300m south sonic
Not sure when this happened, but suspect during either the Jun 4th or 5th lightening storms.

Sonic still working after being hit. No signs of damage to north sonic

250m south boom
For some reason the south boom at 250m is shorter than all the rest. Neither Bruce nor I can remember why this is or when it happened. 250m except for LUMEX and XPIA has not been instrumented.

Measurement from the center of the sonic path to the south leg is 3.15m

Sonics and T/RH at 300, 250, 200, and 150m have all been removed.

BAO Ceilometer and Sodar data files
Here is where you can find the raw data files for both the mono-static sodar and ceilometer located at the visitor compound:

ftp://ftp1.esrl.noaa.gov/psd3/bao/Ceilo/raw/    (Vaisala binary)

This file describes the data format:
ftp://ftp1.esrl.noaa.gov/psd3/bao/Ceilo/readme_ceilometer_BAO.txt

ftp://ftp1.esrl.noaa.gov/psd3/bao/Tower/Sodar/Raw/     (netcdf)

This file describes the data format:
ftp://ftp1.esrl.noaa.gov/psd3/bao/SODAR/Sodar_Readme.txt

We use MATLAB to read the raw files. We can get you the code if you want.

Profiling lidar

For the profiling lidars, we plan:

- global study (throughout XPIA) comparing the WCv1 lidars to each other and to the WCv2 lidar (after it was deployed 12 March)
- global study (throughout XPIA) comparing the lidars to tower sonics for mean wind speed and direction
- global study (throughout XPIA) comparing the wind fluctuations from the lidars to TKE from the tower sonics
- case study of some interesting LLJs (0-6 UTC) such as 5 March, 16-17 March (odd NEly jet), 4 Apr, 6 Apr (2-6 UTC), 6-7 Apr (22-4 UTC), 10 Apr (0-6 UTC), 12 Apr (0-12 UTC), 14 Apr (0-8 UTC, very strong),  23 Apr (0-8 UTC, very strong, sswly), 24 Apr (0-6 UTC, pulsing LLJ, NWly)

 

UTD preliminary data analysis

The UTD team proposes to work on the evaluation of the scanning lidar accuracy for different configurations and atmospheric conditions. This analysis is carried out by comparing the 200S radial velocity with the sonic data acquired by the met-tower and the profiling lidars. The sonic and profiling lidar data are projected over the 200S line-of-sight in order to produce an equivalent radial velocity.

For this analysis an "effective" range gate is evaluated, i.e. the projection of the range gate over the horizontal plane and mean wind direction. This parameter is considered to be the sensitive measurement volume of the lidar. The vertical extent of the lidar range gate is also evaluated, which is a parameter to estimate the effect of wind shear on the radial velocity.

The error analysis will be performed by considering different stability regimes, turbulence intensity, wind shear and veer.

After this error analysis for the radial velocity of single lidars, the retrieval of 3D velocity components from 3 intersecting and synchronous lidars will be carried out. For this analysis a crucial point is the definition of the effective measurement volume determined by the intersection of the 3 range gates.

For the proposed analysis the following experiments will be investigated:

• Dual/Triple Doppler Stares - Sonic + Lidar Supersite 3/21/2015-3/24/2015
• Dual/Triple Doppler Stares - Sonic + Lidar Supersite + Radar Site 3/24/2015-4/1/2015

Tower power issue solved (we hope). Thanks to some excellent weather and Bruce's sleuthing we feel we have the breaker issue solved. There was a worn wire inside one of the electrical boxes at ~125m that was shorting out. Tower vibrations and temperature swings over 40 years. It's amazing there aren't more problems"  (knock on galvanized steel").

BAO Tower Update 2015-05-27
200 and 300m T/RH not working. Starting Sat May 23 1900 UTC
Probably will not be replaced.
Lost NCAR and some standard BAO tower data over weekend. Back up  Tuse May 26.

Tower data outage

The breaker that provides power for the tower instruments and the network link to Boulder tripped some time about 2015-05-25 00:12z.
Bruce has reset the breaker and things seem to be coming back to life.
The outage lasted about 42 hours.

