a.montani; the cosmo-leps system. cosmo-leps: present status and developments andrea montani, d....

A.Montani; The COSMO-LEPS system.

COSMO-LEPS: present status and

developments

Andrea Montani,

D. Cesari, C. Marsigli, T. Paccagnella

ARPA-SIMC

HydroMeteoClimate Regional Service of Emilia-Romagna, Bologna,

Italy

XIII COSMO General meetingRome, 5-8 September 2011


Outline

• Recent upgrades of COSMO-LEPS: use of soil-moisture analysis fields from COSMO-EU;

• Performance of the system: time-series verification of COSMO-LEPS using SYNOP;

• Implementation of 00UTC COSMO-LEPS: present situation and future developments;

• Implementation of SOCHMEL (“Sochi ensemble”).• Work for LAMEPS_BC project.• Modifications to the clustering/selection technique.• Summary and plans.


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 scheme and turbulence scheme and in physical in physical

parameterisationsparameterisations

COSMO-LEPS

clustering area

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

• Δx ~ 7 km; 40 ML; fc+132h;• COSM0 v4.12 since July

2010;• computer time (20 million

BUs for 2011) provided by the COSMO partners which are ECMWF member states.

COSMO-LEPS

Integration Domain


Outline

• Recent upgrades of COSMO-LEPS: use of soil-moisture analysis fields from COSMO-EU;


Upgrades during the “COSMO year”

• 9 November 2010: the deterministic run (LMDET) takes the ICs from the soil fields provided by the proxy-run mixed with some ECMWF fields (soil-proxy); COSMO-LEPS output (up to fc+60h; last 3 months) is saved on ML to enable further downscaling;

• 11 April 2011: COSMO-LEPS members use, as ICs, the soil fields provided by COSMO-EU (soil-merge); perturbation values are tuned and new perturbations are introduced; upgrade of INT2LM to version 1.18 (with grib_api).

• 5 July 2011: ECMWF EPS members are saved on ML over a large domain to enable reruns (last 3 months).

No upgrades of COSMO since July 2010 (using model version 4.12)


Oper system (interp)

x = 7 kmfcst range = 132hinitial conditions: interpolated

from EPS members;

perturbations: type of convection scheme; tur_len; pat_len; crsmin; rat_sea; rlam_heat.

COSMO-LEPS with soil-moisture fields from COSMO-EU

Test system (merge)

x = 7 kmfcst range = 48hinitial conditions: interpolated

from EPS members merged with surface and soil-layer fields from COSMO-EU (T_SO, W_SO, W_ICE, W_I, FRESHSNW, RHO_SNOW, W_SNOW, T_SNOW).

perturbations: type of convection scheme; tur_len; pat_len; crsmin; rat_sea; rlam_heat; mu_rain; cloud_num.“Oper” and “Test” were run in parallel from 1/12/2010 to

15/3/2011 (> 100 cases).


BIAS of T2M Ensemble Mean

bias computed over 3 different domains for the period 1/12/2010 15/3/2011 (> 100 cases).

—— oper (interp) —— test (merge)

T2m forecasts are corrected with height

fulldom (~1400 synop)

mapdom (~410 synop)

mapdom < 100m (~50 synop)

Bias closer to zero for “test” ensemble, which uses the soil moisture fields from COSMO-EU.

Smaller amplitude in bias oscillations for “test”. fulldom and mapdom: the improvement is

systematic for all forecast ranges; the cold bias of “oper” is reduced.

mapdom < 100m: large reduction of bias for day-time verification; increase of the bias for night-time verification.


MAE of TD2M Ensemble Mean

mae computed over 3 different domains for the period 1/12/2010 15/3/2011 (> 100 cases).

Lower mae for “test” ensemble, which uses the soil moisture fields from COSMO-EU.

fulldom and mapdom: the mae reduction is small, but systematic and lasts for about 2 forecast days.

mapdom < 100m: the mae reduction is more evident.

