Forecasting tropical cyclones with Aladin :

Transcription

Forecasting tropical cyclones with Aladin :
sensitivity to the physics and to the ocean surface
Ghislain Faure1 , F. Bouyssel2 , F. Taillefer2 , F. Orain3
1
2
Météo-France - LACy - La Réunion island
Météo-France - CNRM-GAME / GMAP - Toulouse
3
Météo-France - CMS - Lannion
20 TH ALADIN W ORKSHOP & HIRLAM ASM
K RAKOW, P OLAND , 13 - 16 A PRIL , 2010
20th Aladin Workshop & HIRLAM ASM (G. Faure)
Aladin-Réunion and tropical cyclones
1 / 24
OUTLINE
1
Numerical prediction of cyclones
Cyclones and numerical guidance
Aladin-Réunion
2
Sensitivity of TC intensity forecast
To air-sea exchanges
To microphysics
3
Conclusions
2 / 24
Next
1
Aladin-Réunion
2
To microphysics
3
Conclusions
3 / 24
Next
1
Aladin-Réunion
2
To microphysics
3
Conclusions
4 / 24
Tropical Cyclones : importance of the ocean
One of the most deadly natural threat
Cyclone wind speed > 120 km/h
Ocean is energy provider, a key for
intensity evolution
Usually long life systems (1-2 weeks)
Ocean-atm negative feedback
10-12% of worldwide activity, similar to North Atlantic
Wikimedia Commons
5 / 24
South West Indian Ocean basin
2000-2007 : 1800 deaths
10.5 tropical storms and 4.5
tropical cyclones (TC) a year
Météo-France La Réunion is
the WMO RSMC for this basin
(15 countries)
6 / 24
Numerical guidance
TC track
Impressive and sustained
improvements
Great help for forecasters
TC intensity
Poor numerical guidance
Models useful for environmental
conditions and trends
7 / 24
Next
1
Aladin-Réunion
2
To microphysics
3
Conclusions
8 / 24
Aladin over the South West Indian Ocean
Started on November 2006
Dedicated primarly to TC
forecasting (track and intensity)
Based on Aladin-France
Runs on Météo-France
supercomputer in Toulouse
8km L70 resolution, hydrostatic
~6000 x 3500 km
3D VAR
Coupling model : Arpege
Canari surface analysis
84h forecast (00Z,12Z)
4 assimilation runs/day
Final fields : 0°25 and 0°1
9 / 24
Specificity compared to Aladin-France : bogus
Why we need
pseudo-observations ?
90% of gridpoints over
ocean
Few satellite data
assimilated in cyclone
vicinity
Unrealistic TC
initialisation (position
and intensity)
10 / 24
11 / 24
11 / 24
Structure according to model resolution
Wind field of TC IVAN, February 2008
50°E
20080214 00h + 54h
ARPEGE (50 km) MF
50°E
IFS (25 km) ECMWF
Wind speed (m/s)
Wind speed (m/s)
21.62
27.80
25
20
20
15
15
10
10
5
5
2.190
50°E
0.7804
ALADIN REUNION (10 km) MF
50°E
Meso NH (4 km) Research model
Wind speed (m/s)
45.6
35
45
40
30
35
25
30
20
25
15
20
15
10
Wind speed (m/s)
37.97
10
5
5
0
0
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TC track forecasting
Track forecasting on average for
the 2 last seasons over South West
Indian Ocean :
1
IFS (worldwide leader)
2
Aladin-Réunion
GFDN
3
Skills differ for each system
For Gael, IFS runs were good
but westward bias
Aladin was almost perfect
13 / 24
Intensity errors for European models
14 / 24
Next
1
Aladin-Réunion
2
To microphysics
3
Conclusions
15 / 24
Next
1
Aladin-Réunion
2
To microphysics
3
Conclusions
16 / 24
SST analysis
SST analysis with Canari
Conventionnal obs. + NESDIS
SST field
Prescribed SST (no negative
feedback)
Debiased 2km satellite data
(Meteo-France CMS, MyOcean
european project)
I
I
Microwave channel for
cloudy regions
small scale features
SST anomalies impact TC intensity
Not in operations yet
17 / 24
SST analysis
SST analysis with Canari
Conventionnal obs. + NESDIS
SST field
Prescribed SST (no negative
feedback)
Debiased 2km satellite data
(Meteo-France CMS, MyOcean
european project)
I
I
Microwave channel for
cloudy regions
small scale features
SST anomalies impact TC intensity
Not in operations yet
17 / 24
Air-sea fluxes : ECUME parametrization
needed for TC wind conditions
February 2009 : more realistic
fluxes
ECUME is based on a bulk algorithm
Multi-campaign calibration of neutral exchange
coefficients
Adjustements for strongest winds (saturation or
even decrease)
As expected, an important decrease of energy provided to IVAN
18 / 24
Air-sea fluxes : ECUME parametrization
needed for TC wind conditions
February 2009 : more realistic
fluxes
ECUME is based on a bulk algorithm
Multi-campaign calibration of neutral exchange
coefficients
Adjustements for strongest winds (saturation or
even decrease)
As expected, an important decrease of energy provided to IVAN
18 / 24
Extreme sensitivity
both on air-sea fluxes and SST
OPER : Louis + low
resolution SST
ECUME : ECUME + low
resolution SST
ECUME + SST : ECUME
+ high resolution SST
19 / 24
Extreme sensitivity
OPER : Louis + low
resolution SST
ECUME : ECUME + low
resolution SST
ECUME + SST : ECUME
19 / 24
Extreme sensitivity
OPER : Louis + low
resolution SST
ECUME : ECUME + low
resolution SST
ECUME + SST : ECUME
19 / 24
Next
1
Aladin-Réunion
2
To microphysics
3
Conclusions
20 / 24
Rare but strong overintensifications
Aladin-Réunion runs on 2009 02 03 00Z (GAEL)
995
Preliminary results !
Central pressure (hPa)
970
Unrealistic deepening (world record
class)
945
32 hPa difference when increasing
snow fall speed from 0.6 to 0.9 m/s
920
Still too intense ...
895
but realistic structure
870
Work under progress : non
constant speed, other sensitivities
0
6
12 18 24 30 36 42 48 54 60 66 72 78 84
Forecast lead time (h)
OBS
0.6 m/s snow
fall speed
21 / 24
Aladin-Réunion runs on 2009 02 03 00Z (GAEL)
995
Central pressure (hPa)
970
class)
945
920
895
870
0
6
12 18 24 30 36 42 48 54 60 66 72 78 84
Forecast lead time (h)
OBS
0.6 m/s snow
fall speed
0.9 m/s snow
fall speed
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class)
21 / 24
Next
1
Aladin-Réunion
2
To microphysics
3
Conclusions
22 / 24
A useful model
Good abilities for TC forecasting
Realistic TC structure from the analysis
Good scores across years for track and intensity
Improvements of intensity forecast skills
However a few cases of overintensification
But also for tropical weather
Good analyses, even compared to global models ones (4D Var)
Added value for island local effect forecasts
Prospects
Aladin 3D Var over each overseas French territory
SWICE : TC campaign in South Western Indian Ocean
Higher resolution (structure, processes, impacts)
23 / 24
The end
Thank you for your attention
Any question ?
24 / 24
The end
Thank you for your attention
Any question ?
24 / 24

Forecasting tropical cyclones with Aladin :

Transcription

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