Lidar - LMCT - WTX WindTracer, Gordon Ridge - Raw Data

**Overview**

Long-range scanning Doppler lidar located on Gordon Ridge. The WindTracer provides high-resolution, long-range lidar data for use in the WFIP2 program.

**Data Details**

The system is configured to take data in three different modes. All three modes take 15 minutes to complete and are started at 00, 15, 30, and 45 minutes after the hour.

*The first nine minutes of the period are spent performing two high-resolution, long-range Plan Position Indicator (PPI) scans at 0.0 and -1.0 degree elevation angles (tilts). These data have file names annotated with HiResPPI noted in the "optional fields" of the file name; for example: lidar.z09.00.20150801.150000.HiResPPI.prd.
*The next six minutes are spent performing higher altitude PPI scans and Range Height Indicator (RHI) scans. The PPI scans are completed at 6.0- and 30.0-degree elevations, and the RHI scans are completed from below the horizon (down into valleys, as able), up to 40 degrees elevation at 010-, 100-, 190-, and 280-degree azimuths. These files are annotated with PPI-RHI noted in the optional fields of the file name; for example: lidar.z09.00.20150801.150900.PPI-RHI.prd
*The last minute is spent measuring a high-altitude vertical wind profile. Generally, this dataset will include data from near ground level up to the top of the planetary boundary layer (PBL), and higher altitude data when high-level cirrus or other clouds are present. The Velocity Azimuth Display (VAD) is measured using six lines of sight at an elevation angle of 75 degrees at azimuth angles of 000, 060, 120, 180, 240, and 300 degrees from True North. The files are annotated with VAD in the optional fields of the file name; for example: lidar.z09.00.20150801.151400.VAD.prd.

LMCT does have a data format document that can be provided to users who need programming access to the data. This document is proprietary information but can be supplied to anyone after signing a non-disclosure agreement (NDA). To initiate the NDA process, please contact **Keith Barr** at keith.barr@lmco.com. The data are not proprietary, only the manual describing the data format.

**Data Quality**

Lockheed Martin Coherent Technologies (LMCT) has implemented and refined data quality analysis over the last 14 years, and this installation uses standard data-quality processing procedures. Generally, filtered data products can be accepted as fully data qualified. Secondary processing, such as wind vector analysis, should be used with some caution as the data-quality filters still are "young" and incorrect values can be encountered.

**Uncertainty**

Uncertainty in the radial wind measurements (the system's base measurement) varies slightly with range. For most measurements, accuracy of the filtered radial wind measurements have been shown to be within 0.5 m/s with accuracy better than 0.25 m/s not uncommon for ranges less than 10 km.

**Constraints**

Doppler lidar is dependent on aerosol loading in the atmosphere, and the signal can be significantly attenuated in precipitation and fog. These weather situations can reduce range performance significantly, and, in heavy rain or thick fog, range performance can be reduced to zero. Long-range performance depends on adequate aerosol loading to provide enough backscattered laser radiation so that a measurement can be made.