—— oper (interp) —— test (merge)

fulldom (~1400 synop)

mapdom (~410 synop)

mapdom < 100m (~50 synop)


Summary of results for soil-merge experiments

T2M and TD2M:• reduction of bias and mean-absolute error if the COSMO-LEPS members take the initial conditions from the soil moisture fields provided by COSMO-EU;• the improvement is confirmed over larger and smaller domains;• the reduction of errors lasts for more than 2 forecast days;

TOT_PREC: • the impact is neutral (not shown).

Soil-merge was successfully implemented in the operational COSMO-LEPS suite on 11 April 2011 (… and no problems since then!)

the transfer of SMA files from DWD to ECMWF is solid and timely.++


Outline

• Performance of the system: time-series verification of COSMO-LEPS using SYNOP;


– SYNOP on the GTS

Time-series verification of COSMO-LEPS

Main features:

variable: 12h cumulated precip (18-06, 06-18

UTC);

period : from Dec 2002 to Jul 2011;

region: 43-50N, 2-18E (MAP D-PHASEPHASE

area);

method: nearest grid point; no-weighted fcst;

obs: synop reports (about 470

stations/day);

fcst ranges: 6-18h, 18-30h, …, 102-114h, 114-126h;

thresholds: 1, 5, 10, 15, 25, 50 mm/12h;

system: COSMO-LEPS;

scores: ROC area, BSS, RPSS, Outliers, …

both monthly and seasonal scores were computed


Time series of ROC areaArea under the curve in the HIT rate vs FAR diagram; the higher, the better …Valuable forecast systems have ROC area values > 0.6.

Improvement of skill detectable during 2010 and 2011 for all but the highest threshold.

In 2011, few events with heavy precipitation: possible lack of significance of the results for the 15mm threshold.

Limited loss of predictability with increasing forecast range.

fc 30-42h: ROC area is low for the 15mm threshold: WHY?

fc 78-90h: in the last months, ROC area values have shown little dependence on the threshold.


Seasonal scores of ROC area: the last 4 springs

Fixed event (“12h precip > 5mm”): consider the performance of the system for increasing forecast ranges.

Fixed forecast range (fc 30-42h): consider the performance of the system for increasing thresholds.

Valuable forecast systems have ROC area values > 0.6.Need to take into

account the different statistics for each season (last MAM was the driest).

Best performance for the spring 2011 (with a good advantage), for all forecast ranges and thresholds.

Similar results for longer forecast ranges or higher thresholds (not shown).


Outliers: time series + seasonal scoresHow 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 the last 4 winters.

Evident seasonal cycle (more outliers in winter).

Overall reduction of outliers in the years up to 2007; then, again in 2009 and 2010, but not in 2011.

Need to take into account the different statistics for each season.

In the short range, best results for last winter.

For longer ranges, the performance of the system is “stable”.

Outliers before 10% from day 2 onwards.


Ranked Probability Skill Score: time series + seasonal scores

A sort of BSS “cumulated” over all thresholds. RPSS is written as 1-RPS/RPSref. Sample climate is the reference system. RPS is the extension of the Brier Score to the multi-event situation.

Useful forecast systems for RPSS > 0. Performance of the system assessed as time series and for the last 4 springs (MAM).

the increase of the COSMO-LEPS skill is detectable for 3 out of 4 forecast ranges along the years;

RPSS positive for all forecast ranges since May 2008; encouraging trend in the last year.Good results for MAM 2011 (12h-cycle of the score).


Outline

• Implementation of 00UTC COSMO-LEPS; present situation and future developments;


COSMO-LEPS @ 00UTC

Background:

Due to the increasing use and interest in COSMO-LEPS products, a new ECMWF time-critical application was prepared and sent to ECMWF as for the implementation of COSMO-LEPS also at 00UTC (cleps00).

Main features:• same configuration as present cleps12 (modify cluster analysis??);• post-processing will be done using Fieldextra;• cleps00 will run in the late morning, interacting with ECMWF system sessions

product delivery might be occasionally delayed a few hours.

Present situation:• depending on ECMWF comments/suggestions, cleps00 could be implemented by

the end of 2011 (test products should be available earlier!).


