High-resolution Non-hydrostatic Numerical High-resolution Non-hydrostatic Numerical Weather Prediction of Mediterranean torrential Weather Prediction of Mediterranean torrential
rain eventsrain events
Véronique DUCROCQ, Cindy LEBEAUPIN, Olivier NUISSIER, Didier RICARD,
Hervé GIORDANI
CNRM/GAMEMétéo-France & CNRS
World Weather Research Program Symposium on Nowcasting and Very Short Range Forecasting, Toulouse, 5-9 Sept. 2005
Algiers, 10 Nov. 2001~260 mm in less than 24 hours>700 deaths, 4 billion € damages(Hamadache et al, 2002)
Gandia, 3 Nov. 1987 ~800 mm in 24 hours(Fernandez et al, 1995)
Vaison La Romaine, 22 Nov. 1992~300 mm in 24 hours>50 deaths, 1 billion € damages(Sénési et al, 1996)
Piedmont, 4-5 Nov. 1994~300 mm in 36 hours> 60 deaths, 12 billion € damages(Buzzi et al, 1998)
Spain
Italy
France
Mediterranean
Sea
Western Mediterranean region is prone to torrential rain events © Midi-Libre
Algiers, 10 Nov. 2001~260 mm in less than 24 hours>700 deaths, 4 billion € damages(Hamadache et al, 2002)
Gandia, 3 Nov. 1987 ~800 mm in 24 hours(Fernandez et al, 1995)
Vaison La Romaine, 22 Nov. 1992~300 mm in 24 hours>50 deaths, 1 billion € damages(Sénési et al, 1996)
Piedmont, 4-5 Nov. 1994~300 mm in 36 hours> 60 deaths, 12 billion € damages(Buzzi et al, 1998)
Spain
Italy
France
Mediterranean
Sea
Western Mediterranean region is prone to torrential rain events © Midi-Libre
Piedmont, 4-5 Nov. 1994~300 mm in 36 hours> 60 deaths, 12 billion €(Buzzi et al, 1998)
Spain
Italy
France
Mediterranean
Sea
For France, the southeastern France (Massif Central) is a threatened regionNumber of days withdaily precipitation > 200 mm from 1958 to 2000 for Southern France
Mas
sif
Cent
ral
Alps
Pyrenees
Toulouse
Gardon d’Anduze Watershed (545 km2)
Discharges
hou
rly r
aig
au
ge a
nd
rad
ar
rain
fall d
ep
ths
over
the w
ate
rsh
ed
660 700 740 780
Lam bert II é tendu (km )
1840
1880
1920
1960
2000
Lam
bert
II é
tend
u (k
m)
M t Aigoual
M ontpellier
Privas
M ende
M illau
Le Puy
Valence
Alès
M t M ézenc
M t Lozère
0
200
400
600
800
1000
1200
1400
1600
m ètres
HéraultVidourle
Gard
GardonsCèze
ArdècheChassezac
Eyrieux
Rhô
ne
A lot of rivers have their sources in the Massif Central Steep slopes of the rivers and small catchments increasing the speed of the streamflow
*AnduzeAnduze
Rainfall peak
LTHE
Flow peak
~6 h
The heavy precipitation touch areas that have a high-level flash-flood risk due to orography : small catchments (500km2-2000 km2) with fast responses to rain showers
Need for very short range model forecasts to provide longer lead times to prepare for flash-flooding and secure people.
High Conditional Convective instability
A very moist Low-Level Jet
Steep orography to
trigger/enhance the
convection
Slow progressing synoptic patterns
Quasi-stationary high-geopotentials over Central Europe
Mesoscale PV
anomalies
Synoptic forcing and topography forcing (reliefs + Mediterranean sea) increase the predictability of flash-flood driven thunderstorms.
Synoptic conditions propitious to torrential rain events
In most cases, the forecast of propitious conditions at synoptic scale allows to forecast the occurrence of an heavy precipitation event over the region, however it is still difficult to forecast : - the magnitude (normal or extreme heavy precipitation event) - the precise location (at a scale of less than 100 km).
100km
?
Vigilance map
High Conditional Convective instability
A very moist Low-Level Jet
Steep orography to
trigger/enhance the
convection
Slow progressing synoptic patterns
Quasi-stationary high-geopotentials over Central Europe
Mesoscale PV
anomalies
Synoptic forcing and topography forcing (reliefs + Mediterranean sea) increase the predictability of flash-flood driven thunderstorms.
Synoptic conditions propitious to torrential rain events
In most cases, the forecast of propitious conditions at synoptic scale allows to forecast the occurrence of an heavy precipitation event over the region, however it is still difficult to forecast : - the magnitude (normal or extreme heavy precipitation event) - the precise location (at a scale of less than 100 km).
