DMI / Sektion for Iskortlægning og Telemåling NORDIC WEATHER RADAR WORKSHOP R. S. Gill October...

DMI / Sektion for Iskortlægning og Telemåling

NORDIC WEATHER RADAR WORKSHOP

R. S. Gill

October 2002, Helsinki

DMI, Copenhagen


AGENDA

•Current state,

•Problems – what problems (?),

•Future Plans


Sindal

Rømø

Bornholm

Stevns

First and last (245 km) CAPPI layers – showing the extent of each Radar


No problems •but customer (weather services of DMI and the end users) request:wish to have EEC pseudo CAPPI product to be same as ERICSSON – to aid visual interpretation and improved composite product

Why are the Pseudo CAPPIs from ERICSSON and EEC different ?

Group set up : 5 people (Søren Overgaard, Lars Ørum Rasmussen, Lars Bøthum, Henrik Steen Andersen, and RSG )


NOTE:

•ERICSSON – ‘no/modest documentation’

•ERICSSON – deliver pseudo-CAPPI as product•EEC – CAPPI layers – DMI generate its own pseudo CAPPI usingnearest neighbour algorithm – this been tested it is fine.

Focus on:•Route correction – atmospheric and rain•Ring effect•Ab-normal Propagation problems•Signal interference

[EEC have been very helpful in resolving these ‘problems’.]


Ring effect


Ring effect

Stevns vejrradar d. 26.2.2002 kl. 11:40 UTC.

Rømø vejrradar d. 26.2.2002 kl. 9:20 UTC.


COMPOSITE problems – not new:

Data fra NORDRAD, 11.7.1996 kl. 17:00 UTC.


Anomalous propagation problems – not new


Route correction – atmospheric and rain attenuation

1. AtmosphericEEC : Katm(dB)= 0.017*r ERICSSON: Katm(dB)= 0.015*r

2.Rain Krain(dB/km)=cZd

EEC: c=6.9.e-5, d=0.67ERICSSON: c=1.172.e-4, d=0.649


Note:

ERICSSON given the following relation for rain attenuation

where ar is the attenuation due to rain in dB/km, L(F) and K(F) are functions of frequency and are given by the following expressions:

where F = log10(f/5), f is the frequency in GHz, is the radar return corrected for range and atmosphere. With the radar frequency used for the DMI radars (5.625 GHz) equation (2) gives for the frequency dependent constants L and K the following values:

L=-39.30948, K=0.649106

ZRAPFKFLrAar )()()()log(10

642.0149.0197.0)(

4.407.201.12)(2

2

FFFK

FFFL


Plots of attenuation in dB/km used in the Eriksson and EEC radars

0,00000

0,10000

0,20000

0,30000

0,40000

0,50000

0,60000

0,70000

0,0 20,0 40,0 60,0 80,0

Refractivity, Z(dBz)

Atte

ntua

tion

(dB/

km)

Eriksson

EEC

Shows a comparison between the attenuation of the radar signal due to precipitation between in Eriksson and EEC radars, in dB/km, for typical values of radar reflectivity, Z (dBz).


Difference between ERIKSSON and EEC radars after correction for atmosphere and precipitation against the same signal input,

Pzr in dBz

-1,00E+00

0,00E+00

1,00E+00

2,00E+00

3,00E+00

4,00E+00

0,00E+00

1,00E+01

2,00E+01

3,00E+01

4,00E+01

5,00E+01

6,00E+01

7,00E+01

Pzr, Input signal into the radars after range correction in dBz

ER

IKS

SO

N -

EE

C (d

Bz)

Eriksson - EEC at 10 km


eriksson - EEC at 100 km


Shows the difference between the Eriksson and EEC radars after corrections for atmosphere and precipitation against the same signal input in dBz, for a precipitation region of extent 10 km at 4 different ranges, 10 km, 50 km, 100 km and 150 km, from the radars.


Difference between ERIKSSON and EEC radars after correction for atmosphere and precipitation against the same signal input, Pzr in

dBz

-5,00E+00

0,00E+00

5,00E+00

1,00E+01

1,50E+01

2,00E+01

2,50E+01

0,00E+00 1,00E+01 2,00E+01 3,00E+01 4,00E+01 5,00E+01 6,00E+01

Pzr, Input signal into the radars after range correction in dBz

ERIK

SSO

N - E

EC (d

Bz)



eriksson - EEC at 100 km

Same as figure 3 except the precipitation region is of extent 100 km.


Possible explanation for the ring effect.

Generation of Pseudo-CAPPI from the CAPPI layers for Ericsson and EEC radars at DMI


Future plans:->Break down worries and acquiring spare parts with Ericsson radars (30 days ? repair period too long ! -)

•1. Replace all the current 3 Ericsson radars

•2. Replace all 3 but over a longer period

•3. Replace only Rømø then later (when funds available) replace Sindal, keep Bornholm as it is.

•4. Replace only the signal processors

•5. Replace the Micro VAX’s in Ericsson with PARTEC(Aerotech Telub) -?

[Tenderers have sent their proposals and are in the process being evaluated]

•6. Don’t do anything !

DMI / Sektion for Iskortlægning og Telemåling NORDIC WEATHER RADAR WORKSHOP R. S. Gill October...

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