xi general cosmo meeting offenbach,7-10 september 2009

A.Montani; The COSMO-LEPS system: present status and outlookCOSMO meeting, Offenbach, 7-11 September 2009

Clustering of multi-model global ensembles

for dynamical downscaling purposes:

first steps

Andrea Corigliano, Andrea Montani

ARPA-SIMC

Hydrometeorological Service of Emilia-Romagna, Bologna, Italy

XI General COSMO meetingOffenbach,7-10 September 2009


Outline

• Description of the work• Present status• Future plans


Dim 2

Initial conditions Dim 1 Dim 2

Possible evolution scenarios

Dim 1 Initial conditions

ensemble size reduction

Cluster members chosen as representative members (RMs)

LAM integrations driven byRMs

LAM scenario

LAM scenario

LAM scenario

COSMO-LEPS methodologyCOSMO-LEPS methodology


COSMO-LEPS suite @ ECMWF: present status

d-1d-1 dd d+5d+5d+1d+1 d+2d+2 d+4d+4d+3d+3

older EPSolder EPS

younger EPSyounger EPS

clustering clustering periodperiod

0000

1212

Cluster Analysis and RM identificationCluster Analysis and RM identification

4 variables4 variables

Z U V QZ U V Q

3 levels3 levels

500 700 850 hPa500 700 850 hPa

2 2 time time stepssteps


European European areaarea

Complete Complete LinkageLinkage

1616 Representative Representative Members driving the Members driving the 1616

COSMO-model COSMO-model integrations (weighted integrations (weighted according to the cluster according to the cluster

populations)populations)

employing either employing either Tiedtke or Kain-Fristch Tiedtke or Kain-Fristch

convection scheme convection scheme (randomly choosen) (randomly choosen)

++perturbations in perturbations in

turbulence schemeturbulence scheme

COSMO-LEPS

clustering area

• suite runs as a “time-critical application” managed by ARPA-SIMC;

• Δx ~ 10 km; 40 ML; fc+132h;• COSM0 v4.7 since Feb09

(with Runge-Kutta + multi-layer soil scheme);

• computer time (6.0 million BU for 2009) provided by the COSMO partners which are ECMWF member states.

COSMO-LEPS

Integration Domain


Multi-model clustering: first approach

d-1d-1 dd d+5d+5d+1d+1 d+2d+2 d+4d+4d+3d+3

UKMO MOGREPS

ECMWF EPS

clustering clustering timetime

1212


1 variable1 variable

ZZ

1 level1 level

500 hPa500 hPa

1 1 time time stepstep




1616 Representative Representative Members are selectedMembers are selected

COSMO-LEPS

clustering area

COSMO-LEPS

Integration Domain


Possible evolution scenarios

initial conditions by EPS

Methodology

initial conditions by MOGREPS

Consider both ECMWF EPS and UKMO MOGREPS and study properties of cluster analysis on multi-ensemble:

How many times do the 2 ensembles mix? Where do the RMs come from? How to they score depending on their “origin”? BEFORE DOWNSCSALING: is there added value with respect to single-model

ensemble? AFTER DOWNSCALING: is there added value with respect to single-model ensemble?

Cluster members chosen as representative members (RMs)


Forecast and analysis datasets

• data from TIGGE-PORTAL (everything in GRIB2);

• consider 180 forecast cases: 90 days (MAM09) of ECMWF-EPS and UKMO-

MOGREPS run at 00 and 12 UTC;

• use Z500 at fc+96h as clustering variable;

• for verifying analysis (at 00 and 12 UTC), consider Z500:

– “consensus analysis” (average of UKMO and ECMWF high-res analyses),

– independent analysis (e.g. from NCEP);

• generate the following global ensembles:

– EPS (50+1): 51 members

– MOGREPS (23+1): 24 members

– MINI-MIX (EPS24 + MOGREPS24): 48 members

– MEGA-MIX (EPS51 +MOGREPS24): 75 members


Strategy

• perform cluster analysis with 16 clusters and select RMs (like in operations);

• generate 16-member global ensembles (EPS_REDU, MOGREPS_REDU,

MINI_REDU, MEGA_REDU).

• How do “REDUs” ensembles rank with respect to EPS, MOGREPS, MINI-

MIX, MEGA-MIX?

• Where do the best (and the worst) elements of REDU ensembles come

from?

• How do they score depending on their “origin”?

• BEFORE DOWNSCALING: is there added value with respect to single-

model ensemble?


Future plans

finish by March 2010

Future future plans • Implement dynamical downscaling: nest COSMO model in the selected RMs and

generate “hybrid” COSMO-LEPS using boundaries from members of different

global ensembles.

• For a number of case, compare operational COSMO-LEPS and “hybrid”

COSMO-LEPS.


Thank you !


