Dec.  31, 2001

Information file for the National Oceanic and Atmospheric Administration/Environmental
Technology Laboratory's TEACO2 Doppler Lidar wind profiles                 

TexAQS 2000

Text files are found at www.etl.noaa.gov/~ldarby/houston_profiles/text_files.
PostScript files containing wind barb profile plots are found at 
www.etl.noaa.gov/~ldarby/houston_profiles/graphics_files.  At this time, this directory contains
profiles from 1 to 2 constant-elevation scans for each day.  Profiles from 20 to 30 scans are
available for some days.

*** Important note: Data in the text files are in UTC.  Times were converted to LST (UTC - 6)
for the profile plots. ***

Please refer to Houston_vad_record for a listing of times of the first and last wind profiles
available for each day.  

1. File name conventions:
File name convention for text files
MMMDD.txt

MMM is the month
DD is the day

File name convention for graphics files:
MMMDD_N_Xdeg.txt

MMM is the month
DD is the day
N is the minimum elevation angle of the scans the profiles were derived from.
X is the maximum elevation angle of the scans the profiles were derived from.

Some files have 'all' in the name, which signifies that all profiles from that day were plotted.
Some files have 'sub' in the name, which signifies that a subset of profiles were plotted.
Otherwise, all times appear in the plot.

2.  Site information:
The TEACO2 Doppler lidar was stationed at the general aviation airport in LaPorte, TX.
LAT 29.66917, LON -95.06417, 7.3 m ASL

3. Data:
Each profile has 2 header lines

1st header line:

1.  File number on original data tape
2.  Month
3.  Day
4.  Year (year 100 is year 2000)
5., 6., and 7. Hour, minute, and second (in UTC), respectively, of the start time of the file.  If
there is more than one profile in a file, all will carry the same start time as the start time of the
file.  Each plan-position indicator (PPI) scan (from which the profiles are derived) takes
approximately 1 minute and 48 seconds to obtain.
8.  Fixed elevation angle, in degrees.  For example, if 1.000 is the fixed angle, the scanner
remained at 1 above the horizon while sweeping in azimuth.
9., 10., 11.  Internal housekeeping fields - please disregard

2nd header line:

1.  ALT is the height above ground in kilometers (relative to the lidar)
2.  WIND SPD is wind speed in m/s
3.  WIND DIR is wind direction in degrees from north
4.  SNR is signal-to-noise ratio
5.  % GOOD PTS is the percentage of good points in the profile
6.  WV
7.  RMS ERROR is the root mean square error in m/s

The last 4 columns may be used to threshold the data.   
Values used to threshold the data plotted in the files found in the graphics_files directory:
minimum percentage good points = 17
minimum snr = -35
max wv = 10
max rms error = 1.5

Each individual researcher is free to determine the most convenient way to threshold the data for
their purposes.

4.  Known problems with the data:

From 8/20/00  to 8/22/00 there was a problem with the scanner that resulted in the elevation
angle of the scanner gradually increasing with time.  Once the problem was discovered, the
scanner was re-aligned approximately every hour to minimize the drift, until the problem was
resolved with a replaced part.  Known maximum elevation angle errors for these days are: 4.12
at 2140 UTC on Aug. 20, 4.49 at 1950 UTC on Aug. 21, and 1.43 at 1459 UTC on Aug. 22. 
This elevation angle drift results in errors in the calculated height above ground level (the ALT
column) for these days.  These errors have not been corrected.

At 2312 UTC on Aug. 31st, the scanner elevation angle was 5 too high.

5.  Data use policy:

We request that a proper acknowledgment to the "NOAA Environmental Technology
Laboratory" accompany the use of this data in any publications and presentations.  If the use of
the data in a publication constitutes a major or reasonably significant aspect of an article,
co-authorship by an ETL scientist is appropriate; please discuss any such planned use with the
scientist listed below. We  welcome collaborations and will lend our scientific expertise in
interpretation and evaluation of the data. 

Lisa Darby, lisa.darby@noaa.gov