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Flash-Freezing Cloud Water!


Brianna and Chris drove up to Whiteface Mt to assist with calibrating the CCN counter and to do some testing of the cloud water chemistry as a function of time during storage (by flash-freezing a subset of the samples at regular intervals). Cloud water samples are typically kept just above freezing in a refrigerator and then stored in a freezer (where they take several more hours to freeze solid) as they await chemical analysis. Flash freezing a 250mL sample in liquid nitrogen (LN2) takes a few minutes, we found out. As far as we know, flash freezing hasn't been done with cloud water samples at WFM before. This was suggested to us by colleagues at UC Davis and U Mich.


The main safety concern is not to splash the LN2 on yourself when pouring and to operate in a well-ventilated space.


So far we have mainly frozen test samples that we sprayed on the cloud water collector (to mimic the conditions that cloud water is exposed to, potentially including any bacterial contaminants that might have been picked up in the wind). These spray tests allow us to know what the cloud water composition "should be", and we can see how the measurements change over time after being exposed to different conditions during collection and storage. We've done a few rounds of these spray tests this summer, but this is the first time we've tried flash-freezing.

On this day, the clouds were actually below the summit, but were occasionally pushed over the top of the mountain due to orographic lift (as a result of the mountain's presence)




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