• Implementation of SOCHMEL (“Sochi ensemble”);

Outline

Sochi (RU)

Rome (I)


SOCHMEL (SOCHi-targeted Mesoscale EnsembLe system)

1) Next Olympics and Paralympics Winter Games will take place in Sochi, Russia (7-23 February and 7-16 March 2014).

2) For this event, WMO launched a WWRP RDP/FDP initiative, named FROST-2014 (Forecasting and Research: the Olympic Sochi Testbed)????????

3) COSMO will perform a number of activities related to Sochi-2014 WWRP RDP/FDP:

a) deterministic forecasting,

b) probabilistic forecasting:

b1) FDP initiatives (“clone” of COSMO-LEPS over the Sochi area),

b2) RDP initiatives (development of a COSMO LAM-EPS system for the Sochi area).

c) post-processing and product generation,

d) verification.


FDP (Forecast Demonstration Project) initiatives

SOCHMEL7: limited-area ensemble system based on COSMO(“relocation” of COSMO-LEPS)

Horizontal resoluzion: 7 km.Vertical resolution: 40 model levels.Forecast range: 72 hours.Starting time: 00UTC, 12UTC.Ensemble size: 10 members.Boundary conditions: from selected ECMWF EPS members.Initial conditions: interpolated from ECMWF EPS members.

Timetable

Pre-trial: 2011/12 winter

Trial: 2012/13 winter

Olympics: 2014 winter.


SOCHMEL suite @ ECMWF: present status

d+3d+3dd d+2d+2d+1d+1

ECMWF EPSECMWF EPS

clustering clustering intervalinterval


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


Black-Sea Black-Sea areaarea

Complete Complete LinkageLinkage

1010 Representative Representative Members driving the Members driving the 1010

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 scheme and turbulence scheme and in physical in physical

parameterisationsparameterisations

SOCHMEL

clustering area

• Δx ~ 7 km; 40 ML; fc+72h;• initial time: 00UTC, 12UTC;• for the moment, computer time

(10 million BU for 2012) provided by an ECMWF Special Project;

• suite managed by ARPA-SIMC; • contributions from ECMWF

member states could be needed in the future.

SOCHMEL Integration

Domain

As for the future, apply for an ECMWF time-critical application


Outline

• Work for LAMEPS_BC project;


LAMEPS_BC project: background

Aim: generation of EPS boundary conditions (at 6 and 18 UTC) for use of LAMEPS community

Preliminary issue: to make progress in terms of increasing the efficiency of archiving and retrieving EPS data.

The solution: to archive the data on the native reduced Gaussian grid of the ECMWF IFS, but only in a region of interest over the Northern Atlantic and Europe (a bitmap mask is applied so that only data in the masked region are coded in GRIB).

The next step: to check if the regionally archived EPS data can be used by the LAMEPS groups.


LAMEPS_BC project: present situation

1) For one case study, ECMWF fields were archived both globally (as generated by the operational EPS) and regionally (data are on a reduced gaussian grid N320 for all fields).

2) LAMEPS groups are running their LAMEPS systems taking the boundary conditions from both experiments and comparing the forecasts.

3) As for COSMO-LEPS, cleps_g takes the globally-archived boundaries; cleps_r takes the regionally-archived boundaries:

a) upper-level fields: no differences are found for between cleps_g and cleps_r;

b) surface fields (2-metre temperature and precipitation): a few differences are found between cleps_g and cleps_r; differences are confined to very few grid points, but are not negligible. Further investigation is in progress.For problems relative to ECMWF data, contact M. Leutbecher.


Outline

• Modifications to the clustering/selection technique.


Test modifications of clustering methodologies

• always select control runs by ECMWF EPS:• a new 16-member ensemble (ctrl-LEPS) was created by taking the first 14

members from COSMO-LEPS and adding 2 more members nested on 00UTC and 12UTC the EPS control members;

• ctrl-LEPS was compared to COSMO-LEPS for 3 months;• as for precipitation forecasts, the two systems have identical performance;• further investigation is needed to assess spread/skill relationship of both

systems.

• consider shorter forecast ranges for clustering intervals (e.g.: 48-72h, 72-96h);

• select the Representative Members from only one EPS:• could be strategic in view of having COSMO-LEPS at both 00 and 12UTC.


