Evaluation of the Internal Variability in the Canadian Regional Climate Model over the Arctic domain using approach «Big-Brother Experiment»

Transcription

1 Evaluation of the Internal Variability in the Canadian Regional Climate Model over the Arctic domain using approach «Big-Brother Experiment» Maja Rapai! René Laprise Martin Leduc

2 Motivation: Plan of presentation! Arctic domain! Internal Variability (IV) in a RCM*! Effects of the domain size on the result Methodology:! «Big-Brother Experiment» (E) approach! Method of an ensemble of simulations Results:! Spatial correlation between LBs and *! Relative difference between mms* and! Taylor diagrams! Time evolution of the IV! Spatial distribution of the IV *RCM=Regional Climate Model RCM=Regional Climate Model LB=Little Brother =Big Brother mms=ensemble members

3 Sensitivity of simulations over Arctic on IC and LBC! Climate changes are very intensive over Arctic region! To be able to simulate those changes it is necessary to evaluate model s s errors over Arctic Rinke et al : Temperature at lowest level of the model! Evolution of RMSD* is independent of the magnitude, type or source of perturbation imposed in LBC or IC! A small perturbation in IC or LBC can cause an important divergence from the driving large-scale fields! RMSD is larger over Arctic than over the mid-latitudes domain of same size *RMSD=root mean square difference

4 Internal Variability of a RCM! IV is identified as a capacity of RCM to produce significant differences between two simulations slightly different only in their IC, for a given set of LBC! One way to evaluate IV is to calculate ensemble variance:! Another, to normalize ensemble variance with : TVAR = 1 T "(X # X ) 2 T i=1 Geopotentiel height at 500hPa! Spatial distribution of VI: EVAR t! Temporal evolution of VI: EVAR xy TVAR xy TVAR xy

5 Effect of the domain size! Large-scale! Transient-eddy component! Small-scale Leduc & Laprise, 2008

6 & LBs domains and the integration period Evaluation domain: Over the Arctic region characterized:! Important natural variability! Height topography (Greenland, ~4000 m) Validation period:! September and October! Year 1999: 1. It s s not the El Niño year 2. Sea-ice quantity is close to it s s mean value for this period of year 3. Recent year Objective:! Evaluation of the IV in Canadian Regional Climate Model (CRCM) over Arctic with respect to domain size *gp = grid points EZ=evaluation zone! CRCM, vs 3.6.1! 45 km, at 60 N! : 250x250 gp*! LBs: : gp gp EZ*: 74x74 gp! without spectral nudging

7 ! Methodology developed for testing one-way nesting technique in regional climate modeling with special attention on small scales (Denis et al., 2002) E F LB filter DCT =Big-brother F=Filtered LB=Little-brother Source: Leduc & Laprise (2008) Filter: km

8 Method of an ensemble of simulations estimation period LB1 August September October mm 1 mm 2 mm 3 n=20 ensemble members m=2 domains spin-up period mm n

9 Spatial correlation between LB et Kinetic energy at 925mb - stationary component R* = X * * mm X X *2 *2 mm X!LS!SS ms_8 ml_13 ms_12 ml_19 R*=98% R*=96% R*=95% R*=87% ms_3 ml_11 ms_2 ml_11 R*=97% R*=74% R*=93% R*=71%

10 Spatial correlation between LB et Kinetic energy at 925mb - transient-eddy component G * = X '2 mm '2 X!LS!SS ms_13 G*=98% ml_13 G*=123% ms_13 G*=103% ml_9 G*=138% R*=96% R*=88% R*=91% R*=87% ms_2 G*=104% ml_11 G*=64% ms_3 G*=100% ml_11 G*=169% R*=94% R*=67% R*=88% R*=66%

11 Relative difference between LB et Small-scale transient-eddy component! Mean sea level pressure D = 1 M M # m=1 X trans trans m " X trans X!Kinetic energy D=-9% D=2%! Precipitation rate!500mb D=-20% D=-4%!925mb D=-19% D=3% D=-11% D=2%

12 Taylor diagrams Small-scale stationary component! ke500! ke925! temp850! pcp

13 Taylor diagrams Small-scale transient-eddy component! ke500! ke925! temp850! pcp

14 Taylor diagrams Small-scale transient-eddy component! ke500! ke925 Correlation is smaller than in mid-latitudes! temp850! pcp

15 Internal variability in a RCM Temporal evolution! Temperature EVAR xy TVAR xy! LS! SS

16 Internal variability in a RCM Temporal evolution!kinetic energy! LS! SS

17 ! Precipitation Internal variability in a RCM Temporal evolution

18 Internal variability in a RCM Spatial distribution d of small-scale features! Kinetic energy! Precipitation EVAR t TVAR xy!500mb!925mb

19 Conclusion! Spatial and temporal correlations: increase with the decrease of the domain size smaller over Arctic that in mid-latitudes! Transient-eddy variance ratio: decreases with the reduction of the domain size! Deficit of the small-scale features over the smaller LB: spatial «spin-up» problem! IV of CRCM: IV of CRCM: larger intensity over the larger domain solution becomes free from LBC for some variables over the larger LB domain

20 Thank you! Questions??

21 Internal variability in a RCM Ensemble size experiment LB_ LB_

22 PHI th day of integration ml_1 ms_1

23 PHI th day of integration ml_2 ms_2

24 PHI th day of integration ml_3 ms_3

25 PHI th day of integration ml_4 ms_4

26 PHI th day of integration ml_5 ms_5

27 PHI th day of integration

28 Spatial correlation between LB et Precipitation rate - transient-eddy component!ls!ss ms_11 G*=69% ml_16 G*=145% ms_18 G*=71% ml_4 G*=170% R*=91% R*=86% R*=76% R*=72% ms_12 G*=68% ml_12 G*=140% ms_15 G*=75% ml_12 G*=176% R*=86% R*=55% R*=66% R*=58%

29 Spatial correlation between LB et Precipitation rate - stationary component!ls!ss ms_18 ml_16 ms_18 ml_3 R*=93% R*=96% R*=87% R*=79% ms_8 ml_11 ms_7 ml_2 R*=89% R*=78% R*=83% R*=65%

30 Spatial correlation between LB et Geopotential height at 850mb - transient-eddy component!ls!ss ms_2 G*=84% ml_14 G*=70% ms_18 G*=128% ml_19 G*=133% R*=99.3% R*=95.5% R*=72% R*=68% ms_8 G*=84% ml_5 G*=21% ms_3 G*=134% ml_17 G*=164% R*=98.6% R*=7.6% R* R*=66% R*=54%

31 Spatial correlation between LB et Geopotential height at 850mb - transient-eddy component!ls!ss ms_2 G*=84% ml_14 G*=70% ms_18 G*=128% ml_19 G*=133% «Intermittent R*=99.3% R*=95.5% R*=72% divergence in phase space»(von (von Storch R*=68% Storch,, 2005) ms_8 G*=84% ml_5 G*=21% ms_3 G*=134% ml_17 G*=164% R*=98.6% R*=7.6% R* R*=66% R*=54%