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margarita.vidrio@LIGO.ORG - posted 15:24, Friday 25 July 2014 - last comment - 14:27, Friday 01 August 2014(12996)
Statistics for 8 years of wind at LHO

Summary: Eight years of wind data at 3 LHO stations were analyzed. Fifteen percent of hours had wind speeds exceeding 10 m/s, the speed at which displacement and tilt from wind start to significantly increase the seismometer signals. Nearly 25% of hours in April, the month with the highest average wind speed, have winds exceeding 10 m/s. Data are also shown for individual stations; readings for EY are the highest.

Introduction: The analysis of wind data is important because wind speeds over 10 m/s increase ground motion and thus affect interferometer performance. This increase in ground motion is caused by wind interacting with the topology of the site and, most importantly, the surfaces of buildings. In addition to producing displacements, wind blowing on the buildings can tilt them, which can produce spurious acceleration signals from seismometers.

Methods: Eight years of data between 2004 and 2012 were analyzed for patterns across the years. The data was extracted from DataViewer for the Corner Station (CS), End Station X (EX), and End Station Y (EY). The "Maximum Channel" was selected of the "Hourly Trend" setting within DataViewer. This time period was selected because it was not missing more than 58 days of data at a single time in the series and only a total of 218.7 days were missing from the entire data source. This amounted to about 8% of the data missing from the entire data set. The data was considered missing if DataViewer did not provide it.

Results: The first figure shows that 15% of the hours in the 8 years analyzed exceeded 10 m/s, which significantly increases ground motion. The second figure shows that, during each of the spring months, the wind was greater than 10 m/s in more than 15% of the hours, peaking at 24% in April. The third figure shows that the average hourly maximum wind speed varied the most from year-to-year in the month of February. The fourth figure includes statistics for the individual stations. Averages for EY are higher than for other stations. For example, 27% of April hours exceed 10 m/s at EY while the average for all stations was 24%.

Margarita Vidrio, Robert Schofield

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margarita.vidrio@LIGO.ORG - 14:27, Friday 01 August 2014 (13154)

In Fig 5, the wind speeds exceed 10 m/s thirty eight percent of the time in June at 2 AM and April at 11 PM. Also, the month of December shows a consistent percentage (between 8%-10%) of wind speeds over 10 m/s across all times of the day.

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