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Chilbolton Facility for Atmospheric and Radio Research Rain Masking A note on Capacitative Rain Sensors John Goddard Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
Rain MaskingA note on Capacitative Rain Sensors
John Goddard
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
• Investigation into use of simple rain detectors to flag onset and cessation of rain• Valuable for quality control of radar vertical profiling
• Comparison of sensors was described at 3rd Cloudnet meeting• Included
• tipping bucket raingauges• drop counting raingauges• disdrometers• optical sensors
• Conclusions were:
• Distrometer and Optical gauge - both good indicators of precipitation onset• Drop counting gauges lag these by 2-5 minutes
(maybe depending on how wet the collector has remained since the last event)• Tipping bucket gauge - not useful for this purpose
- lags of tens of minutes in weak precipitation- 2 factors, collector wetting and bucket capacity
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
• Action 3.1 from the meeting was to investigate capacitative sensors • may be cost effective solution?
• Two types of capacitative sensor have been deployed at Chilbolton• primarily to assist rain data quality control• eliminating calibration spikes, etc
1. Vaisala DRD11A Rain Detector
2. Sontay WD-RS Rain sensor
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
DRD11A Rain DetectorWD-RS Rain Sensor
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
Both instruments have heated surfaces• eliminates fog and dew• reduces effects of snow
(not tested at Chilbolton yet!)
Both instruments use ttl voltage levels(0 or 5V for rain/no rain)
DRD11A has additional delay circuitry giving 2 minute interval between drops before setting the no rain state
DRD11A interface was straight forwardWD-RS required additional interface circuit
DRD11A deployed
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
Example from 1 October 2003
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
Expanded view
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
End of the event
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
Blip
Chilbolton Facilities for Atmospheric and Radio Research
Chilbolton Facility for Atmospheric and Radio Research
Conclusions
Instruments have similar characteristics
DRD11A is easier to install• it is appears to be more sensitive (over-sensitive?)
WD-RS sensor costs ~€170(www.sontay.com)
DRD11A sensor costs ~€740(www.vaisala.com)
Chilbolton Facilities for Atmospheric and Radio Research
