Macquarie Island Cloud Condensation Nuclei Concentrations
Authors: 
- Ruhi S. Humphries (Ruhi.Humphries@csiro.au)
- Melita D. Keywood
- Jason Ward
- Simon Alexander

ACRE_CCN_1H_FINAL.h5 file contains Cloud Condensation Nuclei (CCN) measured using a DMT CCN-100 instrument. 
The instrument was run between March 2016 and March 2018 in the Clean Air laboratory on Macquarie Island, Australia (54o30'0?S 158o57'0?E).

The instrument was run on a cycle of supersaturations, which changed a number of times throughout the measurement program (see details below).

Data processing:
- Data was filtered for maintenance periods and instrument issues. Most significantly, the instrument's internal nafion failed 
in the second year of measurements, resulting in the removal of data between 25 April and 17 July 2017.
- Obvious significant spikes in data were removed as these were likely the result of station activity resulting in anthropogenic emissions.
- Data was filtered for when the instruments parameters were out of specification, and for 3 minutes after each change in supersaturation 
(necessary to allow the system to come to equilibrium)
- The supersaturations were corrected for changes in atmospheric pressure between the measurement site and the calibration site (Boulder, Colorado).
No statistical filtering was performed.


Data quality:
- The onboard instrument PC had clock issues, resulting in time drifting up to a minute from true time between time sync events. 
Data which exhibits this problem should be used appropriately with this in mind. This issue will be addressed in a future version of the data.
- There was no obvious contamination from the nearby station based on wind direction and CCN data, however suspicious variability in the aerosol
data suggest local influence and possible contamination. This is best remove by comparing with CN data, which is more sensitive to pollution. 
Because of the instrument time issues, this filtering has not yet been performed.


Data columns are listed with the following supersaturations (ss): 0.2504, 0.3504, 0.4504, 0.5504, 0.6504, 1.0504
ccn_<ss>_avg - the mean value for the hour
ccn_<ss>_count - the number of values used to calculate the statistics for this hour
ccn_<ss>_mad - median absolute deviation
ccn_<ss>_med - median
ccn_<ss>_std - standard deviation 
ccn_<ss>_rmsn - square root of the sum of squares (root mean square numerator)

Note that because the instrument cycles through supersaturations each hour, each of these "hourly" values, represents only approximately 
7 minutes of measurements (after the 3 minutes of data removal) in each hour. In the Southern Ocean, this is reasonable because concentrations
generally only change on the hourly time-scale because of disperse, distance sources.

Supersaturation settings were changed throughout the campaign such that they were available between the following dates:
0.2504 - Mar - Nov 2016 one measurement per day; Nov 2016 - Mar 2018 one measurement per hour
0.3504 - Mar 2016 - Mar 2018 one measurement per hour
0.4504 - Mar - Nov 2016 one measurement per day; Nov 2016 - Mar 2018 one measurement per hour
0.5504 - Mar 2016 - Mar 2018 one measurement per hour
0.6504 - Mar - Nov 2016 one measurement per day; Nov 2016 - Mar 2018 one measurement per hour
1.0504 - Mar - Nov 2016 one measurement per day; Nov 2016 - Mar 2018 one measurement per hour