The aim of the study is to examine the capability of a high-resolution non-hydrostatic model to forecast torrential rain events at very short range (in view of the next generation operational model AROME).
emphasis on the sensitivity to initial conditions (atmosphere and surface)
Date Type Maximum of 24-h rainfall
13-14/10/1995 quasi-stationary MCS ~ 250 mm
3-4 /10/1995 quasi-stationary MCS ~ 200 mm
12-13/11/1999The Aude extreme flash-flood event ~30deaths, 3 millions € damages
quasi-stationary MCS ~ 550 mm
6-7/10/2001 quasi-stationary MCS ~350 mm
8-9/09/2002 The Gard extreme flash-flood event~20 deaths, 1.2 billion € damages
quasi-stationary MCS and front ~ 700 mm
3/12/2003The 3rd day of a major Rhône flooding
quasi-stationary frontal system with embedded convection
~ 180 mm
including cases of
- quasi-stationary back-building MCS
- quasi-stationary frontal systems
The case studies
Gard flash-flood, 2002
Rhône flooding 3 Dec.2003
Torrential rain events over Southeastern France
Performed with the non-hydrostatic MESO-NH model (Lafore et al, 1998)
Two-way grid-nesting (Stein et al, 2000) :
•Domain 1 ~ 10 km•Domain 2 ~ 2.5 km (centred on the convective event)
Characteristics of the high-resolution simulations
Almost the same physical package as in AROME, including a bulk microphysic parameterization (Pinty et Jabouille, 1998, Caniaux,
1994) with 6 prognostic water variables : water vapour, cloud water rainwater, primary ice, graupel and snowThe convection is parameterized following the Kain and Fritsch parameterization for the 10-km domain whereas convection is explicitly resolved for the 2.5 km domain (no deep convection scheme).
10-km domain
2.5-km domain
~500-600 km
Initial conditions provided either by a large scale analysis (ARPEGE/IFS) or by a mesoscale analysis following Ducrocq et al, 2000 (objective analysis of mesonet surface observations, qv, qr and qs bogussing based on radar and satellite data)
>100 mm
>75 mm>50 mm>30 mm>20 mm
>10 mm
>5 mm>2 mm>1 mm
Rhône flood event (3 December 2003)
9-h accumulated precipitation from 03 UTC to 12 UTC, 3 Dec. 2003
Initial conditions : large scale ARPEGE analysis at 00 UTC, 3 Dec. 2003
Raingauge data 2.4 km MESO-NH forecast
100 km
+Nîmes
+Nîmes
Observations
Nîmes radar
Raingauges
Same Initial Conditions (ARPEGE analysis12UTC, 08/09/02) and same boundary conditions (3-hourly ARPEGE forecast)
+
12-h accumulated precipitation from 12 UTC, 8 Sept to 00 UTC, 9 Sept 2002
Gard flash-flood (8-9 Sept.2002)Aladin (9.4 km)operational forecast
MESO-NH (2.5km)
100 km
+Nîmes
+Nîmes
Observations
Nîmes radar
Raingauges
Initial Conditions : ARPEGE analysis12UTC, 08/09/02
+
MESO-NH (2.5km)
12-h accumulated precipitation from 12 UTC, 8 Sept to 00 UTC, 9 Sept 2002
Initial Conditions : Ducrocq et al (2000) Initialisation12UTC, 08/09/02
100 km
+
Gard flash-flood (8-9 Sept.2002)
SST for the Aude flash-flood case :
SST=17.8°C SST=17.4°C
- In-situ buoys and ships SST data analysis (ARPEGE)
- High-resolution satellite SST (AVHRR/NOAA )
Sensitivity to the Sea Surface Temperature of the Mediterranean Sea
- Warming [Cooling] of the ARPEGE analysis by 1.5°C (SST analysis error range)
Several SST fields tested :
Initial cond.:ARPEGE analysis, 12 UTC, 12 Nov. 1999
SST ARPEGE SST AVHRR
SST ARPEGE -1.5°CSST ARPEGE +1.5°C
18-hour accumulated precipitation from 12 UTC, 12 Nov. 1999 to 06 UTC, 13 Nov. 1999
Max:303mm Max:296mm
Max obs.:
485mm
Max:368mm Max:274mm
100 km
(mm)
Several cases of flash-flood have been simulated with the high-resolution non-hydrostatic MESO-NH model
get an insight into the capabilities of the next-generation operational high-resolution NWP systems, including the future Météo-France AROME model, to forecast Mediterranean torrential rain events.
In all the cases, the 2.5 km simulations improve the very short range QPF with respect to the current operational models. Forecast rainfall amounts are close to the observed ones for normal flash-flood event, but still underestimated for extreme events.
The improvement in location and in intensity is however in most cases a tribute to the mesoscale initial conditions. Dynamical adaptation from large scale analyses in most cases is not sufficient : mesoscale data assimilation improves rainfall forecast even in cases with strong synoptic forcing.
Primary importance of the assimilation of observations in the boundary layer (mesoscale surface observations) : cold pool, low-level convergence line, low-level moisture flow,
The SST acts to modulate the magnitude and location of the convective system : A significant dependency on the mean value of the SST over the Western Mediterranean basin, but a weak one to the mesoscale patterns of the SST field. also a role of the parameterization of the sea-atmosphere fluxes (not shown here).
Errors in location of the same order than the size of the small/medium watersheds plead in favor of a probabilistic post-processing of the high-resolution forecasts for hydrological applications.
Conclusion and outlook
Thank you for your attention
ARPEGE+1.5° ARPEGE
ARPEGE+3° ARPEGE-1.5° ARPEGE-3°
AVHRR
Aude flash-flood (12-13 Nov. 1999)
Synthetic infrared METEOSAT radiances at 00 UTC, 13 Nov. 1999 from 12-h MESO-NH forecasts using various initial SST fields
Initial conditions : large scale ARPEGE analysis at 12 UTC, 12 Nov. 1999