Limited-Area Ensemble Prediction: the ARPA-SMR LEPS system Stefano Tibaldi, Tiziana Paccagnella,
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Transcript of Limited-Area Ensemble Prediction: the ARPA-SMR LEPS system Stefano Tibaldi, Tiziana Paccagnella,
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
Limited-Area Ensemble Prediction: the ARPA-SMR LEPS system
Stefano Tibaldi, Tiziana Paccagnella,
Chiara Marsigli, Fabrizio Nerozzi, Andrea Montani ARPA-SMR
With contributions from F.Molteni, R.Buizza and H.Hersbach, all at ECMWF, at some time
Limited-Area Ensemble Prediction: the ARPA-SMR LEPS system
Stefano Tibaldi, Tiziana Paccagnella,
Chiara Marsigli, Fabrizio Nerozzi, Andrea Montani ARPA-SMR
With contributions from F.Molteni, R.Buizza and H.Hersbach, all at ECMWF, at some time
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
• The need for the regionalisation of scenarios
• The LEPS approach– Methodology– Some case studies– Statistical evaluation
• COSMO-LEPS
• Concluding remarks
OUTLINE OUTLINE
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
THE NEED FOR REGIONALISATION OF SCENARIOS (1)
THE NEED FOR REGIONALISATION OF SCENARIOS (1)
Despite the recent increase of computer power resources, which have allowed the development of more and more sophisticated NWP models, the accurate forecast of extreme weather conditions, especially when related to intense and localised precipitation structures, is still difficult.
This limitation is due, among other reasons, to the inherent low degree of deterministic predictability associated to this kind of phenomena.
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
THE NEED FOR REGIONALISATION OF SCENARIOS (2)
THE NEED FOR REGIONALISATION OF SCENARIOS (2)
Global-model ensemble systems have been shown to be important tools to tackle the predictability problem beyond day 3.
Operational ensemble systems are usually run at a coarser resolution with respect to single deterministic model integrations for obvious economy reasons.
The EPS skill in producing quantitative forecasts of intense and localised events in the short- and early-medium-range is still limited, although growing.
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
THE LEPS APPROACHTHE LEPS APPROACH
The main purpose of the LEPS project is to produce a system capable of providing the forecaster some probabilistic guidance to identify the possible occurrence of severe weather conditions in the time range:
“late-short-range (>48h) up to early-medium-range (120h)”.
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
THE LEPS APPROACHTHE LEPS APPROACH
LEPS is designed to combine in a single systemthe (supposed) ability of a global ensemble prediction system to generate an exhaustive set of large-scale evolution scenarios (through an adequate sampling of the phase-space in the neighbourhood of the best available initial conditions)
Withthe (supposed) capability of a LAM of detailing atmospheric phenomena on the local scales, particularly the precipitation field, in regions with complex orography
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The obvious solution: one LAM integration
for each global EPS member
All the information from the global EPS is retained
BUT
it is hardly feasible on an operational basis (at least
at ARPA-SMR)
The B.F. (Brute Force) APPROACH
The B.F. (Brute Force) APPROACH
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
For each LAM run:
Computer time:
+120 hours of LAM integration
306 x 258 x 32 grid points
13 hours cpu on vpp5000
Data volume (IC and BCs):
0.9 GB for each member
B.F.: REQUIRED RESOURCES(evaluated on COSMO-LEPS
configuration)
B.F.: REQUIRED RESOURCES(evaluated on COSMO-LEPS
configuration)
51 runs
663 hours cpu!
46 GB!
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
The LAM is nested in only a limited number of
members selected from the global EPS, the
Representative Members
Some of the information from global EPS is lost
BUT
the operation becomes feasible on an operational basis
THE LEPS APPROACHTHE LEPS APPROACH
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Most Representative Member
one per cluster choice is based on selected 3D fields: has to be: the closest to the mean of its own cluster AND the most distant to the other clusters’ means 5 runs instead of 51, 102 or 153!!
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
Dim 2
Initial conditions Dim 1
LEPS – Limited area Ensemble Prediction SystemLEPS – Limited area Ensemble Prediction System
Dim 2
Possible evolution scenarios
Dim 1 Initial conditions
EPS and ensemble size reduction
Cluster members chosen as representative members (RMs)
LAM integrations driven byRMs
LAM scenario
LAM scenario
LAM scenario
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
LEPS – Limited area Ensemble Prediction SystemLEPS – Limited area Ensemble Prediction System
Dim 2
Initial conditions
Dim 1
LAM scenario
LAM scenario
LAM scenario
PROBABILITY MAPS: WEIGHTING??????PROBABILITY MAPS: WEIGHTING??????
precipitation scenarios
precipitation scenarios
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
The basic idea was to leave the task of exploring the phase space to the global EPS, while the LAM has to zoom in the forecast,
producing adequately intense local phenomena (e.g. precipitation maxima),
but….
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
Precip outliers 91 ECMWF EPS DJF 1999/2000
TP ACC 24 H BELOW MIN
ABOVE MAX
OUTLIERS %
D+3 8.3 5.6 13.9 D+5 4.6 2.8 7.3
EPS
both 4.1 1.7 5.8
D+3 13.6 24.9 38.6 D+5 9.7 17.2 26.9
5 RM
(c.linkage) both 9.4 16.8 26.1
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
QUESTIONS:
Are we adequately sampling the space of possibilities (i. e. the phasespace around the initial conditions)?
