The Surprising Impact Stuff on the Tower has on

Meteorological Data

NUMUG MeetingChicagoJune 2011

Jim Holian, SAIC

NUMUG SAIC

Tower, Conduit, and Equipment Impacts on

Wind Speed and Direction

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

Wind-Speed Averages (Unobstructed)

Impact Hours A Avg. B Avg. Diff.

100-M

WS7433 13.9 12.8 1.4

60-M

WS7637 11.8 10.3 1.5

10-M

WS7754 7.8 7.0 0.9

NUMUG SAIC

• 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

Tower Interference

MO DY TM A100 B100 A60 B60 A10 B10 WD

4 30 12 13.0 13.4 12.9 13.0 10.7 10.6 192

4 30 13 12.3 14.6 13.0 14.9 11.9 12.4 209

4 30 14 16.6 10.8 16.4 11.8 14.5 9.7 224

4 30 15 22.3 11.9 20.5 13.3 17.9 9.8 238

4 30 16 19.4 9.5 17.9 10.8 15.3 7.8 234

4 30 17 25.8 22.4 23.1 21.1 20.2 17.1 261

4 30 18 16.5 13.2 14.2 11.6 12.1 8.8 252

4 30 19 14.7 9.3 12.4 8.4 9.7 6.1 235

Tower Interference - A Data Bad

MO DY TM A100 B100 A60 B60 A10 B10 WD

4 30 12 13.0 13.4 12.9 13.0 10.7 10.6 192

4 30 13 12.3 14.6 13.0 14.9 11.9 12.4 209

4 30 14 16.6 10.8 16.4 11.8 14.5 9.7 224

4 30 15 22.3 11.9 20.5 13.3 17.9 9.8 238

4 30 16 19.4 9.5 17.9 10.8 15.3 7.8 234

4 30 17 25.8 22.4 23.1 21.1 20.2 17.1 261

4 30 18 16.5 13.2 14.2 11.6 12.1 8.8 252

4 30 19 14.7 9.3 12.4 8.4 9.7 6.1 235

Tower Interference – B Data Bad

MO DY TM A100 B100 A60 B60 A10 B10 WD

4 30 12 13.0 13.4 12.9 13.0 10.7 10.6 192

4 30 13 12.3 14.6 13.0 14.9 11.9 12.4 209

4 30 14 16.6 10.8 16.4 11.8 14.5 9.7 224

4 30 15 22.3 11.9 20.5 13.3 17.9 9.8 238

4 30 16 19.4 9.5 17.9 10.8 15.3 7.8 234

4 30 17 25.8 22.4 23.1 21.1 20.2 17.1 261

4 30 18 16.5 13.2 14.2 11.6 12.1 8.8 252

4 30 19 14.7 9.3 12.4 8.4 9.7 6.1 235

10-m Wind-Speed AveragesTower Impact

Impact Hours A Avg. B Avg. Diff.

10-M

WS-A

394 7.7 8.1 -0.4

10-M

WS-B

225 7.1 4.3 2.8

60-m Wind-Speed AveragesTower Impact

Impact Hours A Avg. B Avg. Diff.

60-M

WS-A

364 9.8 10.3 -0.5

60-M

WS-B

285 10.5 6.6 3.9

NUMUG SAIC

100-m Wind-Speed AveragesTower Impact

Impact Hours A Avg. B Avg. Diff.

100-M

WS-A

409 10.0 12.7 -2.7

100-M

WS-B

266 13.4 7.3 6.1

NUMUG SAIC

Wind-Direction Averages (Unobstructed)

Impact Hours A Avg. B Avg. Diff.

100-M

WD

7375 184 182 2.6

60-M

WD

3970 184 180 3.6

10-M

WD

6148 195 189 6.7

NUMUG SAIC

10-m Wind-Direction AveragesTower Impact

Impact Hours A Avg. B Avg. Diff.

10-M

WD-A

402 203 197 6

10-M

WD-B

80 243 236 7

NUMUG SAIC

100-m Wind-Direction AveragesTower Impact

Impact Hours A Avg. B Avg. Diff.

100-M

WD-A

451 203 199 4

100-M

WD-B

145 240 235 5

NUMUG SAIC

Electric Boxes atSensor height

NUMUG SAIC

NUMUG SAIC

Pole Interference with Wind Speed

NUMUG SAIC

Pole

NUMUG SAIC

Antenna and Associated Conduit Interference with

Wind Speed

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

Year Total Hours

Freq. (%)

A System (mph)

B System (mph)

Diff. (mph)

2009 1645 19.8 16.4 16.5 0.1

2007 1789 21.9 15.8 15.9 0.1

Average Wind Speed from Totally Unobstructed Directions (180°-230°)

NUMUG SAIC

NUMUG SAIC

Year Total Hours

Freq. (%)

A System (mph)

B System (mph)

Diff. (mph)

2009 175 2.1 10.6 12.8 2.2

2007 103 1.3 11.9 13.0 1.1

Average Wind Speed Blowing Through Conduit to System A Sensor (355°-010°) with System B Sensor

Unobstructed

NUMUG SAIC

NUMUG SAIC

Year Total Hours

Freq. (%)

A System (mph)

B System (mph)

Diff. (mph)

2009 145 1.8 12.3 13.7 1.4

2007 117 1.4 13.1 13.4 0.3

Average Wind Speed Blowing Through West Antenna to System A Sensor (345°-355°) with

System B Sensor Unobstructed

NUMUG SAIC

NUMUG SAIC

Year Total Hours

Freq.

(%)

A System (mph)

B System (mph)

Diff. (mph)

2009 293 3.5 10.4 11.1 0.7

2007 199 2.4 11.3 12.7 1.4

Average Wind Speed Blowing Through West Antenna and Conduit to System B Sensor (010°-

025°) with System A Sensor Obstructed by Tower

NUMUG SAIC

NUMUG SAIC

Year Total Hours

Freq. (%)

A System (mph)

B System (mph)

Diff. (mph)

2009 666 8.0 11.5 9.9 -1.6

2007 495 6.1 13.4 11.5 -1.9

Average Wind Speed Blowing Through South Antenna to System A Sensor (040°-060°) with

System B Sensor Obstructed by Tower

NUMUG SAIC

NUMUG SAIC

Year Total Hours

Freq. (%)

A System (mph)

B System (mph)

Diff. (mph)

2009 920 11.1 14.1 13.5 -0.6

2007 654 8.0 13.9 13.7 -0.2

Average Wind Speed Blowing Through South Antenna to System B Sensor (065°-085°) with

System A Sensor Unobstructed

NUMUG SAIC

Tower Interference with No Additional Equipment and

Limited Conduit

Dedicated Met Tower Concept

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

NUMUG SAIC

Wind-Speed Averages – A System in Tower Wake

Impact Hours A Avg. B Avg. Diff.

10-M

WS162 4.6 4.5 0.1

60-M

WS97 4.1 4.7 -0.6

100-M

WS45 5.2 6.5 -1.3

NUMUG SAIC

Wind-Speed Averages – B System in Tower Wake

Impact Hours A Avg. B Avg. Diff.

10-M

WS106 6.8 6.9 0.1

60-M

WS292 6.4 6.1 -0.3

100-M

WS189 7.2 7.1 -0.1

NUMUG SAIC

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

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

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