Operational set-up

Core products: 16 perturbed COSMO-model runs (ICs and 3-

hourly BCs from 16 EPS members) to generate, “via weights”, probabilistic output: start at 12UTC; t = 132h;

Additional products: 1 deterministic run (ICs and 3-hourly BCs from the

high-resolution deterministic ECMWF forecast) to “join” deterministic and probabilistic approaches: start at 12UTC; t = 132h;

1 hindcast (or proxy) run (ICs and 3-hourly BCs from ECMWF analyses) to “downscale” ECMWF information: start at 00UTC; t = 36h.


Score dependence on the domain size (1)

Verification of COSMO-LEPS against synop reports over the MAP D-PHASE area (~ 470 stations; MAPDOM) and the full domain (~ 1500 stations; fulldom):

different statistics of the verification samples; up to now, performance of the system over the 2 domains assessed only for 6

months (March-August 2007). difficult to draw general conclusions


Score dependence on the domain size (2)

RPSS

RPSS score… the higher the better… (and positive).

ROC area… the higher the better… (and above 0.6). Smoother transitions from month to month in “fulldom” scores.

Slightly better performance of COSMO-LEPS over the MAPDOM, but the signal varies from month to month.

Higher predictability with orographic forcing?

Need to check individual regions and/or to stratify for type of stations.

OUTL

ROC

Outliers percentage … the lower the better.


Overestimation of Td2m and soil moisture (1)

Verification period: MAM07 and MAM08.

Obs: synop reports (about 470 stations x day).

Region: 43-50N, 2-18E (MAP D-PHASE area).

Larger bias and larger rmse in MAM08 rather than in MAM07 for COSMO-LEPS deterministic run (in 2007, no multi-layer soil model).


Main results

• COSMO-LEPS system runs on a daily basis since November 2002 (6 “failures” in almost 6 years of activity) and it has become a “member-state time-critical application” at ECMWF ( ECMWF operators involved in the suite monitoring).

• COSMO-LEPS products used in EC Projects (e.g. PREVIEW), scientific experiments (e.g. COPS, MAP D-PHASE, EFAS) and met-ops rooms across COSMO community.

• Nevertheless, positive trends can be identified:• increase in ROC area scores and reduction in outliers percentages;• positive impact of increasing the population from 5 to 10 members (June

2004);• some deficiency in the skill of the system were identified after the system

upgrades occurred on Feb 2006 (from 10 to 16 members; from 32 to 40 ML + EPS upgrade!!!), but scores are encouraging throughout 2007 and, to a certain extent, 2008.

Time series scores cannot easily disentangle improvements related to COSMO-LEPS itself from those due to better boundaries by

ECMWF EPS.

2 more features:

• marked semi-diurnal cycle in COSMO-LEPS scores (better skill for “night-time” forecasts);

• better scores over the Alpine area rather than over the full domain (to be confirmed).


The COSMO-LEPS suite @ ECMWFNovember 2002 – May 2004

d-1d-1 dd d+5d+5d+1d+1 d+2d+2 d+4d+4d+3d+3

oldest EPSoldest EPS

1212

middle EPSmiddle EPS

oldest EPSoldest EPS

youngest EPSyoungest EPS


0000

1212



Z U V QZ U V Q

3 levels3 levels

500 700 850 hPa500 700 850 hPa





5 Representative 5 Representative MembersMembers

Driving the 5Driving the 5COSMO-model COSMO-model integrationsintegrations

COSMO-LEPS

Integration Domain

COSMO-LEPS

clustering area


The COSMO-LEPS suite @ ECMWFJune 2004 – January 2006

d-1d-1 dd d+5d+5d+1d+1 d+2d+2 d+4d+4d+3d+3

middle EPSmiddle EPS

youngest EPSyoungest EPS


0000

1212



Z U V QZ U V Q

3 levels3 levels

500 700 850 hPa500 700 850 hPa





COSMO-LEPS

Integration Domain

10 10 Representative Representative

MembersMembersdriving the 10driving the 10COSMO-model COSMO-model integrationsintegrations

employing either employing either Tiedtke or Kain-Tiedtke or Kain-Fristch scheme Fristch scheme

randomly randomly choosenchoosen

COSMO-LEPS

clustering area

• Suite running in real time at ECMWF managed by ARPA-SIM;

• Δx ~ 10 km• Fc length: 120h


COSMO-LEPS (developed at ARPA-SIM)

• What is it?It is a Limited-area Ensemble Prediction System (LEPS),

based on COSMO-model and implemented within COSMO (COnsortium for Small-scale MOdelling, which includes Germany, Greece, Italy, Poland, Romania, Switzerland).

• Why?It was developed to combine the advantages of global-

model ensembles with the high-resolution details gained by the LAMs, so as to identify the possible occurrence of severe and localised weather events (heavy rainfall, strong winds, temperature anomalies, snowfall, …)

generation of COSMO-LEPS to improve the Late-Short (48hr) to Early-Medium (132hr) range forecast of

severe weather events.

xi general cosmo meeting offenbach,7-10 september 2009

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