Post on 16-Jul-2020
Convection-permittingensemble simulationsandMediterranean HPEs
Benoît Vié1
Olivier Nuissier1
Véronique Ducrocq1
1Météo-France - CNRM
1 August 2011
Why do we need a convection-permitting EPS?
Z500
925 hPa wind925 hPa θ
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D1
Why do we need a convection-permitting EPS?
◮ Convection-permitting,non-hydrostatic NWP models producevery realistic forecasts
◮ Realistic 6= Real
◮ Runoff forecasts are very sensitive tothe rainfall forecasts, especially forsmall and steep mountainouswatersheds
◮ EPSs are one method to evaluate theforecast uncertainty
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D1
The AROME model (late 2008)
◮ Non-hydrostatic
◮ 2.5 km horizontal grid spacing
◮ 41 vertical levels
◮ 3D-VAR data assimilation scheme
◮ Bulk microphysics parameterization,6 prognostic water variables: watervapour, cloud water, rainwater,primary ice, graupel and snow(Pinty and Jabouille, 1998, Caniaux,1994)
FRANCE
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D2
AROME forecasts and uncertainty12 UTC06 UTC00 UTC 18 UTC 00 UTC 06 UTC 12 UTC
ALADIN
AROME
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(2.5 km)
ALADIN & AROME data assimilation cycle
24-h forecasts
LBCs ICs
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D3
AROME forecasts and uncertainty12 UTC06 UTC00 UTC 18 UTC 00 UTC 06 UTC 12 UTC
ALADIN
AROME
(10 km)
(2.5 km)
ALADIN & AROME data assimilation cycle
24-h forecasts
LBCs ICs
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D3
AROME forecasts and uncertainty12 UTC06 UTC00 UTC 18 UTC 00 UTC 06 UTC 12 UTC
ALADIN
AROME
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(2.5 km)
ALADIN & AROME data assimilation cycle
24-h forecasts
LBCs ICs
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D3
The Ensemble experiments
AROME-PEARP◮ Each AROME assimilation cycle uses LBCs from one
PEARP (global, short range ensemble) member
AROME-PERTOBS◮ Unique LBCs from the deterministic large scale forecast◮ Each AROME assimilation cycle uses randomly perturbed
observations
◮ The AROME-PEARP ensemble samples the uncertaintyon synoptic-scale LBCs and initial conditions
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D4
The Ensemble experiments
AROME-PEARP◮ Each AROME assimilation cycle uses LBCs from one
PEARP (global, short range ensemble) member
AROME-PERTOBS◮ Unique LBCs from the deterministic large scale forecast◮ Each AROME assimilation cycle uses randomly perturbed
observations
◮ The ensemble data assimilation technique is known tosample the analysis error quite well (Berre et al., 2006)
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D4
The Ensemble experiments
AROME-PEARP◮ Each AROME assimilation cycle uses LBCs from one
PEARP (global, short range ensemble) member
AROME-PERTOBS◮ Unique LBCs from the deterministic large scale forecast◮ Each AROME assimilation cycle uses randomly perturbed
observations
AROME-COMB◮ LBCs from one PEARP member◮ Assimilation of randomly perturbed observations
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D4
Evaluation period
31 (18) days◮ 6 October 2008 -> 5 November 2008 (31 days)◮ 15 October 2008 -> 1 November 2008 (18 days)
◮ 20 October 2008observed daily precipitation
◮ 1-2 November 2008observed daily precipitation
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D5
Results
Vié, B., O. Nuissier and V. Ducrocq, 2011: Cloud-resolving ensemble simulations ofMediterranean Heavy Precipitating Events: Uncertainty on initial conditions and lateralboundary conditions, MWR, 139:403-423
◮ The impact of uncertainty on LBCs rapidly overcomes the impact of uncertaintyon ICs (after around 12 h in our configuration)
◮ The relative impact of ICs and LBCs depends on the meteorological situation
◮ The spread in the AROME-PEARP ensemble represents a temporal or spatialuncertainty better (it has a wider geographical extent)
◮ Promising precipitation scores, despite the underdispersion for low-levelparameters
◮ The combination of both sources of uncertainty in the AROME-COMB ensembleimproves the performance
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D6
Selective perturbation of observations
◮ Focus on important low-level parameters for the HPEs, as identified throughcase studies (O. Nuissier, V. Ducrocq) and idealized simulations (E. Bresson)
wind speed
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00 UTC 31 Oct. 2010, 12-h accumulated precipitation, AROME forecasts
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D7
Taking model errors into consideration
With collaboration from É. Richard, S. Fresnay and A. Hally, Laboratoire d’Aérologie,Toulouse, France.
