Impact of the Barrier Layer on the variability of the Southeastern Arabian sea

Transcription

1 Impact of the Barrier Layer on the variability of the Southeastern Arabian sea Masson S., J.-J. Luo, T. Yamagata, Frontier Research Center for global Change, JAMSTEC EU collaborators (France-Germany-Italy)

2 Precipitation monsoon onset Introduction: Seasonal variability of the southeastern Arabian Sea BLT (m) box=[6,77,6,15] Model (21-12) Model estimate Levitus estimate Spring SST warming 31 3 Barrier Layer SST 29 2 Model (21-12) Levitus TMI (199-2[3]) Reynolds (192-22) Rao and Sivakumar, 1999 Shenoi et al., 1999 Durand et al., 2 Precip (mm/d) Model (21-12) CMAP ( ) TMI (199-2[3]) Explore and quantify this hypothesis with a coupled model

3 The SINTEX-Frontier CGCM 1. Model components: No flux correction AGCM (MPI, Germany): ECHAM (T16L19) OGCM (LODYC, France): OPA (ORCA2: 2 x.5 ~2, L31) Coupler (CERFACS, France): OASIS2 2. European collaborators: LODYC: OPA group INGV (Italy): Antonio Navarra s group MPI: ECHAM model group CERFACS: OASIS coupler group PRISM project group 3. Reference experiment: we keep 1 years from 21 to 12

4 Monsoon onset in the SE Arabian Sea 2 2N Model CMAP TMI REF: Precip, May REF: CMAP ( ) Precip, May 2 2 May 2N May May 2N TMI (199-2) Precip, May N 1S 2 2N 1 1N 5E 6E 7E E 9E 1E (mm/day): Min=.1, Max= 1.1, Int= 2. 1N 1S 1 1N 5E 6E 7E E 9E 1E (mm/day): Min=., Max= 1.17, Int= 2. REF: Precip, June REF: CMAP ( ) Precip, June 2 2 June 2N June 2N June N 1S 1 1N 5E 6E 7E E 9E 1E (mm/day): Min=., Max= 6., Int= 2. TMI (199-2) Precip, June 1S 2 2N 5E 6E 7E E 9E 1E (mm/day): Min=., Max= 26.51, Int= 2. 1S 5E 6E 7E E 9E 1E (mm/day): Min=.1, Max= 2.2, Int= 2. REF: Precip, July REF: CMAP ( ) Precip, July 2 2 July July July 2N 2N 16 1S 5E 6E 7E E 9E 1E (mm/day): Min=., Max= 132., Int= 2. TMI (199-2) Precip, July N 1S 5E 6E 7E E 9E 1E (mm/day): Min=., Max= 25.7, Int= 2. 1N 1S 5E 6E 7E E 9E 1E (mm/day): Min=.1, Max= 21.92, Int= N 1S 5E 6E 7E E 9E 1E (mm/day): Min=., Max= 136., Int=

5 3. Spring variability of the SST: mini-warm pool formation Joseph, 199 Rao and Sivakumar, N 1 1N REF (clim yr 21-12), SST, February E 5E 55E 6E 65E 7E 75E E (C): Min= 2.1, Max= 29.32, Int= N 1 1N REF (clim yr 21-12), SST, March E 5E 55E 6E 65E 7E 75E E (C): Min= 2.65, Max= 3.26, Int= N 1 1N REF (clim yr 21-12), SST, April E 5E 55E 6E 65E 7E 75E E (C): Min= 26.7, Max= 31.26, Int= N 1 1N Feb Mar Apr May REF (clim yr 21-12), SST, May N 1 1N Lev, SST, February E 5E 55E 6E 65E 7E 75E E (C): Min= 23.5, Max= 31.5, Int= N 1 1N Lev, SST, March E 5E 55E 6E 65E 7E 75E E (C): Min= 25.5, Max= 31.5, Int= N 1 1N Lev, SST, April E 5E 55E 6E 65E 7E 75E E (C): Min= 27.5, Max= 32.25, Int= N 1 1N Feb Mar Apr May Lev, SST, May E 5E 55E 6E 65E 7E 75E E (C): Min= 27.35, Max= 31.19, Int= N 1 1N Jun 29. REF (clim yr 21-12), SST, June E 5E 55E 6E 65E 7E 75E E (C): Min= 27.5, Max= 31.95, Int= N 1 1N Jun Lev, SST, June E 5E 55E 6E 65E 7E 75E E (C): Min= 26.92, Max= 31.92, Int=.25 5E 5E 55E 6E 65E 7E 75E E (C): Min= 21.6, Max= 33., Int=

6 Seasonal Variability : OK Model Bias : ~1 C 31 May Temperature, box=[6,77,6,15] Spring warming : Feb May OK 3 sosstsst 29 2 Model REF Levitus TMI (199-2[3]) AVHRR-NSIPP ( ) Aug

