THE NEW FRENCH OPERATIONAL CONVENTIONAL RADAR PRODUCTS

Pierre TabaryCentre de Météorologie Radar, Direction des Systèmes d’Observation, Météo France

pierre.tabary@meteo.fr

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