(From email from Bruce Bartram) 

Weibull distributions from the tower

As part of Paul's explorations of the differences between the NW and SE sonics and the profiling lidars, he has prepared wind speed distributions for the 50m, 100m, and 150m levels. All levels fit the Weibull distribution very well. The Weibull parameters are summarized in a table below.

The differences between the NW and SE booms are very subtle.

Tower wakes and accelerations

We can easily understand that a meteorological tower will affect the measurements taken within the wake of the tower. Here at the BAO, we are suspicious of measurements on the SE boom when the winds are from the NW, and similarly, we look for wakes in the NW boom data when the winds are from the SE. However, we should also remember that flow around a tower like the BAO can also generate accelerations for certain wind directions as well around the tower as well. The IEC standard 61400-12-1 Annex G specifies boom lengths (as a function of tower dimension and tower solidity) to ensure that measurements are taken outside of the zones of these wakes and accelerations.

CFD simulations (caveat: neutral stability) for flows around towers like the BAO can illustrate these issues. An example is shown below, from Stickland et al. 2012 (EWEA), for simulations of flow around the FINO3 tower (*not* the BAO).

As flow approaches from the left, the flow decelerates in an induction zone (cool colors are flow less than 100% inflow speed), but also accelerates (warm colors) around the sides of the tower.

As a reminder, here is what our tower looks like. Last week, I checked with Dan Wolfe regarding the tower solidity (as the degree of acceleration and deceleration depends on tower solidity), and such measurements have not yet been done for the BAO.

 
But what do our data show? Rob has pointed out below that the ratios of the sonics on the two booms show some evidence of both wakes and accelerations. Paul Quelet at CU has also looked at this issue, comparing the sonics to each other and to the profiling windcube (WC) lidars at the lidar supersite 135 m south of the tower. Because of the lidar comparison, Paul looks at 2-min averages of the tower sonic data at 50 m, 100 m, and 150 m:

It's interesting that the NW boom, on average, is always faster than the SE boom data, even when the NW boom should be waked. When the SE boom is waked (wind directions ~ 330), the differences are large as would be expected.

Then, when comparing the tower sonics to the lidars south of the tower, some other interesting differences emerge. Let's look at the NW boom data first:

We're comparing the WC to the NW boom sonic wind speeds. When the flow is from the south-east, the NW boom is clearly in the wake and the lidar speeds are much higher. Conversely, when the winds are from the NW, the WC measures low...but at 130 m away to the south, the WC should not be sampling tower wake. So when we see the WC measuring "low" at wind directions ~ 320, are we actually seeing the sonics measuring accelerations around the tower? Or is the tower wake propagating further downwind than we would expect?

The picture from the SE boom is different. First, the data are noisier, with lower wind speeds generally introducing more variability into these 2-min averages.
  

Second, the really puzzling thing is that the WC is still seeing higher winds than the sonic when the winds are from the south-east. The sonic isn't waked from this direction - why would the sonic wind speeds be low (or the WC winds be high)? Further, the wake effect we would expect to see when the winds are from the northwest isn't distinct.

Paul is continuing to work on this analysis, using higher time resolution data and stratifying these effects by atmospheric stability.

A major caveat to this quick analysis is that the sonic data, as yet, have not been corrected for any tilt in the booms. A systematic tilt issue could modify these results significantly. 

Thanks, Paul, for all your work on this so far!


 

As I recall, Julie had previously pointed out a few instances of tower wake effects as seen in the differences between the SE and NW sonic pairs. As I started digging into the sonic data it became apparent that there were many cases where there were huge differences in wind speeds between the SE and NW sonics.
The plot above shows the mean relative difference between the SE and NW sonic wind speeds as a function of the SE sonic wind direction at the 250 m level. The other levels look similar. The plot was obtained by averaging 1-sec sonic data from March 6 through May 16. In this case the max occurs when the NW sonic is in the tower wake, and the minimum occurs when the SE sonic is in the tower wake. As you can see the differences can be huge.
What I find really interesting is the fact that the difference changes sign as you move away from the wake zones. One interpretation might be that the wind speed is slightly higher than the free stream in a region just outside of the wake zone. Is that possible? Has such a thing been observed or modeled?

Platform operations

Click here for summary of motion platform operations. Updated daily.

Nighttime motion platform operations at BAO Area 51.

