Title: SOCRATES 2D-S PSD Product

Author(s):

Wei Wu
Research Scientist, 
Cooperative Institute for Mesoscale Meteorological Studies, 
University of Oklahoma
National Weather Center, Suite 2100
120 David L. Boren Blvd.
Norman, OK 73072
Phone: (405)325-4637
Email: weiwu@ou.edu
ORCID:0000-0002-4363-1094
Website: weiwu.oucreate.com

Greg M. McFarquhar
Director, 
Cooperative Institute for Mesoscale Meteorological Studies
Professor, 
School of Meteorology
University of Oklahoma
National Weather Center, Suite 2100
120 David L. Boren Blvd.
Norman, OK 73072
Phone: (405) 325-3041
Email: mcfarq@ou.edu 
ORCID: 0000-0003-0950-0135
Website: mcfarq.oucreate.com

1.0 Data Set Overview:

The dataset includes Research Flight #1 conducted on Jan 15, 2018 to Research Flight #15 conducted on Feb 24, 2018 over Southern Ocean during SOCRATES field campaign. 

2.0 Instrument Description:

2DS is an optical array probe with 128 photodiodes with resolution of 10 micrometers. 

3.0 Data Collection and Processing:

Data is collected by SPEC 2D-S probe installed on NCAR G-V during SOCRATES field campaign. The University of Illinois/Oklahoma Optical Array Probe Processing Software (UIOOPS) was used to process the raw image data. The derived variables include cloud particle size distributions (PSDs) and bulk properties, such as total number concentration, liquid water content and ice water content (see section 4.0 for a complete list). Data has been intercompared with EOL products for quality control.

4.0 Data Format:

Data is in netCDF4 format with built-in compression. The PSDs and bulk properties are provided at 1 Hz frequency. The data have two dimensions: time (named Time) and bins (named CIPcorrlen). The list of variables are: 

	double IWC(Time) ;
		IWC:units = "g/m3" ;
		IWC:long_name = "Ice Water Content using m-D relations for ice particles >= 200 um" ;
		IWC:short_name = "IWC" ;
	double IWC_BL(Time) ;
		IWC_BL:units = "g/m3" ;
		IWC_BL:long_name = "Ice Water Content using Baker and Lawson method for ice particles >= 200 um" ;
		IWC_BL:short_name = "IWC_BL" ;
	double Nice(Time) ;
		Nice:units = "cm-3" ;
		Nice:long_name = "number concentration for ice partciles >= 200 um" ;
		Nice:short_name = "Nice" ;
	double Nt(Time) ;
		Nt:units = "cm-3" ;
		Nt:long_name = "number concentration for all partciles >= 4 pixels" ;
		Nt:short_name = "Nt" ;
	double TWC(Time) ;
		TWC:units = "g/m3" ;
		TWC:long_name = "Total Water Content using m-D relations for all particles >= 4 pixels" ;
		TWC:short_name = "TWC" ;
	double TWC_BL(Time) ;
		TWC_BL:units = "g/m3" ;
		TWC_BL:long_name = "Total Water Content using Baker and Lawson method for all particles >= 4 pixels" ;
		TWC_BL:short_name = "TWC_BL" ;
	double bin_dD(CIPcorrlen) ;
		bin_dD:units = "millimeter" ;
		bin_dD:long_name = "bin size" ;
		bin_dD:short_name = "bin size" ;
	double bin_max(CIPcorrlen) ;
		bin_max:units = "millimeter" ;
		bin_max:long_name = "bin maximum size" ;
		bin_max:short_name = "bin max" ;
	double bin_mid(CIPcorrlen) ;
		bin_mid:units = "millimeter" ;
		bin_mid:long_name = "bin midpoint size" ;
		bin_mid:short_name = "bin mid" ;
	double bin_min(CIPcorrlen) ;
		bin_min:units = "millimeter" ;
		bin_min:long_name = "bin minimum size" ;
		bin_min:short_name = "bin min" ;
	double conc_all(Time, CIPcorrlen) ;
		conc_all:units = "cm-4" ;
		conc_all:long_name = "Size distribution using Dmax for all particles" ;
		conc_all:short_name = "N(Dmax)" ;
	double conc_ice(Time, CIPcorrlen) ;
		conc_ice:units = "cm-4" ;
		conc_ice:long_name = "Size distribution using Dmax for ice particles" ;
		conc_ice:short_name = "N(Dmax)" ;
	double time(Time) ;
		time:units = "HHMMSS" ;
		time:name = "Time" ;


5.0 Data Remarks:

This is the final PSD and bulk properties data for 2D-S probe. For PSDs of all particles, it is recommended to used PSDs for particles equal or larger than 40 um. For PSDs of ice particles, particle size equal or larger than 200 um should be used. The phase of cloud particles with size smaller than 200 um can not be distinguished due to the limited pixels.  

Version 1.1 fixed TAS issues for 2DS on RF02 and RF06. The Nt and Nice variables in all flights in V1.0 was output incorrectly, and fixed in Version 1.1. 

6.0 References:

Wu, W. and McFarquhar, G.M., 2016. On the impacts of different definitions of maximum dimension 
    for nonspherical particles recorded by 2D imaging probes. Journal of Atmospheric and Oceanic 
    Technology, 33(5), pp.1057-1072.