Convective entrainment and large-scale organization of tropical precipitation: sensitivity of the CNRM-CM5 hierarchy of models

Transcription

1 Convective entrainment and large-cale organization of tropical precipitation: it ti enitivity of the CNRM-CM5 hierarchy of model Boutheina Ouelati & Gille Bellon CNRM, CNRS/Météo-France, Touloue, France

2 The double ITCZ yndrome JJAS mean precipitation GPCP CNRM-CM5: AMIP CNRM-CM5

3 The double ITCZ yndrome: CMIP5 v CMIP3 The Southern ITCZ index (SI), Bellucci et al Annual mean precipitation over the 20S-0, 100W-150W window ESM2G CM 3 LR MR HAD DGEM2-ES ES CanESM2 MP PI-ESM ESM-LR

4 The double ITCZ yndrome: Mechanim at play Role of atmophere-ocean feedback (Lin, 2007) Erroneou repreentation of SST ditribution in the tropical Pacific ocean, amplified by biae in coupled feedback Role of intrinic atmopheric procee (Schneider, 2002) SI: AMIP v CMIP

5 The double ITCZ yndrome: Mechanim at play The atmopheric procee controlling the ITCZ location: tate-of-the-art The CISK-baed mechanim (Charney, 1971; Holton et al., 1971; He et al., 1993; Walier and Sommerville, 1994) The Wind-Evaporation feedback (Numaguti, 1993) Competing role of frictional convergence and urface fluxe (Chao and Chen, 2004) Role of ABL temperature gradient in forcing the low-level convergence (Ouelati and Bellon, 2012) Role of cumulu parameterization Role of cumulu parameterization (Numaguti and Hayahi, 1991; Liu et al., 2009; Song and Zhang, 2009 )

6 The double ITCZ yndrome: Mechanim at play Role of cumulu parameterization Control via the vertical profile of convective heating (Ouelati and Bellon, 2012; Bacmeiter et al., 2006) Control via the modulation of moiture-convection feedback (Derbyhire et al., 2004; Del Genio, 2011)

7 The double ITCZ yndrome: Mechanim at play Role of cumulu parameterization Control via the vertical profile of convective heating (Ouelati and Bellon, 2012; Bacmeiter et al., 2006) Control via the modulation of moiture-convection feedback (Derbyhire et al., 2004; Del Genio, 2011) ( ) Explore the enitivity of the ITCZ to lateral entrainment in the CNRM-CM5 hierarchy of model CMIP AMIP (Terray, 1998 ; Chikira, 2010) Aquaplanet - Entrainment parameterization in the CNRM-CM5: - Senitivity tudie: 2 / 2 5 (CMIP) min( C z, z ABL )

8 Impact of entrainment on the double ITCZ JJAS mean precipitation GPCP 2 AMIP / 2

9 Impact of entrainment on the double ITCZ JJAS mean precipitation GPCP 2 AMIP 5 CMIP / 2 / 2

10 The SI index Impact of entrainment on the double ITCZ

11 Impact of entrainment on the double ITCZ Comparion with the aquaplanet model CMIP & AMIP: Zonal mean precipitation over central and eatern Pacific Aquaplanet: Zonal mean precipitation CMIP AMIP Aquaplanet

12 Impact of entrainment on the tropical circulation Diagnoing the circulation change by a regime-orting analyi (Bony et al., 2004) CMIP AMIP Aquaplanet More realitic PDF in AMIP 2 and CMIP 5 Decreaed frequency of weak-to-moderate acending regime Enhanced frequency of hallow convective regime / 2 A bimodal PDF in experiment

13 Mécanime à l origine du changement de circulation Impact of entrainment on the tropical circulation Undertanding di the PDF hape through h an energy bugdet analyi t p V. p V. Q Q Q 0 advh cond Q cond cond tur tur Q tur r r Q r 1 pp Note that: c pt gz A Q cond p dp A g 0 L P

14 Mécanime à l origine du changement de circulation Impact of entrainment on the tropical circulation Undertanding di the PDF hape through h an energy bugdet analyi t p p V. Q Q Q 0 advh cond V. Q cond cond tur tur Q tur r r Q r 1 p Note that: c pt gz A Q cond p dp A g 0 L P AMIP Aquaplanet

15 Impact of entrainment on the tropical circulation Undertanding di the PDF hape through h an energy bugdet analyi advh cond tur r 2 / 2 AMIP Aquaplanet The bimodality of the PDF reult from the bimodality of cond The hape of the PDF reult from the interaction between Large-cale circulation and Precipitation

16 Mécanime Impact of à entrainment l origine du on changement the tropical de circulation Convective v Stratiform contribution cond condc conds, with condc conds L PC p L PS pp 2 / 2 AMIP Aquaplanet cond The bimodality of reult from the bimodality of condc

17 Impact of entrainment on the tropical circulation Relationhip between precipitation it ti and large-cale l circulation 2 AMIP Aquaplanet / hPa / day & : hPa / day Overetimated Total P compared to OBS > 2 / 2 Total P in Total P in The PDF et the double ITCZ bia : Different Pc-P partitioning in 2 and / 2

18 Impact of entrainment on the tropical circulation Relationhip between precipitation it ti and large-cale l circulation AMIP Aquaplanet 2 A more realitic repreentation ti of weak-to-moderate t acending regime An overetimation of the contribution of trong acending regime and ubiding regime to precipitation

19 Concluion The enitivity of the ITCZ tructure to entrainment i robut acro the hierarchy of model The double ITCZ i aociated with: - A bimodal PDF reulting from feedback from large-cale circulation and convective precipitation An enhanced entrainment rate alleviate thi bia - An error in precipitation magnitude under trong acending regime and ubiding regime Ocean-Atmophere GCM v Atmophere-only GCM Convection inhibition through entrainment need to be tronger in the coupled model to counteract the amplifying effect of coupled procee on the double ITCZ

20 Thank you for your attention