Transcript cosmo-leps - COSMO model

The COSMO-LEPS system:
getting close to the 5-year milestone
Andrea Montani, Chiara Marsigli and Tiziana Paccagnella
ARPA-SIM
Hydrometeorological service of Emilia-Romagna, Italy
IX General COSMO meeting
Athens,18-21 September 2007
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Outline
• Motivations
• Methodology of COSMO-LEPS
• Verification results:
– SYNOP on the GTS
• Future plans
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
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?
Because the horizontal resolution of global-model
ensemble systems is limited by computer time
constraints and does not allow a detailed description of
mesoscale and orographic-related processes.
The forecast of heavy precipitation events can still be
inaccurate (in terms of both locations and intensity)
after the short range.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
COSMO-LEPS project
 combine the advantages of global-model ensembles with
the high-resolution details gained by the LAMs, so as to
identify the possible occurrence of intense and
localised weather events (heavy rainfall, strong winds,
temperature anomalies, snowfall, …)
generation of COSMO-LEPS in order to improve
the Late-Short (48hr) to Early-Medium (132hr)
range forecast of the so-called “severe
weather events”.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
COSMO-LEPS methodology
Possible
evolution
scenarios
ensemble size
reduction
Cluster members chosen
as representative
members (RMs)
Initial conditions
Dim 1
LAM scenario
LAM scenario
LAM integrations driven by
RMs
LAM scenario
Initial conditions
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Dim 1
The COSMO-LEPS suite @ ECMWF
November 2002 – May 2004
d
d-1
d+1
d+2
d+3
d+4
d+5
4 variables
ZUVQ
3 levels
500 700 850 hPa
oldest EPS
oldest
EPS
12
middle EPS
00
Cluster Analysis and RM identification
youngest EPS
12
2
time
steps
European
area
Complete
Linkage
COSMOLEPS
Integratio
n Domain
COSMOLEPS
clustering
area
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
The COSMO-LEPS suite @ ECMWF
June 2004 – January 2006
d
d-1
d+1
d+2
middle EPS
00
d+3
d+4
d+5
4 variables
ZUVQ
3 levels
500 700 850 hPa
Cluster Analysis and RM identification
youngest EPS
12
COSMOLEPS
clustering
area
2
time
steps
European
area
Complete
Linkage
COSMOLEPS
Integratio
n Domain
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
•
•
•
Suite running in
real time at
ECMWF
managed by
ARPA-SIM;
Δx ~ 10 km
Fc length: 120h
The new COSMO-LEPS suite @ ECMWF
since February 2006
d
d-1
d+1
d+2
older EPS
00
d+3
d+4
d+5
4 variables
ZUVQ
3 levels
500 700 850 hPa
Cluster Analysis and RM identification
younger EPS
12
2
time
steps
European
area
Complete
Linkage
•
COSMOLEPS
clustering
area
COSMOLEPS
Integratio
n Domain
•
•
•
•
suite running as a ”timecritical application” managed
by ARPA-SIM;
Δx ~ 10 km; 40 ML;
COSM0-LM 3.20 since Nov06;
fc length: 132h;
Computer time (4.3 million BU
for 2007) provided by the
COSMO partners which are
ECMWF member states.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Present methodology
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Operational set-up
Core products:
 16 perturbed LM runs (ICs and 3-hourly BCs from
16 EPS members) to generate 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
assess the relative merits between deterministic and
probabilistic approach (start at 12UTC; t = 132h);
 1 “hindcast” run (ICs and 3-hourly BCs from ECMWF
analyses) to “downscale” ECMWF information (start at
00UTC; t = 36h).
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Dissemination
 probabilistic products
 deterministic products (individual COSMO-LEPS runs)
 derived probability products (EM, ES)
 meteograms over station points
products delivered at about 1UTC to the COSMO weather
services, to Hungary (case studies) and to the MAP DPHASE and COPS communities (field campaign).