BAO Tower instrumentation 2015-05-14
Due to a tripped breaker some of the tower sonic and T/RH data maybe be missing.
~ Times are 1537-1730 UTC

Link to tower data viewer has changed

As we discussed in the call Wednesday morning, the NCAR data browser seemed to be down. It has just moved to http://datavis.eol.ucar.edu/ncharts/projects/CABL/qc_geo_notiltcor. I've corrected the link at right.

BAO 28 Apr 2015
~1730-1800 UTC the T/RH was replaced at 300m. S boom was in (bad directions) and N boom may be off by 5- 15 degrees too.
NCAR reported all looks good now.
~,4" of precip with last system.

Data and quicklooks from the Halo Photonics Streamline lidar are available at


https://engineering.arm.gov/~newsom/Doppler/offsite/xpia/Halo/


This includes the "raw" radial velocity data, as well as processed VAD winds, and vertical velocity statistics (variance, skewness, kurtosis, cloud base height, cloud fraction, cloud base vertical velocity, and velocity precision estimates).


The Halo maintained a consistent scan schedule throughout its deployment period (from March 6th to April 16th). The scan schedule was as follows:

• 8 beam PPI scan at 60 deg elevation once every 12 minutes.
• narrow sector scan toward light posts near the EHS stadium once per day.
• ~10 minute slant-path stare near 50-m level on the BAO tower once per hour.
• Vertical stares the rest of the time.

The Halo was operated using a 30-m gate size, and with a 1-second pulse integrate time. The maximum number of gates was set to 200. With the exception of a fairly minor software glitch on the April 9, the Halo functioned quite well. The glitch resulted in downtime during the latter half of April 9th, all of the 10th, and the first half of April 11th.

Motion Table April 24, 2015
Looks very cool, especially when moving.
What you see is the motion table mounted on the trailer with the Vindicator "Egg" sitting on the platform. The trailer sits inside a wind screen/break.

The air compressor that provides power to the motion arms is covered by the blue tarp off to the left.

BAO 300m T/RH
Now the fan on this sensor has gone bad.  We measure the fan current and our software removes data when the fan is not operating.  We could use the data, but they would be contaminated by a radiative heating error.

Replacement being prepared by NCAR and will be replaced some time next week.

All other sensors working.

3D Volume Scans

Over the last three days, the four 200S lidars and HRDL were engaged in testing various configurations of volume scans to measure and visualize flow behind a wind turbine.  With this goal, the following two configurations were tested.

1. Small box pattern:

This pattern has a high update rate of once every 15 sec.  It envelops a small volume of 100mX100m and from 30m above ground to 130m above ground.  This pattern is focused on producing retrievals just behind or ahead of a wind turbine.

2. Medium box pattern:

This pattern covers a slightly larger volume of approx 400mX400m and from surface to 200m above the ground with ~15m vertical resolution at each of the scan intersections.  Due to the larger area coverage the update rate is reduced to once every 1 min.

Sonde Schedule

Weather warning - hard hats recommended near the guy wires due to chance for falling ice

Posting for Dan Wolfe:

The situation at the BAO is extremely wet, slushy, and messy. Over 1.5" of precip have fallen, which is a lot of this site, so even the roads are likely to be complicated. There could be slush or possible ice on the tower and guys, so activity near the guys should include using hard hats (available in the Visitor Center and in the trailer at the tower base) in case of ice falling from the guy wires.

UTD 200S: Assessment of LiDAR measurements against sonic anemometry

The UTD team is working on the intercomparison between the radial velocity measured by the UTD WindCube 200S and the 3D velocity measurements carried out with the CSAT3 sonic anemometers installed over the met-tower. In this post measurements performed in proximity of the sonic anemometer installed on the South-East boom at height of 50 m are shown. For this test the UTD 200S measured with an elevation angle of 11.49 deg, and the azimuthal angle between the laser beam and the SE boom was 98 deg. The three wind velocity components measured by the CSAT3 are retrieved in order to obtain the equivalent radial velocity seen by the UTD 200S. In Fig. 1 the comparison between the radial velocity retrieved from the sonic data and the one measured by the UTD 200S clearly shows a very good agreement between the two measurement techniques. These data were acquired from 2015-03-22 16:00:08.806244 UTC till 2015-03-22 16:14:38.285902 UTC. For this analysis no temporal correction was performed, assessing the time synchronization of the LiDAR carried out with the embedded GPS. 

