1. The Surprising Impact Stuff on the Tower has on Meteorological Data NUMUG Meeting Chicago June 2011 Jim Holian, SAIC

2. NUMUG SAIC Tower, Conduit, and Equipment Impacts on Wind Speed and Direction

3. NUMUG SAIC

7. Wind-Speed Averages (Unobstructed) ImpactHoursA Avg.B Avg.Diff. 100-M WS 743313.912.81.4 60-M WS 763711.810.31.5 10-M WS 77547.87.00.9 NUMUG SAIC

8. Wind Directions from 195-245 degrees blow through tower Window is 25 degrees for vane and cup sensors and 30 degrees for sonic sensor NUMUG SAIC

9. Tower Interference MODYTMA100B100A60B60A10B10WD 4301213.013.412.913.010.710.6192 4301312.314.613.014.911.912.4209 4301416.610.816.411.814.59.7224 4301522.311.920.513.317.99.8238 4301619.49.517.910.815.37.8234 4301725.822.423.121.120.217.1261 4301816.513.214.211.612.18.8252 4301914.79.312.48.49.76.1235

10. Tower Interference - A Data Bad MODYTMA100B100A60B60A10B10WD 4301213.013.412.913.010.710.6192 4301312.314.613.014.911.912.4209 4301416.610.816.411.814.59.7224 4301522.311.920.513.317.99.8238 4301619.49.517.910.815.37.8234 4301725.822.423.121.120.217.1261 4301816.513.214.211.612.18.8252 4301914.79.312.48.49.76.1235

11. Tower Interference – B Data Bad MODYTMA100B100A60B60A10B10WD 4301213.013.412.913.010.710.6192 4301312.314.613.014.911.912.4209 4301416.610.816.411.814.59.7224 4301522.311.920.513.317.99.8238 4301619.49.517.910.815.37.8234 4301725.822.423.121.120.217.1261 4301816.513.214.211.612.18.8252 4301914.79.312.48.49.76.1235

12. 10-m Wind-Speed Averages Tower Impact ImpactHoursA Avg.B Avg.Diff. 10-M WS-A 3947.78.1-0.4 10-M WS-B 2257.14.32.8

13. 60-m Wind-Speed Averages Tower Impact ImpactHoursA Avg.B Avg.Diff. 60-M WS-A 3649.810.3-0.5 60-M WS-B 28510.56.63.9 NUMUG SAIC

14. 100-m Wind-Speed Averages Tower Impact ImpactHoursA Avg.B Avg.Diff. 100-M WS-A 40910.012.7-2.7 100-M WS-B 26613.47.36.1 NUMUG SAIC

15. Wind-Direction Averages (Unobstructed) ImpactHoursA Avg.B Avg.Diff. 100-M WD 73751841822.6 60-M WD 39701841803.6 10-M WD 61481951896.7 NUMUG SAIC

16. 10-m Wind-Direction Averages Tower Impact ImpactHoursA Avg.B Avg.Diff. 10-M WD-A 4022031976 10-M WD-B 802432367 NUMUG SAIC

17. 100-m Wind-Direction Averages Tower Impact ImpactHoursA Avg.B Avg.Diff. 100-M WD-A 4512031994 100-M WD-B 1452402355 NUMUG SAIC

18. Electric Boxes at Sensor height NUMUG SAIC

20. Pole Interference with Wind Speed NUMUG SAIC

21. Pole NUMUG SAIC

22. Antenna and Associated Conduit Interference with Wind Speed NUMUG SAIC

29. YearTotal Hours Freq. (%) A System (mph) B System (mph) Diff. (mph) 2009164519.816.416.50.1 2007178921.915.815.90.1 Average Wind Speed from Totally Unobstructed Directions (180°-230°) NUMUG SAIC

31. YearTotal Hours Freq. (%) A System (mph) B System (mph) Diff. (mph) 20091752.110.612.82.2 20071031.311.913.01.1 Average Wind Speed Blowing Through Conduit to System A Sensor (355°-010°) with System B Sensor Unobstructed NUMUG SAIC

33. YearTotal Hours Freq. (%) A System (mph) B System (mph) Diff. (mph) 20091451.812.313.71.4 20071171.413.113.40.3 Average Wind Speed Blowing Through West Antenna to System A Sensor (345°-355°) with System B Sensor Unobstructed NUMUG SAIC

35. YearTotal Hours Freq. (%) A System (mph) B System (mph) Diff. (mph) 20092933.510.411.10.7 20071992.411.312.71.4 Average Wind Speed Blowing Through West Antenna and Conduit to System B Sensor (010°- 025°) with System A Sensor Obstructed by Tower NUMUG SAIC

37. YearTotal Hours Freq. (%) A System (mph) B System (mph) Diff. (mph) 20096668.011.59.9-1.6 20074956.113.411.5-1.9 Average Wind Speed Blowing Through South Antenna to System A Sensor (040°-060°) with System B Sensor Obstructed by Tower NUMUG SAIC

39. YearTotal Hours Freq. (%) A System (mph) B System (mph) Diff. (mph) 200992011.114.113.5-0.6 20076548.013.913.7-0.2 Average Wind Speed Blowing Through South Antenna to System B Sensor (065°-085°) with System A Sensor Unobstructed NUMUG SAIC

40. Tower Interference with No Additional Equipment and Limited Conduit Dedicated Met Tower Concept NUMUG SAIC

44. Wind-Speed Averages – A System in Tower Wake ImpactHoursA Avg.B Avg.Diff. 10-M WS 1624.64.50.1 60-M WS 974.14.7-0.6 100-M WS 455.26.5-1.3 NUMUG SAIC

45. Wind-Speed Averages – B System in Tower Wake ImpactHoursA Avg.B Avg.Diff. 10-M WS 1066.86.90.1 60-M WS 2926.46.1-0.3 100-M WS 1897.27.1-0.1 NUMUG SAIC

46. What Caused 100-Meter Impact of 1.3 MPH? Close Review of data indicated almost 3 mph difference with wind directions from 339-347 degrees.. This accounted for nearly all of the difference at the 100-meter level. Large Beacon Light is on north tower leg at top of tower. NUMUG SAIC

47. Conclusions Tower wake, equipment, and conduit have no measurable impact on wind direction. Greatest impact is on wind speed. Differences up to 10 mph seen at wind speeds above 20 mph. Obstructions such as antennas, beacons, and associated conduit have measurable impacts. NUMUG SAIC

48. Conclusions (cont’d) Dedicated meteorological towers have significantly less equipment and conduit and therefore have less interference. Having dual systems on separate faces of the tower appears to minimize wake effects due to spreading out of conduit, bracing, etc The data suggests that the sonic sensors may be influenced less by tower wake – not convinced. NUMUG SAIC