◮ Perturbation of 3 microphysical tendencies:
◮ autoconversion◮ accretion◮ evaporation
◮ No effect on probabilistic scores
◮ For some special cases, changes both the intensity and position of theprecipitating system
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D8
Taking model errors into consideration
20 Oct. 2008, 00 UTC + 12 h, θv (colours), CWC (black), RWC (gray)
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D9
Taking model errors into consideration
20 Oct. 2008, 00 UTC + 15 h, θv (colours), CWC (black), RWC (gray)
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D9
Taking model errors into consideration
20 Oct. 2008, 00 UTC + 18 h, θv (colours), CWC (black), RWC (gray)
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D9
Ensemble spread
◮ Ensemble combining all the three sources of uncertainty◮ Average over 18 days◮ Vertical profiles of ensemble spread and RMSE for temperature
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D10
Conclusions & prospects
Vié, B., O. Nuissier and V. Ducrocq, 2011: Cloud-resolving ensemble simulations ofMediterranean Heavy Precipitating Events: Uncertainty on initial conditions and lateralboundary conditions, MWR, 139:403-423
◮ Uncertainty on LBCs has the strongest impact on the CPM forecasts
◮ Focus on the predictability of HPEs or design a generic EPS?
◮ Better sampling of model errors (e.g. stochastic physics, F. Bouttier)
◮ Introducing perturbations of the low-level conditions (surface fields, orography...)
◮ Select a few representative members from a global ensemble (O. Nuissier)
◮ Perform a hydrometeorological evaluation of the ensemble forecasts within theframework of the MEDUP project, article to be submitted in NHESS (incollaboration with G. Molinié, LTHE, and B. Vincendon)
◮ Sept-Oct 2013: Special Observing Period of HyMeX
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D11
Conclusions & prospects
Vié, B., O. Nuissier and V. Ducrocq, 2011: Cloud-resolving ensemble simulations ofMediterranean Heavy Precipitating Events: Uncertainty on initial conditions and lateralboundary conditions, MWR, 139:403-423
◮ Uncertainty on LBCs has the strongest impact on the CPM forecasts
◮ Focus on the predictability of HPEs or design a generic EPS?
◮ Better sampling of model errors (e.g. stochastic physics, F. Bouttier)
◮ Introducing perturbations of the low-level conditions (surface fields, orography...)
◮ Select a few representative members from a global ensemble (O. Nuissier)
◮ Perform a hydrometeorological evaluation of the ensemble forecasts within theframework of the MEDUP project, article to be submitted in NHESS (incollaboration with G. Molinié, LTHE, and B. Vincendon)
◮ Sept-Oct 2013: Special Observing Period of HyMeX
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D11
Conclusions & prospects
Vié, B., O. Nuissier and V. Ducrocq, 2011: Cloud-resolving ensemble simulations ofMediterranean Heavy Precipitating Events: Uncertainty on initial conditions and lateralboundary conditions, MWR, 139:403-423
◮ Uncertainty on LBCs has the strongest impact on the CPM forecasts
◮ Focus on the predictability of HPEs or design a generic EPS?
◮ Better sampling of model errors (e.g. stochastic physics, F. Bouttier)
◮ Introducing perturbations of the low-level conditions (surface fields, orography...)
