the new french operational conventional radar products pierre tabary centre de météorologie radar,...
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THE NEW FRENCH OPERATIONAL CONVENTIONAL RADAR PRODUCTS
Pierre TabaryCentre de Météorologie Radar, Direction des Systèmes d’Observation, Météo France
The French operational radar network In 2006 : 24 radars of different wavelength (8 S-band, 16 C-band) and type (GEMATRONIK, THOMSON, …)
All radars are equipped with the same « home-made » radar processor (CASTOR2, See the contribution of Parent-du-Châtelet et al. to the 2001 Radar Conference)
Doppler processing (« staggered-PRT », See Tabary et al., 2005, JAOT) and products are gradually introduced all radars will be Doppler by 2008;
Polarimetry is currently tested on the Trappes (Paris) radar (See Poster 4.13 by Gourley et al.) 8 polarimetric radars by the end of 2006 ?
Current operational productsRainfall intensity maps ( Surveillance, Nowcasting, Aviation safety, …)
Single radar (Bollène) Composite (France)
1 km² x 5 minutes;
Constant pseudo-CAPPI composition;
Dynamical ground-clutter suppression;
No VPR nor partial beam-blocking correction;
Marshall-Palmer Z-R relationship;9 September 2002 09.00 UTC
Radar QPE ( Hydrology)
Single radar only;
Available every 15 minutes;
No radar – rain gauge real-time adjustment;
24h accumulation – Toulouse radar – Start = 16 April 2005 06.00 UTC
The new conventional radar products
Radar QPE Hydrology
Pixel-by-pixel composition (Joss and Lee 1995);
VPR correction (Kitchen et al. 1994, Andrieu et al. 1995)
Partial beam blocking correction (orogenic : Delrieu et al. 1995 and non-orogenic : use of long-term accumulations);
Enhanced frequency : 5 minutes ( Urban applications);
Systematic generation of quantitative quality indexes;
Single radar
Composite
Radar « Detection product » Nowcasting
Maximum reflectivity along the vertical;
Bright-band correction only;
Partial beam blocking correction ;
Systematic generation of detailled quality indexes;
Single radar
Composite
?
RR3
Unshielded, not in the bright-band, but high
RR2
unshielded, not too high, but in the bright band
RR1
low but shielded
1
2
3
Courtesy of JJ Gourley (NSSL)
RR1 RR2 RR3
RR1corr
1
RR2corr
2
RR3corr
3
Correction for VPR, partial beam-blocking, ground-clutter and advection
RRbest = iiRRicorr / ii
best=MAXi(i)Weighted linear combination
The new radar QPE
Try to get the best surface estimation from the ith tilt
Assign a weight to each estimation
The VPR correctionKitchen et al. 1994; Kitchen 1996; Andrieu et al. 1995, Fabry and Zawadzki 1995
Simulate – for each VPR candidate - the expected radar observations (ratio
curves)
Simulate VPR candidates
The four parameters can only take a limited number
of predetermined, climatology-based values
Observed radar measurements (ratio
curves)
Optimal VPR
Correction / extrapolation down to ground-level
A conceptual four-parameter VPR
3dB beamwidth
A guess is provided by the model
Comparison of radar-derived Freezing Level Heights with radiosonde 0°C (dry and wet bulb) heights
Illustration of Single-radar QPE24 h accumulation – 20050206 - Opoul radar
Old QPE (HYDRAM) New QPE (PANTHERE) Quality indexes
0 (purple) = excellent
255 (red)= badProposed (empirical) formula for the quality index:
= exp[-(h-hterrain) / h0] x (1-T/100)1/1.6
0 if ground-clutter or strongly shielded (T > 70%)
with : h = altitude of the beam, h0 = 1 km and T = occultation rate (%)
Are the proposed quality indexes relevant ?Is there a correlation between radar vs. rain gauge scores and the quality indexes ?
15 episodes included. Each curve corresponds to one episode. The dotted curve is the mean
Nash criterion
Corr. coefficient
0 (good) Quality indexes 200 (bad) 0 (good) Quality indexes 200 (bad)
Illustration of composite QPE24 h accumulation – 20050206 – 7 radars of Southern France
Composite QPE
Composite quality index map
Rcomposite = jradar Rjradar / jradar
composite = MAXjradar(jradar)
Applications
NWP QPF verification;
Radar – rain gauge adjustment;
Assimilation in hydrologic models;
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
The Single-radar and composite « detection product »
Attenuation by rain Partial beam blocking
Altitude
Status of the pixelBright band correction
3-level quality index
Advection duration
Maximum reflectivity
Thank you