A Post for International Women's Day

So today is the hundreth international women's day. I was alerted to this by many different forums asking for suggestions of influential women in science, which got me thinking...I realised that I couldn't even name an influential female in the field of atmospheric science never mind tell you what their contribution was. I knew people whose work I had come across, whose research or attitude had impressed or inspired me but I wanted someone that would be widely accepted as an exceptional scientist...and if there was such a person shouldn't I have heard of them? So I asked around the people in my office to see if they could name any. Thankfully they seemed better educated than me and gave me two names to research, Susan Solomon and Julia Slingo.

Allegedly, Susan Solomon's interest in science began when watching The Undersea World of Jacques Cousteau however it wasnt biology she went on to study but atmospheric chemistry. She completed her PhD in 1981 at the University of California at Berkeley and then joined the National Oceanic and Atmospheric Administration (NOAA). The work that she is most famous for was her contribution to studies of the Antarctic ozone hole. She theorised that polar stratospheric clouds would provide solid surfaces on which the reactions of CFCs which destroy ozone could take place. The presence of a surface on which atoms can be immobilised greatly increases the rate at which these ozone destroying reactions can take place.

Polar stratospheric clouds

In August 1986 Solomon led an expedition to McMurdo Base, Antarctica to study the formation of the ozone hole. Not satisfied with just one trip she led another expedition in 1987 and from the two gathered enough measurements to show that chlorine dioxide was present at much greater concentrations than predicted, the first physical evidence pointing to chlorine chemistry as the cause of the ozone hole. Since then she has continued research at NOAA and was a co-chair of the Science Working Group I of the Intergovernmental Panel on Climate Change (IPCC). She has gained many awards for her work including the international Blue Planet Prize in 2004 and a share in the 2007 Nobel Peace Prize, she has even had an Antarctic glacier named after her.

The icebreaker USCGC Glacier approaching Winter Quarters Bay at McMurdo station, Antarctica 

Professor Julia Slingo is also an important figure in atmospheric science. She is now the Met Office Chief Scientist and before that she was the Director of Climate Research in NERC's National Centre for Atmospheric Science. Her background is in climate modelling and her research focuses on tropical climate variability and its influence and response to climate change. In 2006 she founded the Walker Institute for Climate System Research at the University of Reading. She was involved with the IPCC fourth assessment on climate change and in 2008 became the first woman President of the Royal Meteorological Society. Also in 2008 she received an OBE for her outstanding contribution to climate science.

Google Earth as a plume tracker

For 3 weeks in January I was involved in more chemistry flights on the BAE 146 Atmospheric Research Aircraft. The flights were part of the NERC funded ROle of Nighttime chemistry in controlling the Oxidising Capacity of the atmOsphere, RONOCO, field campaign. The idea was to fly through pollution plumes in the hope that we could see some interesting chemistry going on. The mission scientists (that is the people in charge of where we go and what we do during the flight) use cloud forecasts from the Met. Office Mesoscale Model and air quality forecasts from the Met. Office Unified Model amongst other things to decide where is the best place to fly.

On 17th January it was decided that we would do a dawn flight and try to follow a pollution plume that was forecast to be coming from Glasgow and Edinburgh and flowing out over the sea from the Firth of Forth.

 

Example of the plots available to the mission scientist with aerosol forecast on the left and cloud cover forecast on the right.

Take-off was at 06:00 so scientists were allowed onto the aircraft from 01:00 to allow time for instruments to warm up and be calibrated. We took off from East Midlands Airport (EMA) on time and headed up to 10 000 ft to allow in flight calibrations to be done. Once these were complete we went back to EMA; this may seem like a strange thing to do but it makes sense. At night the lowest altitude we can fly at is 1500 ft so if we want to find out about the structure of the atmosphere below that we need to do what is called a 'missed approach'. This is where we pretend to land at an airport but when we reach 50 ft the pilot pulls up and we take off again. This allows us to get a full vertical profile of the atmosphere and much more information. 

