transcription

1 The horizontal diffusion issue in CRM simulations of moist convection Wolfgang Langhans Institute for Atmospheric and Climate Science, ETH Zurich June 9, 2009 Wolfgang Langhans Group retreat/bergell June 9, / 25

2 Outline 1 Introduction and Motivation 2 Objectives 3 Preliminary results 4 Preliminary conclusions Wolfgang Langhans Group retreat/bergell June 9, / 25

3 Introduction and Motivation Wolfgang Langhans Group retreat/bergell June 9, / 25

4 Modeling the European summer climate Indeed, differences in parameterizations between RCMs appear more important than differences in synoptic climatology between AGCMs... Vidale et al. (2007) Wolfgang Langhans Group retreat/bergell June 9, / 25

5 Modeling the European summer climate The prominent role of physical parameterizations (e.g., convection, land-surface atmosphere exchange, radiation, and clouds) may explain the large model spread in summer... Frei et al. (2006) Wolfgang Langhans Group retreat/bergell June 9, / 25

6 Sensitivity to convection parameterizations Soil moisture-precipitation feedback Hohenegger et al. (accepted) Wolfgang Langhans Group retreat/bergell June 9, / 25

7 Cloud-resolving modeling {z } x 100 km = {z} x 1 km Wolfgang Langhans Group retreat/bergell June 9, / 25

8 Objectives & scientific questions Wolfgang Langhans Group retreat/bergell June 9, / 25

9 Goals The overarching goals of this PhD project are A to develop a cloud-resolving regional climate modeling capability, and How is the predicted convective preciptiation related to model components? What is the impact of horizontal resolution? B to advance our knowledge about physical climate feedbacks and improving climate scenarios. How do mountain circulations interact with the diurnal cycle of moist convection? Wolfgang Langhans Group retreat/bergell June 9, / 25

10 Preliminary results Wolfgang Langhans Group retreat/bergell June 9, / 25

11 Model setup Version: CLM 4.3 Dynamics: 3rd order RK scheme (Wicker and Skamarock 1998, 2002) 5th order advection, pos. definite qx advection Physics: prognostic TKE-based turbulence scheme no cumulus scheme graupel scheme TERRA_ML Topographic correction scheme for radiation Large Alpine domain: gridpoints dϕ = dλ = 0.02, dt = 30 s Wolfgang Langhans Group retreat/bergell June 9, / 25

12 Sensitivity to horizontal diffusion Given as M HD = α 2 ( 2 ψ), ψ = u, v, w, q v, q c, q i, t, p Wolfgang Langhans Group retreat/bergell June 9, / 25

13 Sensitivity to horizontal diffusion Given as M HD = α 2 ( 2 ψ), ψ = u, v, w, q v, q c, q i, t, p Wolfgang Langhans Group retreat/bergell June 9, / 25

14 Sensitivity to horizontal diffusion Given as M HD = α 2 ( 2 ψ), ψ = u, v, w, q v, q c, q i, t, p Wolfgang Langhans Group retreat/bergell June 9, / 25

15 Small-scale fluctuations Vertical velocity at 5 km MSL DIFFUSED UNDIFFUSED Wolfgang Langhans Group retreat/bergell June 9, / 25

16 Power spectra of vertical velocity a.m. p.m UTC B22A B22DIFFMASK UTC B22A B22DIFFMASK variance (m 3 /s 2 ) variance (m 3 /s 2 ) wavelength n x 10 0 wavelength n x 10 0 Wolfgang Langhans Group retreat/bergell June 9, / 25

17 Power spectra of vertical velocity a.m. p.m. variance (m 3 /s 2 ) UTC B22A B22DIFFMASK variance (m 3 /s 2 ) UTC B22A B22DIFFMASK = wavelength n x 10 0 wavelength n x 10 0 Wolfgang Langhans Group retreat/bergell June 9, / 25

18 Power spectra of vertical velocity a.m. p.m. variance (m 3 /s 2 ) UTC B22A B22DIFFMASK variance (m 3 /s 2 ) UTC B22A B22DIFFMASK = wavelength n x 10 0 wavelength n x UTC B22A B22DIFFMASK UTC variance (m 3 /s 2 ) variance (m 3 /s 2 ) 10 4 B22A B22DIFFMASK wavelength n x 10 0 wavelength n x 10 0 Wolfgang Langhans Group retreat/bergell June 9, / 25

19 Power spectra of vertical velocity a.m. p.m. variance (m 3 /s 2 ) UTC B22A B22DIFFMASK variance (m 3 /s 2 ) UTC B22A B22DIFFMASK = wavelength n x 10 0 wavelength n x 10 0 variance (m 3 /s 2 ) UTC B22A B22DIFFMASK variance (m 3 /s 2 ) UTC = B22A B22DIFFMASK wavelength n x 10 0 wavelength n x 10 0 Wolfgang Langhans Group retreat/bergell June 9, / 25

20 Numerical stability u-velocity at 1.3 km above ground DIFFUSED UNDIFFUSED = Adria Wolfgang Langhans Group retreat/bergell June 9, / 25

21 Mean diurnal cycle of hydrometeors DIFFUSED UNDIFFUSED CLOUD WATER CLOUD WATER RAIN RAIN GRAUPEL GRAUPEL Wolfgang Langhans Group retreat/bergell June 9, / 25

22 Heat budget DIFFUSED total UNDIFFUSED latent heating Wolfgang Langhans Group retreat/bergell June 9, / 25

23 Example: Vertical cross-section 12 UTC 12 July 2006, southern Alpine rim Potential temperature Latent heating W E W E Wolfgang Langhans Group retreat/bergell June 9, / 25

24 Heat budget Turbulent flux divergence DIFFUSED UNDIFFUSED Radiative flux divergence Wolfgang Langhans Group retreat/bergell June 9, / 25

25 Example: Vertical cross-section 12 UTC 12 July 2006, southern Alpine rim Turbulence Radiation * 10 W E W E Wolfgang Langhans Group retreat/bergell June 9, / 25

26 Heat budget DIFFUSED 3D advection UNDIFFUSED Vertical advection Wolfgang Langhans Group retreat/bergell June 9, / 25

27 Example: Vertical cross-section 12 UTC 12 July 2006, southern Alpine rim 3D advection Vertical advection W E W E Wolfgang Langhans Group retreat/bergell June 9, / 25

28 Preliminary conclusions Wolfgang Langhans Group retreat/bergell June 9, / 25

29 Preliminary conclusions First simulations of a convective period in July 2006 have been conducted. Wolfgang Langhans Group retreat/bergell June 9, / 25

30 Preliminary conclusions First simulations of a convective period in July 2006 have been conducted. A budget analysis tool for potential temperature and moisture scalars has been implemented into COSMO. Wolfgang Langhans Group retreat/bergell June 9, / 25

31 Preliminary conclusions First simulations of a convective period in July 2006 have been conducted. A budget analysis tool for potential temperature and moisture scalars has been implemented into COSMO. The amount of convective precipitation is related to computational horizontal diffusion. stronger diffusion less convective precipitation t diffusion most influential Affects averaged heat and moisture budgets Optimum setup: q0.0, t 0.0, u= (G. Zängl) Wolfgang Langhans Group retreat/bergell June 9, / 25

32 Thanks for your attention! Wolfgang Langhans Group retreat/bergell June 9, / 25