The wind direction part of the anemometers still seems to not be reading correctly. There was some discussion on the SEI call today that maybe it had started working, but a look at the DetChar page at https://ldas-jobs.ligo-wa.caltech.edu/~detchar/summary/day/20160714/pem/wind/ shows good info for wind speed, but nothing sensible for wind direction. I put some data into the SEI log about wind direction as seen at the Tri-cities airport. https://alog.ligo-la.caltech.edu/SEI/index.php?callRep=1035 The FAA and Jim agree that strong winds come from the southwest.
Speaking as an ex hang glider I don't think we will get reliable wind measurements unless the sensors are placed well above the buildings. Here is a quote from the World Meteorlogical Organization;
https://www.wmo.int/pages/prog/www/IMOP/publications/CIMO-Guide/Prelim-2014Ed/Prelim2014Ed_P-I_Ch-5.pdf
John W. is right that the wind direction at our roof weather stations is not what it would be on a weather mast far above land topography. The wind affecting the buildings is funneled by the buildings themselves as well as by the berms and other topography around them. Since we care more about the direction of the wind that is flowing over and around the buildings, than we do about the direction at altitude, I have not pushed to build weather masts as was done at LLO, but, of course, this means that the sensors do not read what masts read. Mast wind directions are available from Hanford weather services (http://www.hanford.gov/page.cfm/HMS/RealTimeMetData), station 9 is closest to the corner station and station 1 is closest to EY. But I think you have to contact them to get historical data.
To reflect that our roof weather station direction sensors are very local sensors and do not report what meteorologists think of as wind direction, for aLIGO we started using our own X, Y coordinates:
Wind travelling in +X direction (from corner station towards X end): 0 (degrees)
Wind travelling in the +Y direction (from the corner station toward EY): 270
Wind travelling in the -Y direction, EY to CS (approx. direction of typical storm): 90
Wind travelling in the -X direction, EX to CS (the other most common storm direction): 180
That being said, the wind direction system has not yet been installed. This is because all sensors were broken by the beginning of aLIGO, long past their life span. Paul Schale and I installed a new direction sensor at EX in summer of 2014 for BRS studies. I looked back at the data, and for some reason it starts in April of 2015, but from then on the data is good. The channel is: H1:PEM-EX_WIND_WEATHER_DEG. I just now went up on the roof and made sure that it was still functioning with directions as given above. However, even this new sensor has problems typical of the Davis system: it sometimes produces huge values, I believe when the brushes loose contact around 0 degrees.
Let me say that for most studies, I am inclined to use proxies that are closer to what we care about than wind direction at one particular location on the roof. Thus for studies of how the BRS performs under different wind tilt conditions, such as dominant tilt direction, I suggest using the 0.03 to 0.08 Hz seismic band of uncorrected seismometers. This gives both tilt axes so that the performance can be compared when most of the tilt is in the Y direction or in the X direction (we only have real tilt sensors (BRS) at EX and EY for the beam axis direction, hence the need for a proxy). Of course earthquake spikes must be filtered out. This is how Dipongkar did his year long study of tilt behavior (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=17574, https://wiki.ligo.org/viewauth/DetChar/WindInducedTilt). Included in this study are plots showing how well this seismometer band correlates with the tilt as measured by the BRS.
For the person installing the new anemometer/wind direction sensors (Hugh is considering taking this big job on), in order to get the direction system above, align the bar in the Y-direction with the anemometer towards Rattlesnake mountain. Use a CDS laptop displaying the weather screens for fine adjustment.
Robert