So having got information about the structure of the atmosphere we headed up north to look for our pollution. Once over the sea we could descend to 1500 ft hopefully allowing us to get into the more polluted air closer to the surface. As we approached the area where the plume was predicted we started to see concentrations rising indicating that we were indeed seeing something. We flew north across the plume until concentrations seemed to drop again and then flew back and forwards through the plume offsetting slightly each time so that we were slowly heading further out away from the coast. From the measurements we thought that we were getting a nice picture of the plume but its hard to see when you're looking at the data against time rather than location. This is where Google Earth comes in; Axel Wellpot who works for the Facility for Airborne Atmospheric Measurements (FAAM) had done some clever computing which enabled us to see our data superimposed on a map....and not only that but we could also show the predicted aerosol as well to compare what was seen with the predictions. Have a look at the pretty picture below to see how good it is at showing where we saw the plume.

This shows nitrogen oxides in light blue with higher concentrations shown as taller peaks. The colours underneath are the predicted aerosol with yellow being highest and blue lowest. You can see that the plume was pretty much where it was predicted.

Google Earth could then be used to plan our route back towards the coast flying through the peaks in pollution. So from first impressions it looks like a successful flight in terms of finding and sampling a plume but also a brilliant use of available software allowing the in flight data to tell us the best place to fly next. This could be useful for BORTAS where we will have predictions of where carbon monoxide is highest and will want to try and find those places and fly in and out of the plumes when we locate them.

My First Research Flight

Sorry it's been so long, thesis writing and submission took over for a while. So I think it's time for an update...

On 7th of September I had my first flight on the UK BAe 146 Atmospheric Research Aircraft. This was my first opportunity to see the LIF instrument from L'Aquila (see post from Friday 11th June) in action since its installation on the aircraft. Piero and Eleonora (from University of L'Aquila in Italy) were already at the airport hotel and had been taking part in flights for the previous couple of weeks. It was decided when I arrived on the evening of the 6th that Eleonora and I would do the flight and so Piero would do the instrument warm up...for which we were very grateful. The flight was scheduled for take off at 04:30 and so pre-flight warm up began around midnight. Eleonora and I arrived at the aircraft around 02:30 for a final calibration and the security check and pre-flight briefing. A nice civilised hour for my first experience of science flying!

The plan for this flight was to watch the change in atmospheric composition as the sun rose and photochemistry began to breakdown species such as nitrate radicals and N2O5 and nitrogen oxide begins to be formed from photolysis of nitrogen dioxide. We took off from East Midlands Airport at 04:30 as planned and immediately ascended to 20,000 ft for our transit to the area of interest. Once we reached the designated point, just off the east coast near Middlesborough, we descended to 6000 ft and did a run up the coast to Aberdeen for the lidar to find the aerosol layers that indicate the presence of polluted air from the east coast. We then descended into the layers identified and did repeated runs through sunrise to see the transformation as photochemistry begins to occur. The LIF performed well with no obvious problems so fingers crossed the data will look good.

My second flight was two days later and at a more reasonable hour. This time we were aiming to find a suitably large ship and fly in and out of the associated pollutant plume. This gave the opportunity for some low level flying over the ship and I tried to get some pictures to show how close we were (see below).

This was the best picture I got as we flew over the ship whose plume we were attempting to sample.

I expected low level flying to be very turbulent but was a little disappointed that I didn't feel queasy at all and in fact the whole flight was surprisingly smooth (all credit to the brilliant pilots!). Again the LIF instrument operated with no apparent problems and we seemed to see large peaks as we transitioned through the ship's plume. So the changes made to the instrument to make it suitable for aircraft measurements do not appear to have significantly hampered the performance which is great news for the BORTAS campaign. Access to the lasers for changes in the alignment of the mirrors that direct the beams into the measurement cells is now only allowed when on the ground and whilst wearing laser goggles. Below is a picture taken between the two flights, it shows Piero and Eleonora trying to get the best sensitivity by making tiny changes to the alignment of the mirrors.

