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10s Rainrate Statistics for the UK

10s Rainrate Statistics for the UK. Kevin Paulson Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire, OX11 0QX. Current Situation. Currently, ITU recommendations and RA license/power calculations are based on 1 minute rain rate statistics.

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10s Rainrate Statistics for the UK

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  1. 10s Rainrate Statistics for the UK Kevin Paulson Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire, OX11 0QX FSTWP 9/9/2002

  2. Current Situation • Currently, ITU recommendations and RA license/power calculations are based on 1 minute rain rate statistics. • Historically, one-minute raingauges were fast-response, links were long – introducing large spatial averaging. • Now 10s raingauges commercially available and short links of increasing importance. • Higher frequencies also mean that detecting mist mixed with heavy rain is more important. FSTWP 9/9/2002

  3. Temporal Spatial Averaging Temporal averaging point rain-rate over one-minute is roughly equivalent to spatial averaging over 1 Km. FSTWP 9/9/2002

  4. Problems with 1-minute statistics One-minute rain-rates will underestimate the incidence of high attenuation on short links (<1 Km) One-minute rain-rates smooth over short-term high attenuation events on longer links. One-minute sampling as restrictive as one-minute averaging FSTWP 9/9/2002

  5. First Order Statistics • Measure 10s rainrate distributions at various sites • More information on short outages • Better characterisation of short link (<1km) performance • Check and develop transformations between statistics measured at longer integration times FSTWP 9/9/2002

  6. Second Order Statistics • Measure 10 s rainrate time series at various sites • Synthetic Storm method allows terrestrial or satellite link time series to be synthesised • Develop/test fade duration/slope models • Develop/test fade mitigation techniques FSTWP 9/9/2002

  7. RAL Rapid Response Gauge Collector: standard UK Meteorological Office Mk IV Water formed into equi-volume drops which are counted optically Range 5->200 mm/hr in 1.4mm/hr steps Accuracy: ±10% Cost: £3000 FSTWP 9/9/2002

  8. ORG 815 Optical Scientific inc. ORG-815 FSTWP 9/9/2002

  9. ORG 815 Specification Rain rate dynamic range: 0.1 – 500 mm/hr Rain rate accuracy: about 5% Integration time: 10 s Precipitation type: rain/snow/mixed NOT effected by wind NO moving parts, very low maintenance Self-monintoring, self correcting Cost about £2000 Users: FAA, NASA, NOAA, US military, BAS, BMO ... FSTWP 9/9/2002

  10. Vaisala FD12P Detects 11 precipitation types Range 0-999 mm/hr with 30% accuracy One-minute integration time reporting every 15 s Cost: £7000 Used by UK Met. Off. FSTWP 9/9/2002

  11. Biral VPF-730 Made in UK. Rainrates: 0.015 - 250 mm/hr Errors: rainrate 10%, snowrate 20% Also measures visibility and precipitation type. Cost £7000 Typically 10-13 years operation without ANY maintenance! Used by Swedish Airports, FAA, USAF. ... FSTWP 9/9/2002

  12. Parsivel M300 Laser disdrometer designed by Voss Yields 10 s rainrate and WMO precipitation code, visibility, and particle size-velocity distribution. Rainrate derived from drop size-velocity distributions. Reported accuracy only for one-hour rainrates of 10%. Drops: 0.25 - 25 mm diameters Speed 0.1 - 20 m/s Cost: £16000 and up FSTWP 9/9/2002

  13. Proposal • Install and operate a selection of optical gauges and RAL rapid response gauges at several sites around the UK for several years. • This will yield 10s rainrate time series at each site and information on the performance, reliability and maintenance effort for each type of gauge. • Based on this experience, the experiment could be extended in both duration and number of sites to yield UK wide 10 s rain rate statistics. FSTWP 9/9/2002

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