Update on Progress and Sources of Information

So the BAe146 ARA took off from Cranfield, UK yesterday and travelled down to Horta in the Azores where it stayed overnight. This morning it took off again to fly first to St John's and after a quick refuel, to Halifax, Nova Scotia. Early reports sent from Professor Ally Lewis who is mission scientist for the transit flight suggest that all instruments being operated on the transit are working well with a few minor issues at high altitude. Inflight data seemed to follow the predictions made by Mark Parrington's GEOS-5 CO forecasts remarkably well. The aircraft is due to land in Halifax around 1800Z or 1500 local time.

Andrew Elford uploaded a picture of the first ozonesonde launch for the BORTAS-B campaign to the BORTAS facebook group yesterday and it is also shown below. Hopefully we will have some other updates from the ground team soon as they have been working hard for the last few weeks getting everything running and collecting data in the run up to the aircraft campaign.

The first ozonesonde launch of the BORTAS-B campaign which took place at Egbert yesterday.

If you are interested in the data that is being collected there are a few online resources you might be interested in. Information about and data from the ozonesonde launches can be found at http://exp-studies.tor.ec.gc.ca/~bortas/. On this site there is a table containing the dates of launches and under each location links to a data file (labelled D) and a graph (labelled G) so that you can see what the vertical profile of temperature and ozone concentration look like. The Atmospheric Optics Laboratory at the University of Dalhousie has a webpage which links data from the Dalhousie ground station and has recent plots from the lidar, this can be found at http://aolab.phys.dal.ca/data/archive/halifax_2011/. They also have a page that will display live plots from the lidar at Dalhousie and that is located at http://aolab.phys.dal.ca/data/current/. If you want to see where the aircraft is when it is airborne this webpage http://faam.badc.rl.ac.uk/public/gluxe_position/satmap.html shows its current position and also the track it has taken during that particular flight. The GEOS-5 CO forecasts are updated daily at http://www.geos.ed.ac.uk/research/eochem/bortas/coforecast.html and the number of forest fires is displayed by the University of Maryland's web fire mapper at http://firefly.geog.umd.edu/firemap/. Of course you can also follow updates on twitter or facebook and keep visiting the blog for news, pictures and more information.

Comparison of GEOS-5 CO Forecasts with Satellite Measurements

At the science team meeting Mark Parrington from the University of Edinburgh presented an analysis of the GEOS-5 CO forecasts with satellite measurements during the BORTAS-A campaign last summer. His analysis showed that the predicted locations of elevated concentrations generally compared well with measurements but that the levels of CO were often overestimated.

On the left is the CO predicted by GEOS-5 using the IASI averaging kernels. On the right is the CO retrieved from the IASI satellite measurements.

It can be seen from the above plots that the levels of CO are overestimated by the GEOS-5 prediction relative to the IASI measurments and that the geographical spread of the elevated concentrations appears to be too great.  By plotting the difference between the modelled and measured data we can see more clearly that the model predicts too much CO in most ares (see plots below).

Plot showing the percentage difference between modelled and measured CO for satellite measurements reporting less than 12% cloud cover on the left and less than 5% on the right.

The percentage difference was plotted for measurements made when cloud cover was less than 12% and less than 5% to see if the lower values in the IASI CO measurements were due to cloud or aerosol in the pixels used for the calculation. The plots above show that the modelled values are still significantly higher when less cloud is present. The average bias towards higher values remains constant for different levels of cloud cover as the plot below demonstrates. This shows the probability distribution of the difference between the predicted and measured CO. The average difference is 10 % for both cloud conditions considered (less than 5% and less than 13%) and for all data and boreal only data.

This shows the probability distribution of the difference between the predicted and measured CO concentrations. The dotted lines show this just for the boreal region (> 50^oN) with the red lines showing data with less than 5% cloud cover and the black lines less than 13%.

So what we see is that the model seems to reproduce the locations where CO levels will be elevated but that it consistently shows a bias predicting much higher CO levels than those observed. This is not terrible news since our use of the forecasts is to enable us to be in the right place to observe the biomass burning plumes, characterised by high CO. It looks like the forecasts will be able to tell us where to go, just that we shouldn't expect to see concentrations that are quite as high as the model suggests.

Podcast Preparation

So this morning I had a meeting with Richard Hollingham, a journalist and broadcaster who presents the NERC Planet Earth Podcast. During the BORTAS campaign we will be recording an audio diary which, if my recording skills are up to it and my chat is interesting enough, will feature on the aforementioned podcast. There's a good example of the audio diaries they use in the podcast episode entitled "cuckoos at Wicken Fen, snow and radiocarbon dating". The audio diary starts around 9 minutes in.

