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process_soda2

To process 2D-S, HVPS, CIP, and PIP data, use the process_soda2 script.

 process_soda2 [--fast] [--verbose] [-vm] [project='Project Name'] [method='METHOD'] [processingtype='PROCESSINGTYPE']

It needs to be ran from the flight date directory (*/YYYYMMDD_HHMMSS). The flight date directory needs to include a PostProcessing directory which needs a *.basic.1Hz file within it. 2D-S and HVPS data are within their own directories within the flight date directory, and CIP and PIP data are within the PostProcessing directory.

Environment Variables

The following environment variables need to be set for proper processing:

 $ADPAA_DIR: the path to the ADPAA code (example: ADPAA_DIR=~/CoPAS/ADPAA)
 $CoPAS_DIR: the path to the SODA2 code (example: CoPAS_DIR=~/CoPAS)
 $PATH: needs to include the ${ADPAA_DIR}/bin (example: PATH=${ADPAA_DIR}/bin:${PATH})

The following environment variables are optional:

 verbose_mode: allows all output to be shown (including the IDL compiled modules and any SODA2 output)
 virtual_machine: uses compiled IDL code within ADPAA to process data using the IDL virtual machine (doesn't need IDL license, but code may not work for all process_soda2 processing)

Default SODA2 Processing Settings

Linkage scripts within ADPAA pass parameters to the included SODA2 software which determine the particle sizing method and additional sizing corrections, the method of processing partially captured particles, and other corrective procedures to be used during processing. Adjustments can be made within the initialize_structure.pro file found in the ADPAA/src/linkage_soda directory. The default settings and their alternatives are described below.

Methods for Processing Particle Size [method]

default: fastcircle; 
alternatives: WaterProcessing, xsize, ysize;  

• fastcircle - the smallest possible circle is fit around a particle image and the circle diameter is used at the particle diameter. Fastcircle is a computationally efficient method which helps produce a simple comparison of particle area to the area of a circle or "area ratio". Particles are rejected if the area ratio is less than 0.1, or the particle size is outside of the size-bin range.

• WaterProcessing - a method of applying "fastcircle" with the addition of stricter roundness criteria to only process particles that are liquid water, as well as a particle size correction factor based on the size of Poisson spots generated when imaging liquid particles. Poisson spots develop due to particle magnification as a result of improper particle placement within the probe's depth of field. When a Poisson spot is detected the area of the spot is measured and compared to to the total particle area. The resulting ratio produces a correction factor which reduces the measured particle size to that of the actual particle (without Poisson magnification). More information on Poisson spot size correction can be found in Korolev (2007), DOI https://doi.org/10.1175/JTECH1980.1. Particles are rejected if the area ratio is less than 0.4 (or less than 0.5 if the particle is 10 or more pixels in size), if the size is greater than 6 mm, or if the corrected particle size is outside of the size-bin range.

• xsize - the maximum difference between shaded pixels is measured across the array (the x plane). Xsize is particularly useful for spinning disc calibrations.

• ysize - the maximum difference between shaded pixels is measured along the direction of airflow (the y plane).

Methods for Processing Partially Captured Particles [processingtype]

default: reconstruction; 
alternatives: allin, centerin;

• reconstruction - not fully captured or touching the edge of the array have the missing component recreated using the equations of Heymsfield and Parrish 1978, with the probe sample area adjusted according to Equation 18 of the aforementioned article. More information can be found in Heymsfield and Parrish 1978, DOI https://journals.ametsoc.org/doi/pdf/10.1175/1520-0450%281978%29017%3C1566%3AACTFIT%3E2.0.CO%3B2.

• allin - particles are only processed if they are fully imaged and do not touch an array edge.

• centerin - particles are only processed if the geometric center of the particle is contained within the image. More information can be found in Heymsfield and Parrish 1978, DOI https://journals.ametsoc.org/doi/pdf/10.1175/1520-0450%281978%29017%3C1566%3AACTFIT%3E2.0.CO%3B2. This method is the default for SODA2 software.

Other Settings and Corrective Procedures

• endbins - the range of bins used to record particle information, default [5,15,25,35,45,55,65,75,85,95,105,125,145,175,225,275,325,400,475,550,625,700,800,900,1000,1200,1400,1600,1800,2000].

• fixedtas - the true air speed of the plane is set to a specific value rather than read in from the data files, default off.

• inttime_reject - apply particle shattering correction using particle interarrival times (more information can be found in Field et al. 2006, DOI https://doi.org/10.1175/JTECH1922.1), default on.

• project - the name of the project to be used in the particle images and idl routines, default 'UND-North Dakota'.

• stuckbits - correct for errors generated by diodes that are continuously on or off using their neighboring diodes, default off.

• timeoffset - the time in seconds to be added to the probe data if the data acquisition computer clock was incorrect, default 0.