1. NORDIC WEATHER RADAR WORKSHOP
R. S. Gill
October 2002, Helsinki
DMI, Copenhagen
DMI / Sektion for Iskortlægning og Telemåling

2. Problems – what problems (?), Future Plans
AGENDA
Current state,
Problems – what problems (?),
Future Plans
DMI / Sektion for Iskortlægning og Telemåling

3. Stevns
Sindal
Bornholm
Rømø
First and last (245 km) CAPPI layers – showing the extent of each Radar
DMI / Sektion for Iskortlægning og Telemåling

4. Why are the Pseudo CAPPIs from ERICSSON and EEC different ?
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 )
DMI / Sektion for Iskortlægning og Telemåling

5. ERICSSON – ‘no/modest documentation’
NOTE:
ERICSSON – ‘no/modest documentation’
ERICSSON – deliver pseudo-CAPPI as product
EEC – CAPPI layers – DMI generate its own pseudo CAPPI using
nearest 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’.]
DMI / Sektion for Iskortlægning og Telemåling

6. Ring effect
DMI / Sektion for Iskortlægning og Telemåling

7. Ring effect Stevns vejrradar d. 26.2.2002 kl. 11:40 UTC.
Rømø vejrradar d kl. 9:20 UTC.
DMI / Sektion for Iskortlægning og Telemåling

8. Data fra NORDRAD, 11.7.1996 kl. 17:00 UTC.
COMPOSITE problems – not new:
Data fra NORDRAD, kl. 17:00 UTC.
DMI / Sektion for Iskortlægning og Telemåling

9. Anomalous propagation problems – not new
DMI / Sektion for Iskortlægning og Telemåling

10. Route correction – atmospheric and rain attenuation Atmospheric
EEC : Katm(dB)= 0.017*r
ERICSSON: Katm(dB)= 0.015*r
2.Rain
Krain(dB/km)=cZd
EEC: c=6.9.e-5, d=0.67
ERICSSON: c=1.172.e-4, d=0.649
DMI / Sektion for Iskortlægning og Telemåling

11. ERICSSON given the following relation for rain attenuation
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= , K=
DMI / Sektion for Iskortlægning og Telemåling

12. 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).
DMI / Sektion for Iskortlægning og Telemåling

13. 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.
DMI / Sektion for Iskortlægning og Telemåling

14. Same as figure 3 except the precipitation region is of extent 100 km.
DMI / Sektion for Iskortlægning og Telemåling

15. Possible explanation for the ring effect.
Generation of Pseudo-CAPPI from the CAPPI layers for Ericsson and EEC radars at DMI
DMI / Sektion for Iskortlægning og Telemåling

16. Future plans: 1. Replace all the current 3 Ericsson radars
->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