The previous blog about UV pointed out we’d be lucky to get data for a few days given a desert crossing seemed to be imminent. So it was a surprise to receive an email last night – had he gone back to the Langue de Barbarie?? – and even more surprising to see where he was when the incomplete data downloaded.
Paul’s weather analysis offers a possible explanation for the sudden change. Over to him.
“When the e-mail from UV’s tracker came in, it was very late on Tuesday and – as Joanna has already mentioned – a whole 36-hour period was missing. At first it was not clear why UV had chosen this odd-looking path, or why he seemed to be moving south into Mali on Tuesday afternoon, when we expected him to be heading NORTH!
The first clue came from an earlier Ornithondar blog entry by our old friend Frédéric Bacuez, who mentioned the ‘harmattan’ (the hot sand-laden NE wind that blows out of the western desert.) A check of sandstorm monitoring images from the SEVIRI satellite instruments shows a lot of convection activity in the region. We don’t get this data in real-time – it is about two days in arrears – but it suggests that UV found his route northwards being obscured by dust and the resultant poor visibility. Until the missing tracker data has “filled in”, we won’t know for sure at what point he turned back, but it is now clear that he did so. This graphic shows UV’s track in green, overlaid on the SEVIRI infra-red spectrograph pictures from Monday afternoon.”
On his journey SE from late morning on 25 April UV followed the line of the eastern escarpment of a geological depression, Erg Aoukar. He roosted on one of the cliffs.
The minute by minute fixes show him catching some thermals as he flew. He set off in the same direction on 26 April and crossed the border into Mali at 14.30.
He was heading for a greener area, the NW edge of the Inner Niger Delta. He roosted west of a large town, Niono, near which there are sugar cane plantations.
Today he set off in a NE direction and by lunchtime he was nearing Lake Debo on the NE edge of the Delta. Would he stop and consider his options over a fish? After all he has flown well over 1500 km since Saturday. No – he did drop altitude to under 400m but sped over and onward. He has been moving at over 100 kph on some fixes today.
Here is a context map.
Paul has written an informative article about crossing the desert, well worth a read whatever UV does next!