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The same 700hPa isoline plotted for the 51 Members at + 72
The same 700hPa isoline plotted for the 51 Members at + 120
Spread: EPS started at 14 May 1999, 00 UTC
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
Z 500 DJF 1999-2000AREA 28°N - 60°N; 18°W - 45°E
0.0
0.5
1.0
1.5
2.0
0 2 4 6 8 10 12 14
FC DAY
MSS
MSE EM
MSE CTRL
Spread vs errorMean square error/mean square spread
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
How can we improve our exploration
of the phase space, increasing the
available number of EPS forecasts?
By resurrecting the old concept of
time-lagged ensemble forecast!
The Super-Ensemble!
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
Precip outliers 91 ECMWF EPS DJF 1999/2000
TP ACC 24 H BELOW MIN
ABOVE MAX
OUTLIERS %
D+3 8.3 5.6 13.9 D+5 4.6 2.8 7.3
EPS
both 4.1 1.7 5.8
D+3 13.6 24.9 38.6 D+5 9.7 17.2 26.9
5 RM
(c.linkage) both 9.4 16.8 26.1
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
LEPS super-ensembleLEPS super-ensemble
start of integrations
102members Day n EPS
Day n
Day n-2 EPS
Day n-2
clustering time
Verification period
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
102 members (50 + 1)*2
5 representative members (RMs)
Summary of the LEPS Summary of the LEPS methodology methodology
5 LAMBO integrations nested on 5 RMs:
LEPS - Limited-area (High Resolution) Ensemble Prediction System
5 LAMBO integrations nested on 5 RMs:
LEPS - Limited-area (High Resolution) Ensemble Prediction System
5 clusters
Hierarchical Cluster Analysismethod: Complete Linkage
area: Southern Europefields: 4 variables at 4 levels (3D cluster)
number of clusters: fixed to 5
Hierarchical Cluster Analysismethod: Complete Linkage
area: Southern Europefields: 4 variables at 4 levels (3D cluster)
number of clusters: fixed to 5
Representative Member Selection one per cluster
base on the nearest (3D fields) to the mean of its own cluster AND the most distant to the other clusters’
means
Representative Member Selection one per cluster
base on the nearest (3D fields) to the mean of its own cluster AND the most distant to the other clusters’
means
Super ensemble:2 global ensembles starting 5/3 days before the
verification time
Super ensemble:2 global ensembles starting 5/3 days before the
verification time
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
LEPS:
SOME CASE STUDIES
LEPS:
SOME CASE STUDIES
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Soverato: 8, 9, 10 - Sep - 2000
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
Soverato flood
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Soverato (Calabria) flood
ECMWF proxy of 24h cumulated precipitation 10/09/2000 at 00Z
91
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Between 9 and 10 September, rainfall peaks above 300 mm in 24 Between 9 and 10 September, rainfall peaks above 300 mm in 24 hours were recorded close to the village of Soverato this causing hours were recorded close to the village of Soverato this causing landslides, great disruption and losses oflandslides, great disruption and losses oflife.life.
8 9 10
8 9 10
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
ECMWF probability maps for 24h cumulated precipitation exceeding P
threshold at +60h
P > 20 mm/ 24 h
P > 50 mm/ 24 h
P > 100 mm/ 24 h
Ensemble T255
Soverato (Calabria) flood
30
100
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
P > 20 mm/ 24 h
P > 50 mm/ 24 h
P > 100 mm/ 24 h
LEPS probability maps for 24h cumulated precipitation exceeding P threshold at
+60h
LEPS – 5 LAMBO runs driven by the 5 RMs selected from 153 members of the Super-Ensemble TL255
Soverato (Calabria) flood
47
75 5
8
42
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Probability maps for 24h cumulated precipitation exceeding threshold at +60h
Brute-force approach
51 LAMBO runs on ensemble EPS TL255L40
(51 members)P > 50 mm / 24 h
33
23
Soverato (Calabria) flood: BF vs LEPS
2554
LEPS:
5 weighted LAMBO runs on ensemble EPS TL255L40
P > 50 mm / 24 h
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
MAP IOP2b: 19, 20 - Sep - 1999
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
24 hours observed precipitation from 06 to 06 UTC
MAP IOP 2B, 20-21 September 1999
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
ECMWF probability maps for 24h cumulated precipitation exceeding threshold at +66
hours
ECMWF EPS forecasts 51 members
P > 20mm/24h
MAP IOP 2B
P > 50mm/24h
98%
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
LEPS probability maps for 24h cumulated precipitation exceeding threshold at +66
hours
LEPS:
5 LAMBO runs at 20 km on Super-Ensemble TEPS TL159
P > 20mm/24h
MAP IOP 2B
P > 50mm/24h
WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002
Probability maps for 24h cumulated precipitation exceeding threshold at +66
hours
P > 50mm/24h
P > 50mm/24h
Brute-force approach
51 LAMBO runs on TEPS TL159 (51 members)
MAP IOP 2b BF vs LEPS LEPS:
5 weighted LAMBO runs at 20 km on
ensemble EPS TL159