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Objective verification of COSMO-LEPS
–
SYNOP on the GTS (COSMO-LEPS only);
Verification package includes the traditional probabilistic scores:
•Brier Skill Score (Wilks, 1995)
•ROC area (Mason and Graham, 1999)
•Cost-loss Curve (Richardson, 2000)
•Percentage of Outliers (Buizza, 1997)
•Ranked Probability Skill Scores (Wilks, 1995)
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Objective verification of COSMO-LEPS
–
SYNOP on the GTS (COSMO-LEPS only);
Main features:
variable: 12h cumulated precip (18-06, 06-18 UTC);
period:
from Dec 2002 to Aug 2007;
region:
43-50N, 2-18E (MAP D-PHASE area);
method: nearest grid point; no-weighted fcst;
obs:
synop reports (about 470 stations x day);
fcst ranges: 6-18h, 18-30h, …, 102-114h, 114-126h;
thresholds: 1, 5, 10, 15, 25, 50 mm/12h;
system:
COSMO-LEPS
both (57) monthly and (19) seasonal scores are computed.
work is in progress for verification over the full domain (1500 stations)
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Time series of Brier Skill Score
 BSS is written as 1-BS/BSref. Sample climate is the reference system. Useful forecast systems if BSS > 0.
 BS measures the mean squared difference between forecast and observation in probability space.
 Equivalent to MSE for deterministic forecast.
BSS
fc step: 30-42h
 improvement of
performance detectable
for all thresholds along
the years;
 still problems with high
thresholds, but good
trend in 2007.
Jun04: 5m  10m
Feb06: 10m16m; 32ML  40 ML
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Time series of ROC area
 Area under the curve in the HIT rate vs FAR diagram.
 Valuable forecast systems have ROC area values > 0.6.
ROC
fc step: 30-42h
fc step: 78-90h
 the positive impact of
increasing
the
ensemble size in 2004
is evident for all
thresholds
and
for
different fcst ranges.
 poor performance of
the system in Spring
and Summer 2006
(both particularly dry),
despite upgrades.
Jun04: 5m  10m
Jun04: 5m  10m
Feb06: 10m  16m; 32ML  40 ML
Feb06: 10m  16m; 32ML  40 ML
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Outliers: time series + seasonal scores
 How many times the analysis is out of the forecast interval spanned by the ensemble members.
 … the lower the better …
 Performance of the system assessed as time series and for 5 different Summers (JJA).
OUTL
 Evident seasonal cycle
(more
outliers
in
winter),
but
overall
reduction of outliers in
the years.
 Reduction of outliers
from one Summer to the
other, related to the
increase of ensemble
size (more evident for
the 5 to 10 increase).
 Need to take into
account the different
statistics
for
each
season (JJA 2003 less
rainy than the others).
Jun04: 5m  10m
Feb06: 10m  16m; 32ML  40 ML
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Semi-diurnal cycle in COSMO-LEPS scores
 BSS score … the higher the better …
 Performance of the system assessed for 5 different Summers (JJA).
BSS
 Evident 12-hour cycle in BSS
scores (the same holds for
RPSS, while less evident for
ROC area scores).
 Better performance of the
system
for
“night-time”
precipitation, that is for rainfall
predicted between 18Z and 6Z
(ranges 30-42h, 54-66h, …).
 The amplitude of the cycle is
somewhat reduced throughout
the years and with increasing
forecast range.
 The bad performance in
Summer 2006 is confirmed.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
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 the last 6 months
(March-August 2007).
 difficult to draw general conclusions
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Score dependence on the domain size (2)
 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.
 Outliers percentage … the lower the better.
RPSS
OUTL
ROC
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Main results
•
COSMO-LEPS system runs on a daily basis since November 2002 (6 “failures” in
almost 5 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) , field campaigns (e.g.
COPS, MAP D-PHASE) and met-ops rooms across COSMO community.
Time series scores cannot easily disentangle improvements related to
COSMO-LEPS itself from those due to better boundaries by ECMWF EPS.
•
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);
although some deficiency in the skill of the system were identified after the system
upgrades occurred on February 2006 (from 10 to 16 members; from 32 to 40 model
levels + EPS upgrade!!!), scores are encouraging throughout 2007.