Outline

• Summary and plans.


Main results

Operational implementation of the soil-merge• This should guarantee lower bias and mae for both T2M and TD2M in short range

COSMO-LEPS forecasts.

Time-series verification• ECMWF EPS changed substantially in the last year (introduction of EDA-based

perturbations) and it is hard to disentangle improvements related to COSMO-LEPS

upgrades from those due to better boundaries; nevertheless:– high values of BSS and ROC area for the probabilistic prediction of 12-h precipitation,

– lower outliers.


• Study in more detail the impact of the “new” ECMWF EPS on COSMO-LEPS.

• Develop new products for users (don’t keep them waiting for too long!), using

Fieldextra as much as possible.

• Test modifications to the clustering methodology.

• Increase vertical resolution (40 50 ML)?

• COSMO-LEPS@ 00UTC: implement it, finish it, put it operational; then, think

about generation of products from lagged ensembles.

• SOCHMEL: have a first prototype (inclusive of post-processing and dissemination)

by December for the future, need of computer time from COSMO countries!

• LAMEPS_BC project consider possible modifications to COSMO-LEPS suite.

• COSMO-LEPS for TIGGE-LAM (GRIB2 encoding).

Future plans

• Support calibration and verification.

• Carry on collaboration within research project (e.g. EFAS, SAFEWIND,

IMPRINTS, NURC, …).


Thank you !

European Conference on Applications of Meteorology / EMS annual meeting

12 – 16 September 2011, Berlin (Germany)

Session NWP4: Probabilistic and ensemble weather forecasting applications at short and very short ranges (including

nowcasting)

http://meetings.copernicus.org/ems2011


FROST-2014 vs SOCHMEL

1) Introduction to FROST-2014:

a) What is it?

b) What has to do with COSMO?

2) COSMO ensemble activities within FROST-2014:

a) introduction to SOCHMEL (the SOCHi-targeted Mesoscale EnsembLe system)

b) methodology;

c) phases of development;

d) planned activity.

3) Final remarks.


Important ingredients

1. Develop experience with probabilities.

2. Feedback on the top-priority products.

3. Snow analysis.

4. Soil-field initialisation.

5. Observations to assess the quality of the system.

6. Computer time.

7. Timeliness in product delivery.

8. …

More details in the plenary talk


Test data for LAMEPS Boundary Conditions


Proposed region for archiving LAMEPS BC data


Outline

• Introduction:

migration to the 7-km system.

COSMO-LEPS 10 km (old)

COSMO-LEPS 7 km (new)


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.


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.


Bias and rmse of T2M Ensemble Mean

Consider bias (the closer to zero, the better) and rmse (the lower the better).

Bias closer to zero (0.5 °C of decrease) and lower rmse for the 7-km suite. The improvement is not “massive”, but detectable for all forecast ranges, especially for day-time

verification. The signal is stable (similar scores for 1-month or 3-month verification).Need to correct T2M forecasts with height to assess the impact more clearly.


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).


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.


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).


COSMO-LEPS

16-MEMBER EPS

51-MEMBER EPS

tp > 1mm/24h

tp > 5mm/24h

Average values (boxes 0.5 x 0.5)MAM06

As regards AVERAGE precipitation above these two threshols, the 3 systems have similar performance.


ENSEMBLE SIZE REDUCTIONIMPACT EVALUATED ON CASE STUDIES (1)


ENSEMBLE SIZE REDUCTIONIMPACT EVALUATED ON CASE STUDIES (2)

Observed precipitation between 15-11-2002 12UTC and 16-11-2002 12 UTC

Piedmont case


2002111212 Piedmont

20 mm 150 mm

5 RMs

10 RMs

All 51


COSMO-LEPS

Real time products


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.


