Sodar - Vaisala Triton Wind Profiler, AON2 - Reviewed Data

**Overview**

This dataset contains measurements from eight different Vaisala Triton Wind Profiler instruments. The Triton Wind Profiler is a sodar wind profiler that measures wind speed, direction, and turbulence intensity at heights from 30 m to 200 m above ground every 10 minutes. The eight Tritons are located at various sites around the WFIP2 study area.

**Data Details**

Regarding the minimum requirements for the site description, a Keyhole Markup Language (KML) file is attached with all of the AON Triton locations. Unfortunately, there are no photos of the sites. The layout of each site is simple. At all locations, the Triton Wind Profiler is placed on the ground with the solar panel facing due south. Each unit is solar powered and communicates its data via satellite, so there are no cables of any kind. Also, the specified start and end dates are for the entire AON network. Some individual units start later or end earlier. All start/end dates for the individual units are given as follows:

AON1 (z17): 10/1/2015 -- 7/31/2017

AON2 (z14): 10/1/2015 -- 7/31/2017

AON3 (z18): 10/1/2015 -- 7/31/2017

AON4 (z12): 12/5/2015 -- 7/31/2017

AON5 (z06): 10/1/2015 -- 7/31/2017

AON6 (z05): 10/1/2015 -- 7/31/2017 (w/gap 2016-08-01 -- 2016-09-28)

AON7 (z02): 10/1/2015 -- 7/31/2017 (w gap 2016-07-01 -- 2016-11-18)

AON8 (z01): 12/7/2015 -- 4/9/2016

AON9 (z20): 11/19/2016 -- 7/31/2017

**Data Quality**

The Triton firmware has a quality assessment algorithm that assigns a quality factor (?quality?) to each time/height measurement of wind, expressed as a percent value in the range 0-100. In addition, the upward Doppler velocity (?vert?) is measured and can be used as an indicator of falling precipitation, which negatively affects data quality. Two automated procedures have been applied to this "ready-to-use" version of the data (level b0): data were set to a missing value (null in the CSV file) when either ?quality? < 90% or ?vert? < -1.5 m/s. Notably, turbulence has its own quality factor, which is used separately for filtering the turbulence variable (although vertical velocity filtering also is performed on the turbulence data). Finally, the data have been visually inspected for time periods that are obviously suspect, and those times have been set to missing. In general, the purpose of the b0 data level is to provide non-expert users with a dataset that they can be reasonably confident only contains good data, to the best of the instrument Principal Investigator's knowledge.

**Uncertainty**

When compared to nearby towers instrumented with cup anemometers and wind vanes, the root mean square (RMS) difference in 10-minute wind speed between the Triton and met tower typically is around 0.5 m s-1. When tested at 30 different sites in a recent validation study, the RMS difference in long-term mean wind speed between the Triton and met tower is 1.3%.

**Constraints**

Various meteorological and environmental conditions can lead to either weaker returns or enhanced noise, resulting in a poor measurement. The higher the target point, the more difficult it is to retrieve a strong signal. Hence, a common situation is that good data will be obtained up to some height then not above it. The percentage of time that good data are recovered at a particular height is the data recovery rate. In a recent validation study, data recovery rates were around 98% at lower heights, slowly dropping off to 96% at 100 m, 83% at 160 m, and 70% at 200 m.