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EPIC Mini-MOPA Lidar data

Mini-MOPA Data Description


The Mini-MOPA Doppler lidar on the NOAA R/V Ronald H. Brown measured vertical profiles of wind velocity and direction during the period 12 September through 22 October, 2001. The lidar operated every day with some exceptions due to rain. The VAD technique (Browning and Wexler, 1968) was employed to process wind information taken in scanning mode (i.e. sweeping in a full circle around the compass (0 to 360 degrees) and then stepping up in discrete steps between 0 and 65 degrees in elevation angle) to produce high-resolution vertical profiles. A velocity profile is built from successive set of scans to produce the vertically resolved profiler-like data displayed in the images. Scans used to build the velocity profiles were taken no longer than 30 minutes apart. All velocities are in m/s and heights in meter.

Data format

Data file structure and file naming conventions: Two gif images are available, one representing the region from 0 to 1200 meters, and the other a closer view of the region from 0 to 200 meters. Also available are ASCII data files which include height, wind speed, direction and standard deviation. The naming convention for the data files is the following: dd-mm-yyyy [X]. Where d represents the day of the month, m represents the month of the year, and y is the year. If the file has a letter in square brackets, this corresponds in the following manner: [A] is the early part of the day, [B] is the later part of the day.

Data format and layout: The ASCII file header looks like the following:

36 0 29 4 9 7 2001 55.75 1.00 2
d:\EPIC\Data\010906\^numrows hr min sec mon dy yr el std_thr filenum/ v hght spd ang std

The second line describes the first line of the file as well as the data from the 3rd row and after.

First row:

  1. Data location, in the above example: d:\EPIC\Data\010906\ [string]
  2. numrows, the number of rows of data to follow the header, in the above example: 36 [integer]
  3. hr, the hour of the day corresponding to the profile, in the above example: 0 [integer]
  4. min, the minute of the hour corresponding to the profile, in the above example: 29 [integer]
  5. sec, the second of the minute corresponding to the profile, in the above example: 4 [integer]
  6. mon, the month of the year corresponding to the profile, in the above example: 9 [integer]
  7. dy, the day of the month corresponding to the profile, in the above example: 7 [integer]
  8. yr, the year corresponding to the profile, in the above example: 2001 [integer]
  9. el, the elevation angle corresponding to the elevation level of the scan of which the profiles were taken, in the above example: 55.75 This number is fairly arbitrary as multiple scans were used to calculate this high resolution profile. [float]
  10. std_thresh, the threshold in which the data standard deviation must not exceed to be included in the profile, in the above example: 1.0 [float]
  11. filenum, the original file number that the profile was calculated from, in the above example: 2 This number is arbitrary as multiple files were concatonated in order to calculate the velocity profile [integer]

Third and subsequent rows:

  1. v hght corresponds to the first column of data. These values are the vertical height in meters corresponding to the location of the measured velocity. [float]
  2. spd is the second column of data. These values are the wind velocity in meters/second.
  3. ang corresponds to the third column of data. These values range from 0 to 359 degrees. Where a value of 90 represents easterly flow, and 0 (or 360) represents northerly winds.

List of parameters with units, sampling intervals, frequency, range: The parameters represented in this file are height [meters], velocity [meters/sec], wind direction [degrees], and standard deviation. The values were calculated by averaging scans (in the elevation plane) in which the time between them is no longer than 30 minutes.

Description of flags, codes used in the data, and definitions (i.e., good, questionable, missing, estimated, etc.): The missing or bad data flag in this data set is -999.0

Reference:

Browning, K.A., and R. Wexler, The determination of kinematic properties of a wind field using a Doppler radar, J. Appl. Meteor., 7, 105-113, 1968.