There will be some challenges associated with recording on the plane, particularly the background noise. The aircraft cabin is pressurised so in theory it should be really quiet inside but with all the pumps that are used to draw air through the various instruments running the noise levels can actually be really high. We'll have to experiment with the best place to hold the microphone and what recording levels work best.

The audio recorder, cover and windjammer

So now I have in my possession a handheld digital audio recorder with microphone cover and windjammer, and I've been told to have a go at making recordings around the laboratory, outside and anywhere else with interesting noises. So those of you who work at University of York, beware, I might be after you for an interview....and anyone else involved in the campaign - practise being interesting so that we can get some brilliant interviews for the actual audio diary.

Ozone Sonde Launches

I have mentioned before on Twitter that we have some brilliant collaborations going on which will help us understand the data we collect during BORTAS this summer. Many of these have already started with scientists from a number of universities and institutes collecting data during the BORTAS-A period last year. In earlier posts I talked about the Pico Mountain Observatory and the lidar at Dalhousie University but another useful and exciting activity that will be going on this summer, and in fact goes on all year round, is the launching of ozone sondes across Canada by the Environment Canada Experimental Studies Unit (ARQX).

The first question might be 'what is an ozone sonde?'....good question. Sonde is the French word for probe and so it makes sense that this is essentially a probe to measure ozone. They are lightweight instruments that can be carried by a helium filled balloon (not a party balloon, these ones are slightly bigger and more robust). The iodide redox reaction (shown below) is used to allow ozone to be detected.

2KI + O3 + H2O -> I2 + O2 + 2KOH

This reaction is used to produce an electrical signal which is proportional to the ozone concentration. This can be done in a number of ways each of which is explained at http://www.atmosp.physics.utoronto.ca/SPARC/SPARCReport1/1.08_O3sondes/1.08_O3sondes.html. The sonde also includes meteorological instruments to measure pressure, temperature and humidity. The balloon carrying the ozone sonde can travel upwards as far as 35 km before the balloon bursts. This happens because as pressure decreases higher up in the atmosphere the helium inside the balloon expands into the lower pressure surroundings. The balloon can not expand indefinitely and so eventually it bursts.

 On the left is the inside of an ozone sonde showing the two solutions used to create the electric current. The other two pictures show ozone sonde launches with the middle one using a special balloon which can get to higher altitudes (it looks very dramatic!).

ARQX launch ozone sondes weekly from ten locations across Canada. During BORTAS they will also launch daily sondes from Yarmouth, Sable Island, Goose Bay, Egbert and Bratt's Lake. There is also the possibility of additional launches if a plume is predicted to pass over one of the launch sites. The sites are all shown on the map below. Ozone sonde launch sites are identified by the symbol that resembles a balloon carrying an object (an ozone sonde of course). Also depicted on this map are sites that operate lidar instruments similar to that operated at Dalhousie University and sites which have Brewer spectrophotometers. These instruments measure total ozone and UV radiation, to find out more have a look at the Environment Canada pages at http://exp-studies.tor.ec.gc.ca/e/ozone/ozone.htm.

Network of ozone sonde launch sites, lidar locations and sites with Brewer spectrophotometers.

David Tarasick from ARQX kindly provided me with some plots from data collected during the BORTAS-A period last year. On numerous occasions the vertical profiles from ozone sonde flights show regions of elevated ozone. An example of this is shown below.

Left hand plot shows the vertical profiles taken by the ozone sonde at Edmonton with ozone mixing ratio in black. The area of high ozone is circled in red. The right hand plot shows where the air at Edmonton had come from overlayed on the fire counts for the previous day.

These plots show that the air sampled is likely to have been impacted by the fires north east of Edmonton and this could be the cause of the elevated ozone. Another example is shown below from the Goose Bay site. This shows not only the data from the ozone sonde but also aerosol measurements from the lidar and the carbon monoxide (CO) forecast carried out by scientists at Edinburgh University. All plots indicate something is happening between 4 and 8 km with CO and ozone mixing ratios and aerosol backscatter ratio and cross section all being elevated.This supports the suggestion that the elevated ozone is a result of biomass burning activity. 

The top left plot shows the ozone sonde profiles, top right is the predicted CO from the GEOS-5 model, bottom left is the aerosol backscatter cross section and bottom right is the aerosol backscatter ratio.

