DOI: 10.5061/dryad.kprr4xhb2
title: Data for: Low temperature ice nucleation of sea spray and secondary marine aerosols under cirrus cloud conditions

description: Sea spray aerosols (SSA) represent one of the most abundant aerosol types
 on a global scale and have been observed at all altitudes including the
 upper troposphere. SSA has been explored in recent years as a source of
 ice nucleating particles (INPs) in cirrus clouds due to the ubiquity of
 cirrus clouds and the uncertainties in their radiative forcing. This study
 expands upon previous works on low temperature ice nucleation of SSA by
 investigating the effects of atmospheric aging of SSA and the ice
 nucleating activity of newly formed secondary marine aerosols (SMA) using
 an oxidation flow reactor. Polydisperse aerosol distributions were
 generated from a Marine Aerosol Reference Tank (MART) filled with 120 L of
 real or artificial seawater and were dried to very low relative humidity
 to crystallize the salt constituents of SSA prior to their subsequent
 freezing, which was measured using a Continuous Flow Diffusion Chamber
 (CFDC). Results show that for both primary SSA (pSSA), and the aged SSA
 and SMA (aSSA+SMA) at temperatures &gt; 220 K, homogeneous conditions
 (92–97 % relative humidity with respect to water (RHw)) were required to
 freeze 1 % of the particles. However, below 220 K, heterogeneous
 nucleation occurs for both pSSA and aSSA+SMA at much lower RHw, where up
 to 1 % of the aerosol population freezes between 75–80 % RHw. Similarities
 between freezing behaviors of the pSSA and aSSA+SMA at all temperatures
 suggest that the contributions of condensed organics onto the pSSA or
 alteration of functional groups in pSSA via atmospheric aging did not
 hinder the major heterogeneous ice nucleation process at these cirrus
 temperatures that has previously been shown to be dominated by the
 crystalline salts. Occurrence of 1% frozen fraction of SMA, generated in
 the absence of primary SSA, was observed at/near water saturation below
 220 K, suggesting it is not an effective INP at cirrus temperatures,
 similar to findings in the literature of other organic aerosols. Thus, any
 SMA coatings on the pSSA would only decrease the ice nucleation behavior
 of pSSA if the organic components were able to significantly delay water
 uptake of the inorganic salts, and apparently, this was not the case.
 Results from this study demonstrate the ability of lofted primary sea
 spray particles to remain an effective ice nucleator at cirrus
 temperatures, even after atmospheric aging has occurred over a period of
 days in the marine boundary layer prior to lofting. We were not able to
 address aging processes under upper tropospheric conditions.
description: **README for “Low Temperature Ice Nucleation of Sea Spray and Secondary
 Marine Aerosols under Cirrus Cloud Conditions”**   Ryan Patnaude
 Postdoctoral Fellow Colorado State University Department of Atmospheric
 Science 1371 Campus Delivery, Fort Collins, CO 80526
 ryan.patnaude@colostate.edu
 [https://orcid.org/0000-0003-3129-8279](https://orcid.org/0000-0003-3129-8279)   **1.0        Data Set Overview**   These measurements were from experiments conducted at Colorado State University to better understand the ice nucleating ability of sea spray and secondary marine aerosols at cirrus cloud temperatures. This archive is for the Colorado State University continuous flow diffusion chamber (CFDC) instrument, and aerosol particle data from aerodynamic particle sizer (APS) and scanning mobility particle sizer (SMPS) instruments. The experiments were conducted between March 3<sup>rd</sup> and March 17<sup>th</sup> of 2021.   Experimental days: 03/04/2021 – 03/04/2021: Artificial seawater (ASW) with oxidized particles. 03/07/2021 – 03/08/2021: ASW with primary emitted particles. 03/09/2021: Artificial seawater with secondary marine aerosols (SMA). 03/10/2021: DI water blank test. 03/12/2021 – 03/13/2021: Seawater (SW) with primary emitted particles. 03/14/2021 – 03/15/2021: SW with oxidized particles 03/16/2021: SW with SMA.   **2.0        Instrument Description:**   The Colorado State University (CSU) Continuous Flow Diffusion Chamber (CFDC) is an ice-thermal gradient diffusion chamber that optically detects the freezing of single aerosol particles from air after exposure to controlled temperature and humidity conditions, including following liquid cloud particle activation. The operating principles of the vertically-oriented, cylindrical-walled CFDC is described in the earlier works of Rogers (1988), Rogers et al. (2001) and were modified to measure at temperatures down to -70 ºC (Patnaude et al., 2021).   **3.0 Data Format:**   CFDC data are reported in standard .csv format. The list of variables and units are given in the data file header but are repeated here.   **Time (sec),** (second), seconds of the day past midnight MST **Total Flow Ctrlr Output,** (standard liters per minute) – control setting for column total flow **Sheath Flow Ctrlr Output,** (standard liters per minute) – control setting for column sheath flow **Chamber Pressure,** (hectopascal) – pressure inside of CFDC column **Inlet Filter**, (unitless) – inlet filter on/off variable (0 for off filter, 1 when pulling on filter) **Sheath Flow SP (slpm),** (standard liters per minute) – standard sheath flow inside CFDC **Sheath Flow SP (vlpm)**, (volumetric liters per minute) – volumetric sheath flow inside CFDC **Total Flow SP (slpm),** (standard liters per minute) – standard total flow inside CFDC **Total Flow SP (vlpm)**, (volumetric liters per minute) – volumetric total flow inside CFDC **Bin1-Bin256**, (counts per second) – particle counts for each OPC size channel **Inlet Flow (vlpm), (**volumetric liters per minute) – volumetric flow at the inlet of the CFDC **Avg Lam Temp (C),** (Celsius) – average CFDC column temperature **Avg Lam SSw (%),** (percent) – average CFDC column supersaturation with respect to water **Avg Lam SSi (%),** (percent) – average CFDC column supersaturation with respect to ice **Residence Time (s),** (second) – residence time of airflow inside CFDC   The CFDC file names archived are:   CFDC003\_20220303112824\_aSSA\_SMA\_ASW.csv CFDC003\_20220304000000\_aSSA\_SMA\_ASW.csv CFDC003\_20220307000000\_ pSSA\_ASW.csv CFDC003\_20220308085308\_ pSSA\_ASW.csv CFDC003\_20220309143831\_SMA\_ASW.csv CFDC003\_20220310000000\_DI.csv CFDC003\_20220312000000\_pSSA\_SW.csv CFDC003\_20220313000000\_pSSA\_SW.csv CFDC003\_20220314115342\_aSSA\_SMA\_SW.csv CFDC003\_20220315000000\_aSSA\_SMA\_SW.csv CFDC003\_20220316000000\_SMA\_SW.csv   APS data are reported in standard .txt format. The list of variables and units are given in the data file header and repeated below. APS data are reported for APS1 and APS2, which refers to the location of the instrument, either upstream and downstream of the MART, respectively. Please refer to the manuscript section 2.1 for a more detailed description of the experimental configuration.   **Sample** (unitless) – Sample number of the current data sample. **Date, (**MM/DD/YY) – standard date format **Start Time**, (mountain standard time) – start time of the APS data collection **Aerodynamic Diameter,** (micron) – aerodynamic particle diameter for each size bin **dN/dlogDp,** (number per cubic cm) – particle counts for each size bin **Total Flow**, (liters per minute) - the total flow rate of the sample aerosol **Sheath Flow**, (liters per minute) - the flow rate of the outer nozzle (sheath) flow **Laser Power**, (percent) - percent of laser power used from 0 to 100%. Default is 75% **Laser Current,** (milliamp) – laser current between 0 and 100 **Status Flags**, (unitless) – instrument status flags. If no flags are set, the message “No Errors Detected” is displayed   The APS file names archived are:   APS1\_aSSA\_SMA\_ASW\_030322.TXT APS1\_aSSA\_SMA\_ASW\_030422.TXT APS1\_aSSA\_SMA\_SW\_031422.TXT APS1\_aSSA\_SMA\_SW\_031522.TXT APS1\_DI\_031022.TXT APS1\_pSSA\_ASW\_030722.TXT APS1\_pSSA\_ASW\_030822.TXT APS1\_pSSA\_SW\_031222.TXT APS1\_pSSA\_SW\_031322.TXT APS1\_SMA\_ASW\_030922.TXT APS1\_SMA\_SW\_031622.TXT APS2\_aSSA\_SMA\_ASW\_030322.TXT