7 How to explain the spring warming? 1) heat fluxes Shenoi et al Sengupta et al. 22 Problems: early SST warming late SST decrease Sun ML BL 2) Barrier layer Shenoi et al Durand et al. 2 Less Solar heat flux Smaller thermal inertia weak or positive entrainment

8 2 2N BLT % temp inv. Men temp inv. REF (clim yr 21-12), BLT, uary 2 2N REF (clim yr 21-12), % Temp Inv, uary 2 2N REF (clim yr 21-12), Temp Inv Mean, uary N 3 1N 1N E 5E 55E 6E 65E 7E 75E E (m): Min=., Max= 39.72, Int= 5. 5E 5E 55E 6E 65E 7E 75E E (m): Min=., Max= 96.17, Int= 1. 5E 5E 55E 6E 65E 7E 75E E (m): Min=., Max=.75, Int= N REF (clim yr 21-12), BLT, February REF (clim yr 21-12), % Temp Inv, February REF (clim yr 21-12), Temp Inv Mean, February 2 2 Feb Feb Feb 2N 2N N 1N 2 1N E 5E 55E 6E 65E 7E 75E E (m): Min=., Max= 5.35, Int= 5. 5E 5E 55E 6E 65E 7E 75E E (m): Min=., Max= 7., Int= 1. 5E 5E 55E 6E 65E 7E 75E E (m): Min=., Max=.6, Int=

9 BL formation mechanism 1) Downwelling Bruce 199, 199 Shankar et Shetye 1997 Depth (m) Levitus Temperature Levitus, Temperature Depth (m) Levitus Salinity Levitus, Salinity (PSU): Min= 13.73, Max= 3.2, Int=.5 Model Temperature Clim ORCA5 yr 21, Temperature 2 (PSU): Min= 3.1, Max= 36.11, Int=.1 Model Clim ORCA5 yr Salinity 21, Salinity 2) Imput of fresh water Shetye et al Rao et Sivakumar 23 Depth (m) Depth (m) (m): Min= 1.31, Max= 29.2, Int=.5 (m): Min= 3.19, Max= 35.9, Int=

10 A perturbation experiment Suppress, in the SE Arabian Sea, the salt impact on the vertical stratification which controls the depth of the mixed layer Reference (yr 21 12) : with active salinity in the vertical stratification Perturbation (yr 21 12) : without active salinity in the vertical stratification

11 REF - PERTURB yr N 2N 1N Mar, SST. REF-PERTURB, SST, March.2.. 3N 2N 1N Mar, Precip REF-PERTURB: Precip, March REF: +.6 C in Apr REF: +3mm/d in May 1S 3N 2N 1N. 5E 6E 7E E 9E 1E (C): Min= -.21, Max=.2, Int=.1. REF-PERTURB, SST, April.2. 1S 5E 6E 7E E 9E 1E (C): Min= -.1, Max=.6, Int=.1 3N 2N Apr, SST May, SST REF-PERTURB, SST, May. 1S 3N 2N 1N 1S 3N 2N 5E 6E 7E E 9E 1E 2 (mm/d): Min= -1.76, Max= 1.35, Int= 1. Apr, Precip REF-PERTURB: Precip, April 5E 6E 7E E 9E 1E 2 (mm/d): Min= -1.97, Max= 1.1, Int= 1. May, Precip REF-PERTURB: Precip, May 1N 1S 3N 2N. 5E 6E 7E E 9E 1E (C): Min= -.2, Max=.39, Int=.1 REF-PERTURB, SST, June Jun, SST 1N 1S 3N 2N -2 5E 6E 7E E 9E 1E 2 (mm/d): Min= -3.3, Max= 1.2, Int= 1. REF-PERTURB: Precip, June Jun, Precip 1N 1S... 5E 6E 7E E 9E 1E (C): Min= -.3, Max=.16, Int=.1 1N 1S 5E 6E 7E E 9E 1E 2 (mm/d): Min= -1.92, Max= 1.59, Int=

12 SST: REF (solid) and PERTURB (dashed) REF: Warmer in April More precipitation from April to July C C Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Feb Mar SST: REF - PERTURB -.1 Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Feb Mar REF: earlier monsoon onset (15 days) mm/d Precipitation: REF (solid) and PERTURB (dashed) Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Feb Mar Precipitation: REF - PERTURB mm/d 1-1 Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Feb Mar

13 Conclusion Significant impact of the Barrier Layer in the SE Arabian Sea +.6 C in Apr +3mm/d in May earlier monsoon onset (15 days ) Remaining Questions Impact of the Ocean resolution better ocean circulation in the SouthEast Arabian Sea thinner salinity stratification Impact on the onset of the monsoon => interannual variability