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Upper portion of hotplate

The Hotplate Snowgauge Roy Rasmussen, NCAR John Hallett and Rick Purcell, Desert Research Institute Jeff Cole, Matt Tryhane, and Scott Landolt, NCAR Supported by FAA AWRP Program.

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Upper portion of hotplate

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  1. The Hotplate SnowgaugeRoy Rasmussen, NCARJohn Hallett and Rick Purcell, Desert Research InstituteJeff Cole, Matt Tryhane, and Scott Landolt, NCARSupported by FAA AWRP Program

  2. Motivation1. Need to measure real-time liquid equivalent snowfall rates to determine holdover times for aircraft ground deicing purposes.2. Most weighing snowgauges do not measure snowfall rate in real-time: - Sidewall accumulation3. Most weighing snowgauges require the use of Glycol and oil, which needs to be changed regularly. 4. Weighing snowgauges also require the use of wind shields to increase catch efficiency during windy conditions due to large size of the snow gauge.5. Moving parts such as vibrating wires tend to break. 6. Need to recycle the glycol. Roy Rasmussen, NCARJohn Hallett, Desert Research InstituteJeff Cole, Matt Tryhane, and Scott Landolt, NCARSupported by FAA and USWRP

  3. Upper portion of hotplate 13 cm

  4. 13 cm Lower hotplate

  5. Hotplate SnowgaugePrinciple of operation: Separately heated aluminum plates with an insulator in between. Both plates heated to 75 C, and maintained at that temperature electronically. Precipitation cools the top plate by melting and evaporation but not the bottom one. The power difference between the top and botton plates is proportional to the precipitation rate.

  6. ½ Wyoming shield Tretykov Wind shield NWS 8” precipitation can within single Alter wind shield

  7. Comparison of Original hotplate snowgauge with GEONOR gauge in DFIR (better than or equal to 8” NWS can with single Alter shield). Period: Jan. – April, 2001 and Jan. – March, 2002. Criteria for comparison: 1. The absolute value of the difference between the Geonor in the DFIR hourly accumulation and the Original Hotplate hourly accumulation shall be less than or equal to 0.02 inches, or 4% of the hourly total, whichever is greater. 2. The instrument also passed if there was no precipitation measurement during non-precip events (less than 0.001”/hr). Therefore, not giving any "false" accumulation reports. The above criteria is the ASOS program office criteria for evaluating weighing precipitation gauges.

  8. Comparison of Original hotplate snowgauge with GEONOR gauge in DFIR (better than or equal to 8” NWS can with single Alter shield). Results: Year 2001 2002 Total Storms Analyzed 7 13 Non- precipitation days analyzed: 4 77 Total # hours (storms): 137 174 Total # hours (Non-precip.) 90 1980 % hours passed (storms): 100% 99.43% % hours failed (storms): 0 % 0.57% % hours passed (non-precip.): 94% 97.98% %hours failed (non-precip): 6% 2.02%

  9. Comparison of Original hotplate snowgauge with GEONOR gauge in DFIR (better than or equal to 8” NWS can with single Alter shield).If assume threshold for no-precipitation is 0.005”/hr, then the hotplate would pass 100% for the non-precipitation cases: Results: Year 2001 2002 Total Storms Analyzed 7 13 Non- precipitation days analyzed: 4 70 Total # hours (storms): 137 174 Total # hours (Non-precip.) 90 1980 % hours passed (storms): 100% 99.43% % hours failed (storms): 0 % 0.57% % hours passed (non-precip.): 100% 100% %hours failed (non-precip): 0% 0%

  10. Summary 1. A hotplate snowgauge has been developed to measure the liquid equivalent snowfall rate every minute. Comparison of the hotplate performance during the past two years to a GEONOR snowgauge in the WMO standard windshield (DFIR) showed that the hotplate passes the NWS criteria for hourly precipitation measurement and false accumulations using a threshold of 0.005”/hr. • Current hotplate snowgauge works for snow rates up to 12 mm/hr. • Advantage of the hotplate over current weighing snowgauges are: • No moving parts (no vibrating wires to break) • No glycol or oil to change every few months. Also eliminates the environmental problem of glycol disposal. • Does not require a wind shield, saving both maintenance and initial cost. • Low maintenance. • Expected to be low cost.

  11. Summary (continued) 4. Working on a version of the hotplate that will work for rainfall as well as snow (hotplate precipitation gauge). 5. Actively seeking companies to commercialize the system. 6. The snow “hotplate” could be combined with the ASOS LEDWI to provide measurements of precipitation rate for rain and snow on the current ASOS systems (previous studies have shown that the LEDWI high channel is highly correlated with rainfall rate). We are currently working on developing an algorithm to do this.

  12. New Hotplate Precipitation gauge

  13. The End

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