Natalie Ratcliffe – email@example.com
My PhD project was could have been done entirely from behind a computer screen, but I ended up in Cape Verde for 3 weeks in June 2022 on a field campaign.
Working with Dr Franco Marenco from The Cyprus Institute (CyI) and my supervisor at Reading, Dr Claire Ryder, I managed to get some funding to spend 3 weeks in Cape Verde alongside an organised campaign. The ASKOS campaign was created to calibrate and validate aerosol, wind and cloud products from the Aeolus satellite, launched in 2018. They planned on using a combination of ground-based instruments and drones supplied by the Unmanned Systems Research Laboratory (USRL) with CyI to profile dust above Cape Verde to compare with the Aeolus aerosol products.
My PhD project is based around trying to understand how some large dust particles (diameter > 20 um) are travelling much further from the Sahara than expected based on their deposition velocity. One theory about how these particles are transported so far is that they are vertically mixed throughout the depth of the Saharan Air Layer (SAL, dry dusty air layer transported from the Sahara, typically up to ~6 km altitude) during convective mixing in the daytime. At night, with the removal of this convection, these large particles begin to settle through the SAL at a faster rate than other fine particles, before being mixed up again to the top of the SAL during the convective day. This is hypothesised to increase the time taken for the particles to reach the surface, encouraging long-range transport of these coarse particles. We proposed to fly drones with optical particle counters attached up through the SAL during the day and night to see if this theory has any standing.
Before I could go to Cape Verde came all the admin and preamble for going on a field campaign. Before booking flights and accommodation, the wonderfully long health and safety risk assessment form must be completed and approved. Reading through that form really makes it feel like you’re going to face every single threat known to humankind while you’re off campus; hurricanes, volcanoes, Covid-19, getting bitten by ticks (other animals/insects are available), sunburn (to be fair, a very real concern for me) and even getting hacked and bribed. I suppose being prepared for all these eventualities is meant to make it less scary
I had three virtual meetings with everyone involved in the campaign before we travelled, so I had a little bit of an idea what I was supposed to be doing when we were out there. Though to be honest, I still wasn’t entirely sure until a couple of weeks before we left! Claire and I had to introduce our work and what we wanted to achieve from this campaign. I was a little apprehensive as we were going to be requesting to collect data in the very early morning (3-6am ish) meaning we’d have to ask some of the other scientists to be up very early (or late depending on your opinion).
Now we get to the fun part where I actually go on the campaign (or on holiday as some people kept insisting. FYI, this was absolutely not the case). Most days would start with a few of us looking at the forecast to work out when we should aim to fly the drones. We would decide on a plan for the day, a suggested plan for the next day, briefly looking at data from the day before and then collating this all into a newsletter which was sent out to everyone on the campaign. These forecasts were useful for those collecting in-situ observations as well as those working on the ground-based remote sensing equipment. It also became very clear in these meetings that each scientist had a preferred forecasting model. We had so many options for forecasts (SKIRON, Met Office, CAMS, IAASARS, ECMWF etc), as well as varying satellite retrievals (EUMETSAT Dust RGB, MODIS NASA AOD, NOAA GOES-East visible images etc) and near-real-time observations from the ground instruments (PollyXT LIDAR, HALO Doppler wind lidar, CIMEL Sunphotometer etc) that there was occasionally some jostling to work out which forecast and measurements to trust and focus our planning based on! I was then able to go to the airport to help the flight team. I would refer to the most recent reading from the lidar and suggest which layers in the dust should be sampled with filters, as well as checking the wind lidar to make sure it wasn’t getting windier.
Looking back, we should have focused our forecasting on the wind and cloud more than the dust concentration. Initially, we were planning to measure when there was an interesting or high concentration dust event over the island. However, we eventually realised that the wind and cloud cover were the most limiting factors for measuring in terms of the in-situ and ground-based measurements, respectively. This unfortunately meant that, on a few occasions, the flight team were stuck at the airport waiting for the winds to drop before they could launch the drones. Or that the remote sensing teams couldn’t take results at the same time as the drones because there was too much cloud. It was a learning experience for everyone involved!
I’ve taken away four things from this campaign that it seems will probably happen on any field campaign, so take note if you ever get the opportunity!
- You’ll get to meet some really cool people
- Probably get food poisoning
- Your equipment will break at some point
- And many things will go wrong… It’s an inevitability
Some of the issues we faced were: instruments taking longer to calibrate and setup than expected, helium arriving two weeks late, missing weather balloons, two got covid, five got food poisoning, one drone crash-landed, too windy to fly the drones, not dusty enough, too cloudy for the lidars… It was definitely an exercise in contingency planning. I did say that this was a fun experience and I do mean it! Though there were many tense moments where things went completely opposite to the plan, I got to meet a lot of cool scientists, learn about new instruments, go to Africa for the first time and get hands on with some dust at last!
Feel free to check out this blog post which I wrote for ESA’s Campaign Earth blog page: (https://blogs.esa.int/campaignearth/2022/08/03/delving-deep-into-dusty-skies-on-the-askos-aeolus-field-campaign/).
This blog article is part of the DAZSAL project that is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRAIA-2020-1, Grant Agreement number: 101008004, Transnational Access by ATMO-ACCESS.