The Depolarization and Backscatter - Unattended Lidar (DABUL) is a pulsed laser-radar operating at 523 nm wavelength.  Range resolution is 30 m, and time resolution is as short as 1 s. This lidar system uses a low energy laser with high repetition rates for good sensitivity while being completely eyesafe. 

Data are collected in four channels according to receiver field of view and polarization detected:  far parallel, far perpendicular, near parallel, and near perpendicular.  The far channel has greater sensitivity and a narrower field of view than the near channels.  Linear polarization is transmitted, and parallel and perpendicular refer to the polarization detected.  The depolarization ratios are obtained by taking the ratio of the perpendicular to parallel channels in either the near or far channels.  The far parallel lidar return is the field represented here, and the far parallel and far perpendicular channels are used to calculate the depolarization ratios.  

The FINAL data set provided here contains three products:  

a.) Lidar returned-power time-height images in gif format
b.) linear depolarization ratio time-height images in gif format
c.) cloud boundary time-height data in ASCII format.  

All of these final products have been averaged for 10 minutes.  All products are available for the dates of Nov. 
1 through Aug. 7, 1998, with the exception of the following periods:

1.) February 2 -13, offline due to heater repair
2.) July 5 - 10, offline due to shutter disabling
3.) Aug. 8,  laser failure, end of lidar SHEBA data set

a.) Range-time plots of the far-parallel channel intensity presented here have been corrected as follows:
	Nov. 1 thru Dec. 1 --Background, Heater Cycle, Afterpulse, Range and Overlap	
	Dec. 2 --Background, Afterpulse, Range and Overlap	
	Dec. 3, 4 --Background, Heater Cycle, Afterpulse, Range and Overlap	
	Jan. 1 - Aug. 7 --Background, Afterpulse, Range and Overlap

b.)  Range-time plots of the linear depolarization ratio (far perpendicular channel divided by far parallel channel)  illustrate cloud phase. Generally, low values for the depolarization depolarization indicate 	spherical particles (water or aerosols). Depolarization ratios greater than 0.1 indicate shaped particles (ice phase). 
        
c.) The cloud boundary determination was obtained by simply thresholding the Far Parallel Intensity and Depolarization values for cloud base and top height.  They contain cloud information derived from processing the DABUL lidar measurements.  The files span observations made from 1 November 1997 through 8 August 1998.  The lidar samples are obtained every 5 s but were averaged to 10 minutes for the cloud products presented here.  
All times are in UTC and all heights are in meters.

The CLD file names reflect the date and time for that file and in general there is 
one file per each day.  The files contain the following information in order of 
appearance;
year, month, day, hour, minute, second, number of layers, cloud base height, 
cloud top height, average intensity, average depol ratio, integrated depol ratio
 
 Additional information or questions pertaining to the DABUL system should be directed to Dr. Raul Alvarez (ralvarez@etl.noaa.gov) and for information regarding the data fields or processing please contact Janet Intrieri (jintrieri@etl.noaa.gov) or Wynn Eberhard (weberhard@etl.noaa.gov). 

Additional information as well as examples of DABUL measurements can be found on
our web site:

 http://www2.etl.noaa.gov

and also at http://www6.etl.noaa.gov/projects/fireace.html