Fig. 1: Comparison between the 3D velocity data obtained from the CSAT3 sonic anemometer and the radial velocity measured by the UTD 200S.

  In the following some numbers to quantify the LiDAR accuracy:

Mean value for the lidar radial velocity: -3.07 m/s

Mean value for the sonic radial velocity : -2.91 m/s

Standard deviation for the lidar radial velocity: 0.32 m/s

Standard deviation for the sonic radial velocity: 0.42 m/s 

The higher standard deviation of the sonic data is connected to the higher sampling rate (20 Hz for the sonic and 2 Hz for the LiDAR) and smaller sampling volume (30 cm for the sonic, 50 m for the LiDAR).

In Fig. 2 a zoom in of the comparison between the sonic and LiDAR data is reported.

Fig. 2: Comparison between the radial velocity measured by the UTD 200S and the one retrieved by the sonic anemometer CSAT3 installed on the SE boom at 50 m height.

Finally, accuracy of the LiDAR measurements can be better appreciated when LiDAR data are compared with the wind shear measured by the sonic anemometers deployed at different heights.

Fig. 3: Intercomparison between the UTD 200S measurements performed in proximity of the sonic anemometer at 50 m height and the wind data acquired by the sonic anemometers deployed at different heights.

The regression analysis of the LiDAR data vs the sonic anemometer data shows a slope of  1.072 and an R-squared value of 0.6682 (Fig. 4).

Fig. 4: Linear regression between LiDAR data and sonic anemometer data.

Motion Table
For those of you who can't make it out to the site, here are a couple of pictures of the motion table.

Temperature Profiles at Watertank

Last Friday a Kipp & Zonen Microwave Temperature Profiler (MTP-5) was installed at the LeftHand Water District site (a.k.a. Watertank). Below the timeseries for Saturday and Sunday (top and bottom images, respectively). This instrument is generating a temperature profile every 5 minutes with a vertical resolution of 50 m from the surface up to 1 km. 

Figure 1. Microwave temperature profiler timeseries for April 11 (top) and 12 (bottom), 2014.

Updated tower files

A very small error in boom orientation (3 degrees) has been identified, and Gordon Maclean from NCAR has corrected the datafiles as of 13 Apr. Gordon says:

The netcdf files have been reprocessed with updated boom azimuths of 154 and 334.

This includes the 5 minute files at ftp://ftp.eol.ucar.edu/pub/archive/isff/projects/cabl/netcdf_qc_geo_notiltcor

and the high rate files at ftp://ftp.eol.ucar.edu/pub/archive/isff/projects/cabl/netcdf_hr_qc_geo_notiltcor

The high rate files have also been re-formatted. They now contain 12 hours of data instead of 4, and so for each day the files are named cabl_ntc_YYYYMMDD_HH.nc, where HH is 00 and 12.   If you've downloaded high-rate files before, you should replace the 00 and 12 files with the new ones and delete files with HH fields of  04,08,16 and 20.

BAO 2015-04-13
All tower sensors working. Strong winds over weekend...all booms secure.

NOAA radiometer pressure way off and not tracking.

UTD 200s: RHIs and Virtual tower experiment

The UTD 200S and the two NOAA 200S have been performing simultaneous Range-height indicator (RHI) scans, which are performed by keeping fixed the azimuthal angle of the scanning head and sweeping the elevation angle within a certain range. The three LiDARs performed scans by intersecting the three measurements plans in correspondence of the lidar supersite location, in proximity of the SE sonic anemometers of the met-tower, and over another location where the TTU ka-band radar was also performing virtual tower measurements. Preliminary data analysis shows the characterization of wind shear and low level jet through the RHI measurements.

  Fig. 1: RHI scans during the occurrence of a Low-Level Jet.

Fig. 2: Wind shear characterized through RHI scans.

Fig. 3: Wind shear characterized through RHI scans.

Rotated radimeters for low-level scans @ 0deg elevation angle

The radiometers were rotated by 90 degrees on Tuesday (7 April) scanning now east-west instead of north south. This allows for low-level scans at 0deg elevation angle. Attached is a figure showing the new configuration looking towards SW.