APS2\_aSSA\_SMA\_ASW\_030422.TXT APS2\_aSSA\_SMA\_SW\_031422.TXT APS2\_aSSA\_SMA\_SW\_031522.TXT APS2\_DI\_031022.TXT APS2\_pSSA\_ASW\_030722.TXT APS2\_pSSA\_ASW\_030822.TXT APS2\_pSSA\_SW\_031222.TXT APS2\_pSSA\_SW\_031322.TXT APS2\_SMA\_ASW\_030922.TXT APS2\_SMA\_SW\_031622.TXT   SMPS data are reported in standard .txt format. The list of variables and units are given in the data file header and repeated below. SMPS data are reported for SMPS1 and SMPS2, which refers to the location of the instrument, either upstream and downstream of the MART, respectively. Please refer to the manuscript section 2.1 for a more detailed description of the experimental configuration.   **Sample** (unitless) – Sample number of the current data sample. **Date,** (MM/DD/YY) – standard date format **Start Time**, (mountain standard time) – start time of the APS data collection **Diameter Midpoint, (**counts per cubic cm) – particle diameter defining each size bin and particle counts for each size bin **Title status flag**, (unitless) – instrument status flag   The SMPS file names archived are:   SMPS1\_aSSA\_SMA\_ASW\_030422.TXT SMPS1\_aSSA\_SMA\_SW\_031422.TXT SMPS1\_aSSA\_SMA\_SW\_031522.TXT SMPS1\_DI\_031022.TXT SMPS1\_pSSA\_ASW\_030722.TXT SMPS1\_pSSA\_ASW\_030822.TXT SMPS1\_pSSA\_SW\_031222.TXT SMPS1\_pSSA\_SW\_031322.TXT SMPS1\_SMA\_ASW\_030922.TXT SMPS1\_SMA\_SW\_031622.TXT SMPS2\_aSSA\_SMA\_ASW\_030322.TXT SMPS2\_aSSA\_SMA\_ASW\_030422.TXT SMPS2\_aSSA\_SMA\_SW\_031422.TXT SMPS2\_aSSA\_SMA\_SW\_031522.TXT SMPS2\_DI\_031022.TXT SMPS2\_pSSA\_ASW\_030722.TXT SMPS2\_pSSA\_ASW\_030822.TXT SMPS2\_pSSA\_SW\_031222.TXT SMPS2\_pSSA\_SW\_031322.TXT SMPS2\_SMA\_ASW\_030922.TXT SMPS2\_SMA\_SW\_031622.TXT   **3.0 Code/Software:**   All data processing and figure plotting was conducted using MATLAB scripts that are listed below. Use of these script require a proprietary license with the base package of MATLAB. Please refer questions on using these scripts to the email listed above. The majority of the MATLAB scripts listed below are functions that are run through the **CFDC\_import\_process.m** script   The file names archived are:   **CFDC\_import\_process.m** – *master script that loads in CFDC, APS and SMPS data for functions listed below.* **calc\_opc\_background.m** – *function to calculate the background aerosol distribution for ice particle calculation in IN\_RH\_space\_MART.m* **cfdc\_opc\_particle\_size\_dist.m** – *plots CFDC optical particle counter data for different temperature and relative humidity. (Figure 3)* **cfdc\_scan\_plot\_MART.m** – *function that plots the CFDC relative humidity scans (Figure 5)* **import\_APS\_files\_RJP.m** – *function that imports APS data in* import\_SMPS\_APS\_calc\_particle\_conc.m **import\_APS\_files.m** – *function that imports APS data in SizeDist.m* **import\_SMPS\_APS\_calc\_particle\_conc.m** *– function that imports SMPS and APS data in IN\_RH\_space\_MART.m* **import\_SMPS\_files\_RJP.m** – *function that imports SMPS data in* import\_SMPS\_APS\_calc\_particle\_conc.m **import\_SMPS\_files.m** – *function that imports SMPS data in SizeDist.m* **IN\_RH\_space\_MART.m** *– function in CFDC\_import\_process.m that calculate the ice active fraction used for Figures 6 and 7.* **OPC\_bins\_RHscans.m** \- \(used for Figure S3\) **SizeDist.m** *– script that imports SMPS and APS data to plot size distributions shown in Figure 4*   **4.0 References**   Patnaude, R. J., Perkins, R. J., Kreidenweis, S. M. and DeMott, P. J.: Is Ice Formation by Sea Spray Particles at Cirrus Temperatures Controlled by Crystalline Salts?, ACS Earth Sp. Chem., 5(9), 2196–2211, doi:10.1021/acsearthspacechem.1c00228, 2021.   Rogers, D. C.: Development of a continuous flow thermal gradient diffusion chamber for ice nucleation studies, Atmospheric Research, 22(2), 149-181, doi:10.1016/0169-8095(88)90005-1, 1988.   Rogers, D. C., P. J. DeMott, S. M. Kreidenweis and Y. Chen: A continuous flow diffusion chamber for airborne measurements of ice nuclei, J. Atmos. Oceanic Technol., 18, 725-741, doi:10.1175/1520-0426(2001)018&lt;0725:ACFDCF&gt;2.0.CO;2, 2001.