Having removed one panel Eleonora now has access to the mirrors inside the enclosure. Goggles must be worn by everyone on the aircraft since when the second panel is removed the green laser light can be clearly seen and could potentially damage eyes.

Paris and Plume Measurements

We’ve had a busy couple of weeks in Halifax, and now the BORTAS campaign for this year is in full swing. As well as the lidar we have a large array of other scientific measurement equipment set up here on the roof of the physics building at Dalhousie University, including a wind monitoring radar and instruments that measure particle sizes and ozone levels directly. I don’t have much to do with those instruments but we were all kept busy last week preparing and learning to operate the ‘Portable Atmospheric Research Interferometric Spectrometer for the Infrared’. PARIS, as she is known, is an instrument which measures atmospheric trace gases and should give us a better idea of what the chemical constituents of smoke plumes actually are. We also had to build a shelter for PARIS, a small shed that’s been named FRANCE. I’m not sure what that stands for, suggestions on a postcard, or by comment, please...

Portable Atmospheric Research Interferometric Spectrometer for the Infrared (PARIS-IR), operating on the roof of the physics building.

On the boreal biomass burning side of things: over the past week we’ve been getting a reasonably regular procession of biomass burning plumes passing overhead, as predicted by the GEOS-5 CO profile forecasts that Mark Parrington has been producing, and we’ve managed to measure the aerosols that we’d expected to be associated with that type of plume using the lidar. For example here’s the forecast and the lidar plot from measurements which took place on Wednesday and Thursday.

The CO from boreal biomass burning forecast profile over Halifax, showing high concentrations of CO at around 2km from 20 to 40 hours after the plot began (which was 1200 UTC on the 20th). This time corresponded to 0800 to 0400 UTC, and the lidar measurements from that time clearly show a similar shaped aerosol feature at roughly the same height and time. CO plot courtesy of Mark Parrington, University of Edinburgh.

You’ll notice that compared to the plot from the 9th July post, the aerosol layer here is much thicker, higher and more concentrated than the meagre one from that day. You’ll also notice how nicely it ties up with the CO forecast above. The smoke plume from a forest fire would be expected to carry high concentrations of carbon monoxide and high loads of aerosols, so it’s nice to see experimental data that seems to confirm this, and which also suggests that the CO forecasts are accurate.

We find out the locations of forest fires throughout North America from a number of sources. In particular Natural Resources Canada produce a daily plot showing where high concentrations of forest fires are occurring within Canada (http://cwfis.cfs.nrcan.gc.ca/en_CA/fm3maps/fwih), whilst FIRMS (Fire Information for Resource Management System, http://maps.geog.umd.edu/firms/kml.htm), of the University of Maryland, provide similar forest fire position plots for all of Northern North America as Google Earth files. Both services use satellite infrared measurements to find the fires.  As you will see from the plots below, we shouldn’t be running out of smoke plumes soon, we just hope that the wind brings them our way!

The Natural Resources Canada fire hotspots map for 22nd July , and the FIRMS google earth plot of fire locations during the 48 hours previous to the 22nd of July.

The google earth image above has been overlaid with a 72 hour Hysplit back trajectory matrix. The trajectories all end in a grid cantered on Halifax, with height and time relating to the aerosol layer discussed above. The trajectories seem to suggest that Halifax was at the focus of a region of converging air at that time, so the smoke plume could have come from anywhere in Northern and Western Canada, though it is tempting to assume that the fires visible to the west of Hudson Bay (which had also been burning for several days beforehand) were probably the source.

 Finally, if you take another look at the CO forecast plot above, you’ll notice an enormous concentration of CO due above Halifax around 60 hours after the plot began. Assuming the forecast is correct that plume should be overhead right about now, and that’s the reason why I’m sitting in the lab writing this blog at 02:30 on a Friday morning, hoping and waiting for the clouds to clear so that I can get the lidar fired up and start making some measurements!

