Today is my last day at the site, and I’m heading home tomorrow. The formaldehyde instrument is still running – Trev and Danny will pack that away on Monday. I’ve packed everything apart from the bare bones of the glyoxal instrument, which we have yet to move out of the lab (a very tight fit through the doors) and into the flight case ready to be shipped back to the UK.
The fieldwork has been a real success, with near-continuous measurements of glyoxal for both 4-week campaigns, and some promising measurements of formaldehyde during the second campaign. I’m pleased it’s gone so well, and I’m looking forward to getting back. We’re very grateful for the huge amount of help we’ve received from our colleagues in York and here in Cape Verde.
I think that’s all for now though I will try to post updates about the data analysis as we go along – thanks for reading!
Blazing sunshine, 27 degrees, and 92 % humidity…. what a day to start packing up!
We’re slowly winding down towards the end of the campaign now, so the task of packing the flight cases with equipment and stacking them in the shipping container has begun. It’s pretty sticky work!
The instruments will keep running until the last minute, and will be the last items to get packed away.
We woke up this morning to a hot and sunny Mindelo – no sign of yesterday’s rain. We popped to the site to check everything was still working (it was) and then set off on a bit of adventuring. Our plan was to see if we could get up to the volcano crater beyond Calhau. We have a map of Sao Vicente but it’s somewhat vague, so we ended up on a grand tour of the south east corner of the island, looking for the right track to get us close to the crater.
The first track we chose took past the volcano but the route up that side didn’t look very inviting (long, steep and rubbly), so we kept going to see where the track went. It took us into what felt like desert, where we got great views of some mountains (Pico do Vento and Topona), and spotted two osprey. The track ended right at the coast, at a place called Praia de Palma Carga where there’s a sandy beach, some rocky coastline, and more views of the mountains.
We had a look at the map and spotted a track that should lead us round the other side of the volcano, so we drove back the way we had come and kept an eye out for it. By the time we had nearly reached the main road we concluded that the track is either very well hidden or it doesn’t exist.
We had one more track to try, which took us past some farms and small buildings. It was both rougher and sandier than the track to Praia de Palma Carga, but I was reasonably confident the Jimny could handle it so we pressed on. The area near the road started to become familiar, and I realised I had walked up towards this track from Calhau during the last campaign. I had been aiming for the volcano crater but the heat and the rocky, sandy terrain got the better of me. Not so this time! We parked up and had a short but very hot walk up a path up the side of the volcano.
I wasn’t expecting the crater to be so big! A loose path took us down over the edge into the crater, where numerous people have gone to some effort to arrange boulders to spell out their initials and the date they visited. There is more vegetation inside the crater than outside, and goats clearly graze there from time to time.
Since we were feeling adventurous, we climbed out of the other side, and headed back round the rocky edge of the crater to the path we had taken up the side. From there it was an easy walk back to the car, and we were back in Mindelo in time for lunch.
It’s been a cloudy, gloomy, blustery day, with a big swell on the sea, drizzle this morning, and a slightly heavier shower this evening. Perhaps the annual rain will arrive this weekend!
We’re half-way through the campaign now. So far it’s not been as smooth as the previous campaign, but we’re hoping for a better second half! We will try (yet again) to calibrate the formaldehyde instrument this afternoon, and hopefully I’ll have some more interesting posts to add in the near future.
I haven’t got any science-y photos today, but I do have some of the cheeky visitors we get occasionally at the site, and each morning at the apartment.
New instruments (like our formaldehyde instrument) often only reveal their true colours when you get them in the field, creating problems which laboratory conditions don’t cause. Our aim is to fix what we can while we’re here, work out what we need to do back in the lab, and learn how to improve the instrument.
We’ve been looking at various signals (such as the frequency and stability of the laser pulse) on the oscilloscope (pictured above), which is a very handy way of visualising what’s going on in terms of signal processing inside the instrument.
One of the problems with the formaldehyde instrument – a poor connection between the laser and the timing control system – was difficult to diagnose but easy to fix, and measurements are underway once again.
We spent an hour or so today sorting out the detector pressure for the glyoxal instrument. It was previously controlled with a fiddly valve which needed adjusting now and then, requiring some crawling around under the instrument. It has now been replaced with a very short section of thin tubing, cut to exactly the right length to give the required pressure in the cell – about 90 Torr (about 0.1 bar).
After a lot of work Steve is now happy with his GC measurements of terpenes and halocarbons, and is going to run his first ambient sample this evening.
We’re having some trouble with the software for the formaldehyde instrument, so we had to abandon the calibration for the time being, and we’ve decided to stop the measurements for a short while. We hope to be able to fix it quickly, but these sort of problems are usually best solved after a bit of a break so we’re going to leave it switched off overnight.