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Figure 4: Daily average CCN concentrations at 4 supersaturations for 40 days between 1 <br />June and 27 July, 2005 at Stanley. <br />These are higher values with a wider range of variability than reported by Detwiler et al <br />-3 <br />(2005). In that limited sample, concentrations ranged from 30 to 200 cm at a <br />supersaturation of 0.4%. It is to be expected that there will be a larger difference between <br />minimum and maximum values in a larger sample. But the 2005 values are generally <br />higher than the 2004 values at equivalent supersaturation. In Figure 4, the lowest <br />-3- <br />concentration active at 0.3% supersaturation is 98 cm and the lowest at 0.5% is 166 cm <br />3 <br />. As noted in Detwiler et al (2005) an instrument substitution was made at the last <br />minute in 2004, and the supersaturation achieved by the substitute instrument at the cloud <br />chamber temperature difference used was never verified by laboratory tests. In addition, <br />there was some uncertainty in the sample volume. We feel that the day-to-day variability <br />in concentration seen in the 14-day sample from 2004 is representative of the true <br />variability over that more limited period, but that the concentrations are most likely low. <br />The instrument used in 2005 is much better calibrated and its concentrations should be <br />considered more reliable. <br />Trajectory analyses: <br />As in Detwiler et al. (2005), an analysis of 3-day back trajectories arriving at the <br />sampling site at 12 PM local time was performed for each of the 40 days with good <br />7 <br />