Update from Dalhousie....

Post written by Eddy Barratt and Rob Trigwell

Well we’ve had a little practise and I (Eddy) had my first shift running the lidar solo on Monday night, though a combination of instant messaging, e-mails and phone calls meant that I had all the support that I needed. You might expect that the lidar can pretty much run itself, but there are still quite a lot of tasks that kept me busy. The most important of these is to do with aircraft safety.  We have a radar that shuts down the laser whenever an aircraft is in our vicinity. When this happens I have to go outside, look for the aircraft in question, then log it’s height and it’s direction before turning the laser back on. There are also helicopters that occasionally buzz over the city.  We have a microphone on the roof and we can hear them approaching from a fair distance, and we can shut off the lidar manually before the radar even detects them.

 The LIDAR running at night.

The data retrieval software also needs to be started every 60 minutes, and to produce the plots requires a little skill and patience. If you look carefully at the plot below (taken monday night, current plots can be found at http://aolab.phys.dal.ca/data/current/) you’ll see black bands at 5 and 5.5 km. These are where I’d set the normalisation limits. The software has to be told how much light to expect from clear, aerosol free air, and we do that by selecting a region and telling it that in that region the air is free of aerosols. Clearly if their are aerosols in that region the plots will look wrong, so selecting the right normalisation region is important. Usually you’d choose a region high up in the atmosphere but for that shift I was having to continually lower the region, to bring it under the cloud which had been steadily sinking all evening.

This plot demonstrates some interesting features. First, and most obviously, you can see the bottom edge of the cloud. It had fallen from about 9km at 2100 (GMT, 6pm local time) to 6km when I took the screenshot at 0230.. Occasionally, like between 2200 and 2300, the cloud was thin enough so that we were still getting some readings from above it, but for most of the evening the bottom of the cloud had been as far as our laser has reached. The second thing is the band of bright colours down low, in the first 700m or so. This is thin cloud or fog, it wasn’t thick enough to stop the beam, but it did provide enough reflections to show up quite significantly.

The third thing you might notice, with a keener eye, is the swirling blue tinted patterns between the two cloud layers. These are aerosols, which is exactly what we’re out here to look for. I’ll hand over to Rob who ran some further analysis, to try and find out where that aerosol came from...

Lidar profile above Halifax, and 5 days backward trajectory for air that was at 2000 m elevation at 2200 h on monday night, produced by the NOAA HYSPLIT model. Click on the figure to enlarge it.

Running the NOAA HYSPLIT model at the altitude at which the aerosols were being detected by lidar can give us an insight into source regions of these aerosols. The model uses what it knows about wind strengths and directions in the past few days to calculate what paths a given parcel of air has taken to be where it is now. As you can see from the plot, the back trajectories suggest that the aerosols could have originated somewhere in the US midwest, before making their way across Ontario and Quebec. These are not heavily industrialised regions so the aerosols are probably not anthropogenic. The actual source and type of these aerosols is a matter for further analysis. 

Back in Edinburgh, Mark Parrington is using forecast output from the NASA GEOS-5 system to predict the trajectories of biomass burning plumes, and when they pass over Halifax. The forecast CO profiles over Halifax (http://xweb.geos.ed.ac.uk/~mparring/BORTAS/Halifax/), plotted in a similar form to our lidar plots, highlight where Carbon Monoxide is strongly concentrated with the measured aerosol. CO is produced in a number of different processes, both industrial and natural, but in particular CO would be expected to coexist with aerosols from Biomass burning, so correlations between his plots and our own are very exciting.

CO forecast profiles over Halifax, plots courtesy of Mark Parrington, University of Edinburgh. Click to enlarge.

A last word from Eddy:

I should have mentioned in my last post that I’m here thanks to a grant awarded by the Nuffield Foundation, which I’m very grateful for, and very sorry not to acknowledge it last post.