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).
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Future plans
•
Verification vs synop: assess performance over the full domain and
consider other scores (Rank histograms, Reliability diagrams,…).
•
Implement “weighted” derived probability products:
– weighted ensemble mean;
– weighted ensemble standard deviation.
•
Introduce more model perturbations (see COSMO-SREPS approach).
•
Verification will be further developed → new variables verified.
•
Implement EFI index in the operational suite?
•
Implement “TIGGE-LAM compliant” COSMO-LEPS which can run on any
domain, on any boundary conditions (relocatable COSMO-LEPS).
•
Develop “hybrid” clustering (considering both ECMWF EPS and UKMO
MOGREPS) ---> work with GRIB2 format!
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Thank you !
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
MAM06
Average values (boxes 0.5 x 0.5)
tp > 1mm/24h
tp > 5mm/24h
COSMO-LEPS
16-MEMBER EPS
51-MEMBER EPS
As regards AVERAGE precipitation above
these two threshols, the 3 systems have
similar performance.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
ENSEMBLE SIZE REDUCTION
IMPACT EVALUATED ON CASE STUDIES (1)
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
2003082512 Friuli
(+72-+96)
A.Montani;
The COSMO-LEPS system: 5-year milestone
20 mm
100 mm
COSMO meeting, Athens, 18-21 September 2007
ENSEMBLE SIZE REDUCTION
IMPACT EVALUATED ON CASE STUDIES (2)
Observed precipitation between 15-11-2002 12UTC and 16-11-2002 12 UTC
Piedmont case
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
2002111212
Piedmont
A.Montani;
The COSMO-LEPS system: 5-year milestone
20 mm
150 mm
COSMO meeting, Athens, 18-21 September 2007
COSMO-LEPS
Real time products
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Operational COSMO-LEPS ~ Operational EPS
S.E. 153
5 RMs
“Friuli case”
The youngest
EPS
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Operational COSMO-LEPS ~ Operational EPS : Friuli case
probability maps – fc. range +96
>20mm/24h
>50mm/24h
COSMO
LEPS
EPS
51
members
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
EVALUATION OF S.E. SIZE (either 51, or 102, or 153) &
ENSEMBLE SIZE REDUCTION (either 5 or 10 RMs)
BSS
outliers
 Regarding the impact of the ensemble size, the
 Regarding the 5-RM ensembles results would seem to
difference between each 5-member ensemble and the
suggest that the use of just two EPS in the supercorrespondent 10-member ensemble is
ensemble can be a good compromise, permitting to
remarkable.The impact of doubling the ensemble size
decrease the percentage of outliers significantly with
is almost the same for every configuration and is
respect of using just 1 EPS but leading only to a small
larger than impact of changing the number of EPSs
decrease of the skill.
on which the Cluster Analysis is performed (2 or 3).
old suite new suite
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
TEST OF NEW CLUSTERING VARIABLES AND/OR DIFFERENT
CLUSTERING INTERVALS
 Consider a fixed configuration in terms of ensemble size (10 RMs selected out of 2 EPS sets, 2eps-10rm) and
the properties of the “reduced” (10-member) global ensemble in 4 different cases:
OPE:
the 10 members are selected like in the operational set-up (clustering variables: z,u,v,q;
clustering levels: 500, 700, 850 hPa; clustering times: fc+96h, fc+120h);
D2:
like OPE, but clustering times: fc+24h, fc+48h;
D3:
like OPE, but clustering times: fc+48h, fc+72h;
D4:
like OPE, but clustering times: fc+72h, fc+96h.
outliers
BSS
Brier Skill Score: OPE has slightly better scores at all verification ranges (less evident for ROC area .. not shown);
Outliers percentage: results heavily depends on the verification range.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
COSMO-LEPS derived probability products
The generation of the Ensemble Mean (EM) and Ensemble Standard
deviation (ES) was implemented and tested for COSMO-LEPS runs in
terms of:
Z700 - T850 – MSLP - T2M - UV10M - TP
from fc+0h to fc+132h every 3 hours
Dissemination will start at the end of the month.
