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Published byJuliette Salyers Modified over 2 years ago

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

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

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

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DMI / Sektion for Iskortlægning og Telemåling 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 )

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DMI / Sektion for Iskortlægning og Telemåling 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’.]

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DMI / Sektion for Iskortlægning og Telemåling Ring effect

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

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

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

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DMI / Sektion for Iskortlægning og Telemåling Route correction – atmospheric and rain attenuation 1.Atmospheric EEC : K atm (dB)= 0.017*r ERICSSON: K atm (dB)= 0.015*r 2.Rain K rain (dB/km)=cZ d EEC: c=6.9.e-5, d=0.67 ERICSSON: c=1.172.e-4, d=0.649

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DMI / Sektion for Iskortlægning og Telemåling 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

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DMI / Sektion for Iskortlægning og Telemåling 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).

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DMI / Sektion for Iskortlægning og Telemåling 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.

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

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

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DMI / Sektion for Iskortlægning og Telemåling 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 !

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