Evaluation of Winter Weather in Wyoming based on Numerical Weather Modeling for Snow Fence System Design

Transcription

1 Evaluation of Winter Weather in Wyoming based on Numerical Weather Modeling for Snow Fence System Design Noriaki Ohara University of Wyoming Low visibility due to blowing snow amplified the scale of the car crash on April 16, 2015, at 342 mile post on Interstate 80 [Photo: obtained from

2 Snow fence is known effective for the hazardous high wind and blowing snow conditions in Wyoming. Very little blowing snow behind fences at Mile 263.0, I-80 (Tabler 1973) From Tabler s book (Tabler, 2003) Photo by Robert L. Jairell

3 Snow fence design basics The wind and precipitation tables that are currently used were manually measured by Dr. Ron Tabler in the early 1990's.

4 Objectives To reconstruct the continuous long-term wind data in Wyoming for snow fence design using a numerical weather prediction model. To evaluate the evolving climate effect on the wind field last 30 years. Image:

5 Numerical Weather Prediction Model Application Model name: Weather Research & Forecasting (WRF) model Input: North American Regional Reanalysis (NARR) data The initial and boundary conditions of the WRF model were prepared from the NARR data. The NARR model assimilates a great amount of observational data to produce a long-term picture of weather over North America at 32 km resolution. Image:

6 Weather Research & Forecasting (WRF) model Computational grid sizes: 12 km

7 Reconstructed 10m wind field (movie) during the large event in Laramie Valley (June 1965) 2012 N.Ohara

8 SCRAM Surface Meteorological Archived Data ( ) WY24018 Cheyenne/Municipal Airport WY24021 Lander/Hunt Field WY24027 Rock Springs/FAA Airport WY24029 Sheridan/County Airport WY24089 Casper/Natrona Co Int'l Airport SCRAM = Support Center for Regulatory Atmospheric Modeling

9 WY24018 Cheyenne/Municipal Airport Simulated Observed 1/1/ /31/1992 WIND SPEED (m/s) >= Calms: 0.49% WIND SPEED (m/s) >= Calms: 1.28%

10 Model validation at WY24021 Lander/Hunt Field Simulated Observed 1/1/ /31/1992 WIND SPEED (m/s) WIND SPEED (m/s) >= Calms: 2.64% >= Calms: 19.19%

11 Simulated Model validation at WY24027 Rock Springs/FAA Airport Observed 1/1/ /31/1992 WIND SPEED (m/s) WIND SPEED (m/s) >= Calms: 0.82% >= Calms: 17.18%

12 Model validation at WY24029 Sheridan/County Airport Simulated Observed 1/1/ /31/1990 WIND SPEED (m/s) WIND SPEED (m/s) >= Calms: 4.65% >= Calms: 12.95%

13 Simulated Model validation at WY24089 Casper/Natrona Co Int'l Airport Observed /1/ /31/1992 WIND SPEED (m/s) >= Calms: 0.67% WIND SPEED (m/s) >= Calms: 0.99%

14 EAS EST WYOMING So, we can extract the continuous wind information at anywhere in Wyoming.

15 Modeled Wyoming-average wind speed Blue line = Wyoming-average wind speed (m/s) Yellow line = Moving average (n = 255) Black thick line = fitted linear trend line Wyoming has slightly gotten windier over the last three decades. rate = m/s per decade

16 Wind speed classification Force Speed Conditions Conditions Name knots km/h mi/h at Sea on Land 0 < 1 < 2 < 1 Calm Sea like a mirror. Smoke rises vertically Light air Ripples only. Smoke drifts and leaves rustle Light Small wavelets (0.2 m). Crests have Wind felt on face. breeze a glassy appearance Gentle Large wavelets (0.6 m), crests begin Flags extended, leaves move. breeze to break Moderate Small waves (1 m), some breeze whitecaps. Dust and small branches move Fresh Moderate waves (1.8 m), many breeze whitecaps. Small trees begin to sway Strong breeze Near gale Gale Strong gale Storm Violent storm Hurricane Large waves (3 m), probably some spray. Mounting sea (4 m) with foam blown in streaks downwind. Moderately high waves (5.5 m), crests break into spindrift. High waves (7 m), dense foam, visibility affected. Very high waves (9 m), heavy sea roll, visibility impaired. Surface generally white. Exceptionally high waves (11 m), visibility poor. 14 m waves, air filled with foam and spray, visibility bad. Definition: windy day = wind speed > 12mph (5.4 m/s) Large branches move, wires whistle, umbrellas are difficult to control. Whole trees in motion, inconvenience in walking. Difficult to walk against wind. Twigs and small branches blown off trees. Minor structural damage may occur (shingles blown off roofs). Trees uprooted, structural damage likely. Widespread damage to structures. Severe structural damage to buildings, wide spread devastation.

17 Frequency of windy days last three+ decades based on the reconstructed Wyoming-average wind speed for present Definition: windy day = wind speed > 12mph (5.4 m/s) Wyoming has more than 20 more windy days recently.

18 Modeled wind speed at Arlington Arlington, Wyoming Blue line = Wyoming-average wind speed (m/s) Yellow line = Moving average (n = 255) Black thick line = fitted linear trend line Arlington, WY, slightly has gotten windier over the last three+ decades. rate = m/s per decade

19 Frequency of windy days last three+ decades at Arlington, Wyoming Arlington, Wyoming Definition: windy day = wind speed > 12mph (5.4 m/s) Arlington has gotten about 20 more windy days recently.

20 Conclusions Numerical weather model can provide the historical longterm and seamless wind field data, which can be used for winter weather hazard protection planning. Wyoming has gotten windier over the last three+ decades. Next steps Combine the wind information with the snow condition. Analyze the blowing snow events using a finer resolution model. Acknowledgement This study is funded by Wyoming Department of Transportation. Noriaki Ohara, Ph.D. Assistant Professor Civil and Architectural Engineering University of Wyoming nohara1@uwyo.edu