EM and ES are calculated without considering the weights relative to
each integration.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Why Limited Area Ensemble Prediction?
• Global Ensemble Prediction Systems
– have become extremely important tools to tackle the
problem of predictions beyond day 2
– are usually run at a coarser resolution with respect to
deterministic global predictions → skill in forecasting
intense and localised events is currently still limited.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Why Limited Area Ensemble Prediction?
(2)
As regards high resolution deterministic forecast in the short range,
where limited-area models play the major role, a “satisfactory” QPF
is still one of the major challenges. The same can be said for other
local parameters.
This is due, among other reasons, to the inherently low degree of
predictability typical of severe and localised events.
Probabilistic/Ensemble approach is so required also for the short
range at higher resolution
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
From Global EPS to LAM EPS
• In the Limited-area ensemble systems, tailored for the short
range, perturbations must be already “active” during the first
hours of integration
• The characteristic of the LAM ensemble are strongly dependent
by the lateral boundaries forcing.
• Due to the “regional” application of these Limited Area
Ensembles, methodologies can be different in different
geographycal regions.
A pratical consideration:
Global EPS ~ Big Centres
Limited Area EPS ~ (also) Relatively Small Centres
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
OBJECTIVE VERIFICATION OF COSMO-LEPS
In the last period the verification package is being
developed keeping into account two measure of
precipitation:
the cumulative volume of water deployed over a
specific region
the rainfall peaks which occur within this region
COSMO observations
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
OBS MASK
CLEPS
EPS
Verification grid
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Archiving of C0SMO-LEPS
From July 2005, products are archived on MARS at ECMWF
Deterministic run (fc+0h to fc+132h every 3h).
Ensemble Prediction System:
16 perturbed forecasts (fc+0h to fc+132h every 3h):
PLEV (500, 700, 850 hPa): Z, RH, T.
SURF: albedo, LCC, MCC, TCC, SW radiation flux, CAPE, hzerocl, snowlmt,
mslp, T_2m, Td_2m, TMAX_2m, TMIN_2m, U_10m, V_10m, UVMAX_10m,
large-scale rain, convective rain, large-scale snow, TP.
Forecast probability (various intervals and thresholds):
SURF: CAPE, hzerocl, TMAX_2m, TMIN_2m, UVMAX_10m, TP, snowfall,
showalter index.
Clustering information (population, clustering variable used, …).
Derived products (fc+0h to fc+132h every 3h):
ens-mean and ens-spread: Z700, T850, MSLP, T2M, UV10M, TP.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
3 sis
Average values boxes 0.5x0.5 deg
tp > 1mm/24h
tp > 5mm/24h
COSMO-LEPS
16-MEMBER EPS
51-MEMBER
EPS
A.Montani;
The COSMO-LEPS
system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
NOCC=2671
tp > 1mm/24h
ave 0.5
NOCC=1195
tp > 5mm/24h
NOCC=610
tp > 10mm/24h
COSMO-LEPS
A.Montani; The COSMO-LEPS system: 5-year milestone
16-MEMBER
EPS 18-21 September 2007
COSMO
meeting, Athens,
3 sis
Maximum values boxes 0.5x0.5 deg
tp > 1mm/24h
tp > 5mm/24h
COSMO-LEPS
16-MEMBER EPS
51-MEMBER EPS
tp > 10mm/24h
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Average values boxes 0.5x0.5 deg
NOCC=227
tp > 20mm/24h
COSMO-LEPS
16-MEMBER EPS
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Precipitation: average
tp > 10mm/24h
COSMO-LEPS
5-MEMBER EPS
51-MEMBER EPS
ROC area
on 1.5 x 1.5 boxes
tp > 20mm/24h
As regards AVERAGE precipitation above
these two threshols, EPS wins.
