PMS-2D Processed Data Description

Description of variables available in the netCDF file.

The PMS-2D probes produce 4 kilo-byte records of image data and a single value called shadow-or.  The shadow-or produces a single concentration and the image data is converted into two sets of size-distributions and associated derived quantities.

 

Shadow-or (SHDORC and/or SHDORP)

The shadow-or is a total count of particles received by the probe.  There is no sizing information and no particle is lost, unlike the image data, where data is lost due to the high collection rate of the probe and the slower download rate of data acquisition systems.  Derived concentrations are produced from these variables.

CONC2C is derived from SHDORC (2D-C).

CONC2P is derived from SHDORP (2D-P).

 

Entire-in counts histogram (A1DC and DT1DC)

The first histogram produced is the entire-in algorithm; this emulates the 260X probe.  DT1DC (and DT1DP) is the dead-time associated with this time interval, it is the accumulation of overload and time consumed by rejected particles.  DT1DC is used to reduce the sample-volume.

Rejection criteria:

  • Any particle touching an edge diode.
  • There must be at least 1 visible shadowed diode.  i.e. zero area image particles are rejected.
  • Particle height must be less than 4 times length (along flight path).

Particle size is simply the height of any particle that passed the above.

C1DC is the size-distribution derived from A1DC.  C1DC then leads to CONC1DC, DBAR1DC, DISP1DC, PLWC1DC and DBZ1DC.

C1DP is the size-distribution derived from A1DP.  C1DP then leads to CONC1DP, DBAR1DP, DISP1DP, PLWC1DP and DBZ1DP.

 

Center-in counts histogram (A2DC and DT2DC)

The second histogram produced is based on the center-in algorithm.  DT2DC (and DT2DP) is the dead-time associated with this time interval, it is the accumulation of overload and time consumed by rejected particles.  DT2DC is used to reduce the sample-volume.

Rejection criteria:

  • Any particle with length (along flight path) exceeding 121 diodes.
  • Height is less than 24 diodes and length is greater than 6 times height.
  • Height is less than 6 diodes and length is greater than 3 times height.
  • If an edge diode is touched then length must be greater than 1/2 height (center-in).

Particle size is then the maximum of height vs. length.

C2DC is the size-distribution derived from A2DC.  C2DC then leads to CONC2DC, DBAR2DC, DISP2DC, PLWC2DC and DBZ2DC.

C2DP is the size-distribution derived from A2DP.  C2DP then leads to CONC2DP, DBAR2DP, DISP2DP, PLWC2DP and DBZ2DP.