From this data we can say that elevated ozone is observed at ozone sonde stations downwind of large boreal forest fires. Back trajectories suggest that the sampled air passed over a region of burning. This elevated ozone may be the result of reactions involving nitrogen oxides, CO and hydrocarbons which are present in biomass burning plumes. The presence of aerosol layers at similar altitudes would support the suggestion that burning plumes have influenced the composition of the air mass. A possibility that can not yet be ruled out is that the elevated ozone is from air that has travelled into the lower atmosphere from the stratosphere where ozone concentrations are significantly higher. This is supported by the relative humidity profiles which show dry air at the altitudes where ozone is elevated but the coincidence of plume interception (suggested by the lidar aerosol data and trajectories) and downwards mixing of stratospheric air is unexplained. Hopefully measurements this summer will add some pieces to this puzzle and help us understand the processes going on in and around aging forest fire plumes.

Thanks to David Tarasick for pictures, data plots and information.

Satellite Measurements of Trace Species

Post written by Keith Tereszchuk.

One of the objectives of BORTAS will be to compare the in-situ aircraft measurements made during the flight campaign with remote sensing data provided by satellites. Space-borne observation is used extensively in many facets of monitoring of the Earth’s surface and atmosphere including weather forecasting, air quality measurements, ozone levels (UV Index), volcano emissions, ocean currents, sea/lake roughness (wave height), desertification assessment and numerous other such environmental management studies.  These are just a few examples of the importance of satellite monitoring and how the information they provide us directly impacts our day-to-day lives. The identification and characterization of biomass burning plumes and their effect on atmospheric chemistry is yet another area of study conducted using satellite remote sensing.

 

SCISAT-1 with ACE-FTS

BORTAS will be using data from the Atmospheric Chemistry Experiment (ACE) on-board the Canadian satellite SCISAT-1, which uses a high-resolution Fourier transform spectrometer (ACE-FTS) for remote sensing of the limb (see picture) of the Earth's atmosphere down to 3-km above the Earth’s surface (just above the tropospheric boundary layer). The ACE-FTS has wide spectral coverage in the infrared region of the electromagnetic spectrum scanning a contiguous region from 750 to 4400 cm-1 and currently offers data retrievals for 38 molecular species as well as their isotopologues, over a dozen of which are known biomass burning marker species, e.g. CO, HCN, HCOOH, H2CO, C2H6, C2H2, CH3OH, HNO3, CH4.

 

View of the limb of the Earth at sunset

Unlike nadir instruments, which look directly down towards the surface of the Earth, ACE peers through the limb of the atmosphere recording sequential absorption spectra using the sun as an emission source. Each sunrise and sunset of the satellite is called an occultation and they provide concentration profile information of each molecular species with respect to altitude.  Much like ogres and onions, ACE can be used to separate the atmosphere into distinct layers with a spatial resolution of 1 km. On average, 20 measurements are made on a daily basis.

 

The Atmosphere: It has layers

 

ACE occultation of the Earth’s Atmosphere

               ACE provides widespread global coverage and during the BORTAS campaign, it will make a total of five measurements that will be within the 500 nautical mile range of the FAAM aircraft which will be based in Halifax.  These measurements will be used to compliment the data recorded during the aircraft flights to further understand the chemical evolution of molecular species emitted by biomass burning. 

Positions of the predicted ACE occultations, shown by circular ACE logos. The red circles show the distance from Halifax where the aircraft will be based.

              Ideally we would like to be able to identify the sources of the plumes that will be measured during the campaign to study molecular evolution within them, and satellites can help us do that too. We will be using data from the MODIS Terra instrument, which is a spectroradiometer that records surface temperatures of the Earth including thermal anomalies such as actively burning fires, to identify potential source regions. When the location of fires are known, we can determine the plume sources by calculating air-mass trajectories using a program called HYSPLIT, which is a Lagrangian particle dispersion/trajectory model based on satellite climatologies. These climatologies provide information on air-mass flow at a particular time at any point in the atmosphere across the entire globe.  Using the ACE profiles of the biomass burning marker species, we can determine the altitude that corresponds to the highest concentrations of these molecules and use this altitude as the injection point for backtracking the air-mass flow to its source using HYSPLIT. In addition, we can calculate forward trajectories from identified sources. If these trajectories coincide both spatially and temporally, we can confidently confirm the source of the plume measured.

 

HYSPLIT trajectories. Backtracking from an ACE measurement made over Hudson Bay and four forward trajectories made from known biomass burning events over northern Saskatchewan and the Northwest Territories (July 2008).

              Bringing together all the aforementioned information, we will be able to characterize biomass burning plumes to further our understanding of the overall impact of biomass burning on atmospheric chemistry.