Informal Transcript for the Ewan Crosbie Cloud Water Collector
Clouds are one of the most important aspects of climate and we need to understand how clouds work better. You know, we have instrumentation that can measure physical properties of clouds, but actually being able to collect samples of the cloud water we’re flying through to analyze the chemistry of those cloud droplets is an important part of the puzzle that we haven’t yet been able to do in this mission.
People have collected cloud water. I mean, clearly when the aircraft flies through clouds, the airframe collects water. Unfortunately, that fine detail that we’re trying to tease out from the cloud chemistry is lost when you contaminated (it) with everything that the aircraft has been picking up through its flight. So the idea here is essentially it’s a control. We have a way of controlling what we take in as cloud water and we try to reject the stuff that we don’t want to include.
The clouds we are measuring here are what is known as boundary layer clouds. And that’s really what’s important for the NAAMES mission, is understanding those low boundary layer clouds over water. So these clouds, essentially, have a fairly well defined profile of liquid water.
As you go higher, the cloud gets generally thicker so there is more cloud water available. Down at the bottom of the cloud, the cloud droplets aren’t as large and there’s not as much cloud water available for collection. But we want to target both of those regions, both the cloud base and the cloud top, because even though the cloud base is harder to get a large volume of cloud water collected, it has interesting information about the aerosols that were involved in activating those cloud water droplets.
The top of the cloud, it’s juicier, there’s more liquid water content available for us to collect, but, essentially, it’s potentially more dilute. The interesting thing is we know how the water mass changed vertically, but if the concentrations show something different, that’s essentially information about chemistry that’s happening within the cloud, which is one of the areas of study that I’m really interested in trying to understand better.
What we’re trying to understand is the small amount of impurities that are in the cloud. They may have come from locally produced, in-situ production of these species in the cloud water through this wet chemistry, if you like, in the cloud. Or it could have been dry chemistry below the cloud, so it didn’t need the cloud to actually perform that chemical reaction. We’re measuring below the cloud. We know what the composition of aerosol and gases are below the cloud. With this cloud water we add another piece of the puzzle to try and understand other things, like sulfate chemistry, which is an important aspect of this study.
The idea is that within the clouds you have gasses, you have aerosols, and you have activated aerosol particles that are the cloud droplets. The chemistry becomes that much more difficult when you have this phase change. You have liquid water in abundance and it acts as a new medium where chemical reactions can take place.
When you’re out of the cloud, you don’t have that. So that’s an experiment we’ll do off-line, so now that we’ve collected this cloud water, it’s going to be done with Luke, we’ll set up an experiment in the lab and, again, it’s a new technique, and I don’t believe that anybody has looked at biological particles in cloud water in this way, certainly in connection with a mission such as NAAMES, where there is a strong focus on ocean and aerosols interactions and then how that interacts with clouds, so this is a new thing.
We’ve had requests to use the cloud water that we collect during this missions to supplement other investigators’ work. People who are outside of my knowledge in biology have taken an interest in the cloud water to do their analysis, particularly the kind of analyses that are done on seawater, and use that as a comparison to see whether stuff comes off the ocean and makes it up into clouds and how it affects the clouds.
It’s a tracer, essentially. The nice thing about using those biological particles is that they are a tracer that doesn’t necessarily change in the same way that chemical tracers change. Chemical tracers can evolve and react into other species, but these biological tracers are somewhat inert in that sense, to chemical transformations. That’s another exciting new technique that we may do to try and understand the connection between the clouds locally- and potentially regionally-transported particles that affect clouds.
This probe that hangs down here is called the AC3, the axial cyclone cloud water collector. This is the new prototype collector for collecting in situ cloud water. In the inside of the probe, the stator, which basically generates that swirl, it is made out of stainless steel. The rest of the probe is aluminum. To make that part of aluminum using conventional milling would have been very, very difficult and taken a long time and been very costly. We used an experimental technique. It’s a steel powder that we start off with, and it’s a process called laser sintering. Essentially the laser melts the steel powder and builds the shape in the same way that a printer would except that it’s three-dimensional. Essentially, it’s 3-D printing but for steel.