Upload
yamal
View
32
Download
0
Embed Size (px)
DESCRIPTION
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. - PowerPoint PPT Presentation
Citation preview
FSTWP 9/9/2002 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.