Ceilometer (Vaisala CL51) data (*.dat) format

For more information, refer to "Ceilometer CL51 User's Guide".


First line (-2013-05-14 00:00:59) indicates time (UTC) when data 
were taken.


Second line (
CL010226) is data header. 


Third line (10 00420 ///// ///// 000000008080) is key data of cloud
base height. The meanings of each term are as follows.
 First two digits (10) 
  First digit shows status of detection ;
    0 : no significant backscatter
    1 : one cloud base detected
    2 : two cloud bases detected
    3 : three cloud bases detected
    4 : full obscuration determined but no cloud base detected
    5 : some obscuration detected but determined to be transparent
    / : Raw data input to algrithm missing or suspect
  Second digit shows warnings/alarm information ;
    0 : self-check OK
    W : at least one warning active, no alarms
    A : at least one alarm active

  1st term (00420)
   If detection is 1,2,or 3, then lowest cloud height.
   If detection is 4, then vertical visibility. 
   If detection is 0 or 5, then /////.

  2nd term (/////)
   If detection is 2 or 3, then second lowest cloud base height.
   If detection is 4, then highest signal detected.
   If detection is 0,1, or 5, then /////.
   *) Since first digit is 1 in this example, this term becomes /////.

  3rd term (/////)
   If detection is 3, then highest cloud base height.
   Otherwise, /////.

  Last term indicates alarm, warning, and internal status information.
  No description here.


4th line (  5 0041  0 ////  0 ////  0 ////  0 ////) is key data of cloud layer information.
The meanings of each term are as follows
 First digit (5) shows detection status
  0 - 8 : Cloud coverage of the first layer in octas
  9     : Vertical visibility
  -1    : Data missing, sky condition option not active or ceilometer in standby mode
  99    : Not enough data

 1st term (0041)
  Height of the 1st cloud layer (410m)
 
 2nd term (0)
  Cloud amount of the 2nd layer in octas
 
 3rd term (////)
  Height of the 2nd cloud layer
 
 4th term (0)
  Cloud amount of the 3rd layer in octas
 
 5rd term (////)
  Height of the 3rd cloud layer
 
 6th term (0)
  Cloud amount of the 4th layer in octas
 
 7rd term (////)
  Height of the 4th cloud layer
 
 8th term (0)
  Cloud amount of the 5th layer in octas
 
 9rd term (////)
  Height of the 5th cloud layer
 
 
5th line (00100 10 1540 100 +34 100 02 0015 L0032HN15 012) is measurement parameters.
  1st term (00100)
	Parameter SCALE; 100[%] is normal
  2nd term (10)
	Backscatter profile resolution in meters
  3rd term (1540)
	Length of the profile in sample
  4th term (100)
	Laser pulse energy [%]
  5th term (+34)
  	Laser temprature [deg-C]
  6th term (100) 
	Window transmission estimate, [%]
  7th term (02)
	Tilt angle, [deg] from vertival
  8th term (0015)
	Background light, [mV] at internal ADC input

  9th term (L0032HN15)
	Measurement parameters
	  L: pulse [L:Long/S:Short]
       0032: pluse qty
	  H: gain [H:Hight/L:Low]
	  N: bandwidth [N:Narrow/W:Wide] (Fixed:N)
	 15: sampling [15/30] MHz (Fixed:15)

  10th term (012)
	SUM of detected and normalized backscatter [12*10^-4=0.0012srad^-1]


6th line (ex.6th line: )
Backscatter profile, sensitivity and range normalized, at 10m resolution,
normally scaled to units of (10000*srad*km)^-1

	Start 	Byte	Sample [units]
	-----	----	------------------------
	1	5	000a2 [20-bit Hex]=162    , 10m sensitivity normalized backscatter.
	6	5	0009d [20-bit Hex]=157    , 20m sensitivity normalized backscatter.
	11	5	0009e [20-bit Hex]=158    , 30m sensitivity normalized backscatter.
	16	5	0009c [20-bit Hex]=156    , 40m sensitivity normalized backscatter.
	21	5	0008a [20-bit Hex]=138    , 50m sensitivity normalized backscatter.
	..	..	...
	..	..	...
	7696	5	0043e [20-bit Hex]=1086   , 15390m sensitivity normalized backscatter.
	7701	5	ff4fd [20-bit Hex]=-2819  , 15400m sensitivity normalized backscatter.


7th line (d146) is Checksum.


--- Example ---

-2013-05-14 00:00:59

CL010226
10 00420 ///// ///// 000000008080
  5 0041  0 ////  0 ////  0 ////  0 ////
00100 10 1540 100 +34 100 02 0015 L0032HN15 012
000a20009d0009e0009c0008a00091.....ffc950043eff4fd (5byte*1540)
d146



--- Example End ---