Worsening due to the ensemble reduction
2003
Positive impact of LMSON
downscaling
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
maxima
ROC area
COSMO-LEPS
on 1.5 x 1.5 boxes
tp > 20mm/24h
5-MEMBER EPS
51-MEMBER EPS
COSMO-LEPS is more skilful than
EPS in forecasting correctly high
precipitation values over a rather
large area.
tp > 50mm/24h
Number of occurrences: 600 (20 mm
threshold) and 150 (50 mm).
SON 2003
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Time series of ROC area for COSMO-LEPS
(2)
 Area under the curve in the FAR vs HIT diagram.
 Valuable forecast systems have ROC area values > 0.6
ROC
fc step: 78-90h
 the positive impact of
increasing the ensemble
size in 2004 is evident
for all thresholds and for
different fcst ranges.
 poor performance of the
system in Spring and
Summer 2006, despite
system upgrades.
Jun04: 5m  10m
Feb06: 10m  16m; 32ML  40 ML
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
MAM06
Average values (boxes 0.5 x 0.5 deg)
COSMO-LEPS
16-MEMBER EPS
51-MEMBER EPS
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Time series of TEST OF NEW CLUSTERING VARIABLES AND/OR
DIFFERENT CLUSTERING INTERVALS
 Consider a fixed configuration in terms of ensemble size (10 RMs selected out of 2 EPS sets, 2eps-10rm) and
the properties of the “reduced” (10-member) global ensemble in 4 different cases:
OPE:
the 10 members are selected like in the operational set-up (clustering variables: z,u,v,q;
clustering levels: 500, 700, 850 hPa; clustering times: fc+96h, fc+120h);
D2:
like OPE, but clustering times: fc+24h, fc+48h;
D3:
like OPE, but clustering times: fc+48h, fc+72h;
D4:
like OPE, but clustering times: fc+72h, fc+96h.
outliers
BSS
Brier Skill Score: OPE has slightly better scores at all verification ranges (less evident for ROC area .. not shown);
Outliers percentage: results heavily depends on the verification range.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Main results
•
COSMO-LEPS system runs on a daily basis since November 2002 and it has
become a “member-state time-critical application” at ECMWF ( partial
involvement of ECMWF operators in the suite management).
•
Time series scores identify positive trends in the performance of the system:
•
•
•
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 identified after the system upgrades occurred
on February 2006 (from 10 to 16 members; from 32 to 40 model levels + EPS
upgrade!!!)  need of further investigation.
•
High-resolution verification shows better scores of COSMO-LEPS with respect to
EPS in forecasting precipitation maxima within boxes.
•
No clear impact of the weighting procedure as regards precipitation, BUT
COSMO-LEPS ensemble mean for 2m temperature has better skill (lower standard
deviation to observations) with weighting the ensemble members according to
cluster populations compared to the mean with unweighted members.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Downscaling
Total
Downscaling
LAM
Nesting
Global
Ensemble
GCM members
LAM members
Ensemble
Size
Reduction
Global
Ensemble
(Brute-Force Approach)
COSMO
LAM
Nesting
LEPS
Approach
LAM members
GCM members
Representative
members
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
COSMO-LEPS forecast for 72h precipitation
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
Probability precipitation > 250mm/72h
C. Frei, MeteoSwiss
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
Standard deviation: 2m temperature 12UTC
3.5
3.5
DJF 2004/2005
0C
3.0
3.0
2.5
2.5
aLMo
2.0
JJA 2005
0C
2.0
aLMo
CLEPS mean uw
CLEPS mean uw
CLEPS mean w
CLEPS mean w
1.5
1.5
0
24
48
72
96
Forecast range (h)
STD2 = RMS2 – BIAS2
120
0
24
48
72
96
120
Forecast range (h)
uw: unweighted / w: weighted according to cluster population
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
COSMO-LEPS weighting procedure
maximum values (boxes 0.5x0.5 deg)
tp > 1mm/24h
COSMO-LEPS NW
COSMO-LEPS W
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Outliers: time series + seasonal scores
 How many times the analysis is out of the forecast interval spanned by the ensemble members.
