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1. Designing unified convection parameterizations: two proposals related to equation sets and entrainment. Jean-Marcel Piriou, Météo-France. GCSS / RICO Workshop, New-York 18-21 September 2006. Garde

2. Introduction: motivation for designing unified convective schemes Several operational and research models operated PHYSICS Global ARPEGE Aquaplanet mode SCM ARPEGE (EUROCS, GATE, TOGA,BOMEX, ARM, RICO, …) Global regular ARPEGE / 4DVAR-ass./ 56 km LAM ALADIN / 3DVAR / 10 km CSRM AROME / 3DVAR / 2.5 km Global stretched ARPEGE / 4DVAR-ass./ 23 to 133 km

3. Introduction: motivation for designing unified convective schemes Sharing parameterizations between models: • Simpler to manage a single set of source codes. • Feedback from cases studies, scores, users  modifications  improve also the other models. • Sharing a simple and general concept  better understanding of convection.

4. Summary 2 examples of on-going efforts in designing unified convective parameterizations: • Separating microphysics and transport in grid-scale equations. Fit wider range of grid sizes (GCM - LAM - CSRM). • Link between cold pools and entrainment.  Fit a wider range of processes (shallow NP – shallow P - deep conv.).A contribution for RICO observations and LES simulations? • Conclusions.

5. Fin • Part 1: A convective scheme using separate microphysics and transport terms in grid-scale equations

6. MTCS (Microphysics and Transport Convective Scheme) Separating microphysics and transport in grid-scale convective equations Buoyant convective condensation Unbuoyant convective condens. (overs.) Cloudy evaporation Precipitation evaporation SH précip., melt. Transport MTCS: MT-CS M & T coupled: (Q1c: réchauffement convectif, Q2c: assèchement convectif fois L) Transport Net condensation

7. MTCS (Microphysics and Transport Convective Scheme) Mass flux / vertical velocity in the SGS convectif updraft MTCS: Vertical integral of buoyancy Top LNB P & NH effects Siebesma et al. (2003) Taking into account the overshoots.

8. MTCS (Microphysics and Transport Convective Scheme) MTCS: Consequences: • Grid-scale equations of the SGS convective scheme are closer to those of CSRM or LES. • Can share microphysical modules between CSRM and parameterization (not done so far). • Validation of the parameterization versus CSRM or LES can be done for each of the above terms. • No need to assume a stationnarized cloud budget  more consistent with a future prognostic equation of cloud fraction.

9. MTCS (Microphysics and Transport Convective Scheme) What has been done so far MTCS: First prototype with • Deliberately crude microphysics (simple condensation scheme, autoconversion/collection, diagnostic q_r q_s, Kessler-type evaporation) • New proposal for entrainment…

10. Fin • Part 2: Cold pools and entrainment

11. Cold pools and entrainment Context: EUROCS/GCSS diurnal cycle of deep convection over land Q1 ARPEGE oper Q1 CSRM MNH local solar time local solar time Q1 (K/day): apparent heat source ARPEGE V1 ARPEGE V1 + entr. historique

12. Cold pools and entrainment Context: EUROCS/GCSS diurnal cycle of deep convection over land Q2 ARPEGE oper Q2 CSRM MNH local solar time local solar time Q2 (K/day): apparent moisture sink ARPEGE V1 ARPEGE V1 + entr. historique

13. Cold pools and entrainment A schematic view from CSRM animations Shallow cumulus phase High entrainment:

14. Cold pools and entrainment Precipitating cumulus phase Intermediate entrainment:

15. Cold pools and entrainment Deep convection phase Low entrainment:

16. Cold pools and entrainment Entrainment: an heuristic proposal: prognostic link evap. prec.  entr. Entrainment epsilon depends on local pressure and on zeta, probability of undiluted ascents at the current level Zeta’s source is precipitation evaporation, zeta’s sink is a linear relaxation to zero.

17. Cold pools and entrainment Results on the EUROCS diurnal cycle of deep conv. over land Q1 ARPEGE oper Q1 CSRM MNH ARPEGE V1 Q1 ARPEGE historical entr.

18. Cold pools and entrainment Results on the EUROCS diurnal cycle of deep conv. over land Q2 ARPEGE oper Q2 CSRM MNH ARPEGE V1 Q2 ARPEGE historical entr.

19. Cold pools and entrainment Results on the EUROCS diurnal cycle of deep conv. over land • The new approach, a scheme based on separate microphysics and transport scheme, works: GATE, TOGA-COARE, EUROCS sensitivity to humidity, EUROCS diurnal cycle of deep convection over land. • Relating prognostically the entrainment to precipitation evaporation improves dramatically the predicted diurnal cycle of convection. (1D, 3D under progress). • It also allows to use the same convective scheme for shallow and deep convection. • Piriou et al. 2006, submitted to JAS. ARPEGE V1

20. Image: source Larry Di Girolamo, GCSS Workshop New-York, 2006 • Larry Di Girolamo, about RICO: • « Lines along cold pools: 90% of the time. » • « Precipitation is strongly tied to mesoscale organization, especially along cold pools. » • « Clouds between ~ 3 to 4 km contribute the most to the total rain rates. » • Transition from shallow NP  shallow P  congestus  deep: a collective effect of several drafts. • Studying this collective effect cannot be done through local PDFs nor global PDFs  a new way of investigating RICO observations and LES simulations required?

21. Fin • Conclusions

22. Conclusions • MTCS proposal: separating Microphysics and Transport in Convective Schemes. • Varying entrainment rates, depending on cold pools dynamics. May be parameterized in a quantitative and energy conserving form. • Piriou et al. 2006, submitted to JAS. • GCSS / RICO: making studies (observations, LES simulations) to quantify convective transition as a collective effect of several clouds, through cold pools?