Why The Need For HCN-M ?

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Why The Need For HCN-M ?

• More Accurate Data Through
• Redundant Sensors
• Near Real Time Diagnostics
• Time Resolution of Five Minutes vs The Current
  Daily

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Human Interaction With Weather Observations Has
Been The Backbone Of The Historical Data Sets For
More Than 100 Years
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Temperature Measurements
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Louvered Shelter For Ventilation Of Temperature
Sensors And Protection From Direct Solar And
Terrestrial Radiation
Used By Both Primary And Cooperative Stations For
More than 100 Years
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Redundant sensors, more than one thermometer in
each shelter
Minimum Thermometer
Maximum Thermometer
Thermograph
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Primary Weather Stations Were Also Equipped With
Two Additional Matched Thermometers For
Determining The Dew Point Temperature And
Relative Humidity
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Redundancy Of Temperature Measurement Was Lost In
The 1980s With Conversion To A Single Automated
Electronic Sensor Called The MMTS.
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Lightning, the worst nightmare for electrically
operated temperature sensors. Those same
electronic temperature sensors are also subject
to salt air corrosion, and insect nests. (See
next slide)
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Data From An MMTS Temperature System At A
Cooperative Station
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Ventilation problems and slippage of the
mechanically driven clutch read-out of the
automated temperature sensor at the Asheville
Airport compromised the readings from the site
for more than 20 years. (See Next Slide)
Even Primary Airport Weather Stations Are Not
Exempt From Single Sensor Failures
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Modernization Of The Equipment At The HCN Test
Sites Uses The Proven Methodology Of The
Past,Redundant Sensors
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AL Greensboro HCN-M (County Jail) 32.7 N 87.6 W
273 March 16, 2007
Geonor All-Weather Precipitation Gage With Three
Independent Sensors And Protecting Wind Fence
Three Temperature Sensors in One Shield Equipped
With Two Fans
Solar Panels to Power the Station
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Fan Ventilation Rate (R/S)
Temperature Traces of The Three Thermometers
Back-Up Fan
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Precipitation Measurements
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Snow Clogged Tipping Bucket Gage
The Easiest Design Is Not Always The Best
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Tipping Bucket Mechanism Does Not Measure Snow
Events, And Frequently Under-Reports Intense
Rainfall
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Snow Sticking to The Un-Heated Chute of a
Weighing Precipitation Gage
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Same Gage Type Clear of Snow When Equipped With a
Heater
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Chute Temperature Rises When Heater is Activated
Air Temperature
Wetness Sensor Readings
Traces of Three Precipitation Sensors
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Wetness Sensor Activation Confirms Period Of
Precipitation
Three Independent Sensors Of The Gage Measures
Intense Precipitation Accurately