 … the lower the better …
 Performance of the system assessed for 4 different Autumns.
OUTL
 Continuous reduction of
outliers from one year
to the other, also
related to the increase
of ensemble size (more
evident for the 5 to 10
increase, rather than
from 10 to 16).
 Need to take into
account the different
statistics
for
each
season (SON 2006 less
rainy than the others).
Jun04: 5m  10m
Feb06: 10m  16m; 32ML  40 ML
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
COSMO-LEPS weighting procedure
average values (0.5x0.5 boxes)
tp > 1mm/24h
maximum values (0.5x0.5 boxes)
COSMO-LEPS NW
COSMO-LEPS W
tp > 1mm/24h
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Synop-Verification: COSMO-LEPS & aLMo
aLMo: - deterministic 7 km model (45 levels) of MeteoSwiss for 72h forecasts
- same code (LM) as COSMO-LEPS
aLMo domain
Common
verification
domain,
about 1000
synop stations
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
Standard deviation: 2m temperature 00UTC
3.5
3.5
DJF 2004/2005
0C
3.0
3.0
2.5
2.5
aLMo
2.0
JJA 2005
0C
aLMo
CLEPS mean uw
CLEPS mean w
2.0
CLEPS mean uw
w
CLEPS mean uw
1.5
1.5
0
24
48
72
96
Forecast range (h)
STD2 = RMS2 – BIAS2
120
0
24
48
72
96
120
Forecast range (h)
uw: unweighted / w: weighted according to cluster population
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
Case study: flood event in Switzerland in August 2005
Courtesy of Andrè Walser (Meteoswiss)
Photos:Tages-Anzeiger
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Synoptic overview: 22 August 2005
Temperature 850 hPa and geopotential 500 hPa:
18º
10º
2º
by AW (Meteoswiss)
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Total precipitation over 3 days (20/8 – 23/8)
(06 - 06 UTC)
C. Frei, MeteoSwiss
About 400 stations, precipitation sum locally over 300 mm!
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
COSMO-LEPS forecast for 72h precipitation
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
COSMO-LEPS vs ECMWF EPS
probability of 72h cumulated precipitation
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
Probability precipitation > 100mm/72h
C. Frei, MeteoSwiss
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
Probability precipitation > 100mm/72h
C. Frei, MeteoSwiss
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
by AW (Meteoswiss)
Objective verification of COSMO-LEPS
–
high-resolution network (COSMO-LEPS vs ECMWF EPS)
Main features:
variable: 24h cumulated precip (06-06 UTC);
period:
MAM 2006;
region:
Germany, Switzerland, Italy;
method:
BOXES (0.5 x 0.5);
obs:
COSMO network (2500 stations x day);
fcst ranges: 18-42h, 42-66h, 66-90h, 90-114h;
thresholds: 1, 5, 10, 20, 50 mm/24h;
systems:
- COSMO-LEPS (16m, 10 km, 40 ML)
- reduced EPS (16m, 50 km, 60 ML)
- full EPS
(51m, 50 km, 60 ML)
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
Verification of the distributions
The verification has been made in terms of:
• Average value
• Maximum value
• 50th percentile (Median)
in a box
• 90th percentile
Station observation
Grid point forecast
two measures of precipitation:
 the cumulative volume of
water deployed over a
specific region;
 the rainfall peaks occurring
within the same region.
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
MAM06
Maximum values (boxes 0.5 x 0.5)
NOCC=3681
tp > 1mm/24h
NOCC=2492
tp > 5mm/24h
COSMO-LEPS
16-MEMBER EPS
51-MEMBER EPS
NOCC=1592
tp > 10mm/24h
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007
MAM06
Maximum values (boxes 0.5 x 0.5)
COSMO-LEPS is more skilful than
EPS in forecasting correctly high
precipitation values over 0.5 x 0.5
boxes.
COSMO-LEPS
16-MEMBER EPS
51-MEMBER EPS
A.Montani; The COSMO-LEPS system: 5-year milestone
COSMO meeting, Athens, 18-21 September 2007