◮ Select a few representative members from a global ensemble (O. Nuissier)
◮ Perform a hydrometeorological evaluation of the ensemble forecasts within theframework of the MEDUP project, article to be submitted in NHESS (incollaboration with G. Molinié, LTHE, and B. Vincendon)
◮ Sept-Oct 2013: Special Observing Period of HyMeX
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D11
Conclusions & prospects
Vié, B., O. Nuissier and V. Ducrocq, 2011: Cloud-resolving ensemble simulations ofMediterranean Heavy Precipitating Events: Uncertainty on initial conditions and lateralboundary conditions, MWR, 139:403-423
◮ Uncertainty on LBCs has the strongest impact on the CPM forecasts
◮ Focus on the predictability of HPEs or design a generic EPS?
◮ Better sampling of model errors (e.g. stochastic physics, F. Bouttier)
◮ Introducing perturbations of the low-level conditions (surface fields, orography...)
◮ Select a few representative members from a global ensemble (O. Nuissier)
◮ Perform a hydrometeorological evaluation of the ensemble forecasts within theframework of the MEDUP project, article to be submitted in NHESS (incollaboration with G. Molinié, LTHE, and B. Vincendon)
◮ Sept-Oct 2013: Special Observing Period of HyMeX
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D11
Questions ?
The AROME-PEARP experiment
(x11) (x11) (x11)
12 UTC06 UTC00 UTC 18 UTC 00 UTC 06 UTC 12 UTC
PEARP
ALADIN
AROME
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(10 km)
(2.5 km)
(x11)
(x11)
AROME & ALADIN Data Assimilation Cycle
24-h forecasts
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D13
The AROME-PERTOBS experiment
12 UTC06 UTC00 UTC 18 UTC 00 UTC 06 UTC 12 UTC
ALADIN
AROME
(10 km)
(2.5 km)
AROME(2.5 km)
&
(x10)
ALADIN & AROME data assimilation cycle
24-h forecasts
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D14
Example on a case study: 1-2 Nov. 2008
AROME-PEARP AROME-PERTOBS AROME-COMB
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D15
Example on a case study: 1-2 Nov. 2008
AROME-PEARP AROME-PERTOBS AROME-COMB
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D15
Example on a case study: 1-2 Nov. 2008
AROME-PEARP AROME-PERTOBS AROME-COMB
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D15
Example on a case study: 1-2 Nov. 2008
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AROME-PEARP
24h accumulatedprecipitation,12 UTC 2 Nov. 2008
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D16
Example on a case study: 1-2 Nov. 2008
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24h accumulatedprecipitation,12 UTC 2 Nov. 2008
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D17
Example on a case study: 1-2 Nov. 2008
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AROME-COMB
24h accumulatedprecipitation,12 UTC 2 Nov. 2008
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D18
Case study: 20 Oct. 2008
AROME-PEARP AROME-PERTOBS AROME-COMB
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D19
Case study: 20 Oct. 2008
AROME-PEARP AROME-PERTOBS AROME-COMB
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D19
Case study: 20 Oct. 2008
AROME-PEARP AROME-PERTOBS AROME-COMB
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D19
Case study: 20 Oct. 2008
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14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D20
Case study: 20 Oct. 2008
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AROME-PERTOBS
24h accumulatedprecipitation,12 UTC 2 Nov. 2008
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D21
Case study: 20 Oct. 2008
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AROME-COMB
24h accumulatedprecipitation,12 UTC 2 Nov. 2008
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D22
Precipitation: ROC and reliability diagram
Relative Operating Characteristics◮ Probability Of Detection against False Alarm Rate◮ The upper the curve is, the better the resolution of the
ensemble is
Reliability diagram◮ Observed frequency
againstforecast probability
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AROME-PEARPAROME-PERTOBS
AROME-COMB
RR24 ≥ 0.5 mm
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RR24 ≥ 10 mm
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AROME-PEARPAROME-PERTOBS
AROME-COMB
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D23
Precipitation: Ensemble spread
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AROME-PEARPAROME-PERTOBS
AROME-COMB
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D24
Ensemble spread for 925hPa wind speed
Rank histograms: a U-shaped histogram shows ensemble underdispersion
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3h
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AROME-COMB
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AROME-COMB
6h
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AROME-COMB
12h
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24h
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RMSE vs. Ensemble spread
14th AMS conference on Mesoscale Processes, 1 August 2011, LA | B V, O N, V D25