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


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


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

OBJECTIVE VERIFICATION OF COSMO-LEPS

COSMO observations


CLEPS EPS

Verification grid

OBS MASK


COSMO-LEPS

16-MEMBER EPS

51-MEMBER EPS

tp > 1mm/24h

tp > 5mm/24h

Average values boxes 0.5x0.5 deg3 sis


COSMO-LEPS

16-MEMBER EPS

tp > 1mm/24h

NOCC=610

NOCC=1195

tp > 5mm/24h

NOCC=2671

tp > 10mm/24h

ave 0.5


Maximum values boxes 0.5x0.5 deg

tp > 1mm/24h

tp > 5mm/24h

tp > 10mm/24h

COSMO-LEPS

16-MEMBER EPS

51-MEMBER EPS

3 sis


COSMO-LEPS

16-MEMBER EPS

tp > 20mm/24hNOCC=227

Average values boxes 0.5x0.5 deg


COSMO-LEPS NW

COSMO-LEPS W

tp > 1mm/24h

COSMO-LEPS weighting procedure

maximum values (boxes 0.5x0.5 deg)


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.


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”.


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.


COSMO-LEPS_10 (Old) vs COSMO-LEPS_7 (New)

• Deterministic verification of T2M ensemble mean

Variable: 2-metre temperature. Period: from June to November 2009. Forecast ranges: fc+6h, fc+12h, …, fc+132h. Scores: root-mean-square error, bias.

• Probabilistic verification of 12-hour cumulated precipitation

Variable:12h cumulated precipitation (18-06, 06-18 UTC). Period: from June to November 2009. Forecast ranges: fc 6-18h, fc 18-30h, …, fc 114-126h. Scores: ROC area, BSS, RPSS, Outliers. Thresholds: 1, 5, 10, 15, 25, 50 mm/12h.

Observations: SYNOP reports over either MAP D-PHASE region (450 reports/day) or the FULL-DOMAIN (1400 reports/day).

Method: nearest grid point; no-weighted fcst.


Bias and rmse of T2M Ensemble Mean

Consider bias and rmse for 3 months (24/5 24/8/2009) over MAPDOM (∼ 450 synop). T2m forecasts are corrected with height.

Bias closer to zero and lower rmse for the 7-km suite. Improvement is not “massive”, but detectable for all forecast ranges, especially for day-time

verification.Similar results over MAPDOM and over FULLDOM (not shown). The signal is stable (same scores also for 6-month verification).

---- OLD rmse (10 km)---- NEW rmse (7 km)—— OLD bias (10 km)—— NEW bias (7 km)


ROC area, BSS for 12-hour tp

Consider the event “10 mm of precipitation in 12 hours” for ROC area and BSS (from Jun to Nov 2009).

Better results for the 7-km suite, both for ROC area and BSS values.The impact is more evident for BSS.Reduction of 12-h cycle in 7-km runs. The improvement is detectable for all forecast ranges and for both MAPDOM and FULLDOM.

ROC area (both FULLDOM and MAPDOM)

BSS (both FULLDOM and MAPDOM)


COSMO-LEPS_10 (Old) vs COSMO-LEPS_7 (New)

• Deterministic verification of T2M ensemble mean

Variable: 2-metre temperature. Period: from June to November 2009. Forecast ranges: fc+6h, fc+12h, …, fc+132h. Scores: root-mean-square error, bias.

• Probabilistic verification of 12-hour cumulated precipitation

Variable:12h cumulated precipitation (18-06, 06-18 UTC). Period: from June to November 2009. Forecast ranges: fc 6-18h, fc 18-30h, …, fc 114-126h. Scores: ROC area, BSS, RPSS, Outliers. Thresholds: 1, 5, 10, 15, 25, 50 mm/12h.

Observations: SYNOP reports over either MAP D-PHASE region (450 reports/day) or the FULL-DOMAIN (1400 reports/day).

Method: nearest grid point; no-weighted fcst.


COSMO-LEPS (developed at ARPA-SIMC)

• 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, including Germany, Greece, Italy, Poland, Romania, Russia, 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 high-impact and localised weather events (heavy rainfall, strong winds, temperature anomalies, snowfall, …)

generation of COSMO-LEPS to improve the forecast of high-

impact weather in the short and early-medium range (up

to fc+132h)


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

a.montani; the cosmo-leps system. cosmo-leps: present status and developments andrea montani, d....

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