Lombok waves visible from space
Lombok Strait, between Bali and Lombok, experiences some of the strongest tidal flows on earth, a result of it being one of the main Indonesian throughflows between the Indian Ocean and Pacific Ocean.
Water transport through the Strait is seasonal, affected by the difference in atmospheric pressure across the ocean basins, which is driven by the monsoon.
During the south-east monsoon (our winter), sea levels are lower on the Indonesian side and the flow is from north to south. This reverses during the north-west (summer) moonsoon, but the average flow is to the south.
Amplifying the currents through the Strait and between Lombok and Nusa Penida is an underwater sill sitting at a relatively shallow 200m, with the ocean plummeting down to 4000m to the south, while to the north ocean depths drop to 1000m.
Being one of the only access points between the Indian and Pacific Oceans the ocean dynamics and currents through Lombok Strait are some of the most complex and fastest in the world.
Ocean transport rates of between 2-4,000,000 cubic metres per second - yes, per second! - are recorded through Lombok Strait, and this along with the extreme water depths have helped prevent animal species crossing between Asia and Australia. This fauna boundary is known as The Wallace Line and runs right through Lombok Strait, east of Borneo and south of the Phillipines.
With varying water densities and current speeds between the surface water and water flowing over the sill, large internal distrubances (waves) are created which are visible from space. This is relatable to disturbances seen when water floods or spills over a weir.
These internal waves travel both north and south of Lombok Strait depending on the throughflow direction with reports of them breaking and capping at times from people making the crossing to Lombok from Bali.
A satellite image taken at the start of November reveals these internal waves propagating north from Lombok Strait, visible due to sunglint: a phenomena where the ocean is so still and glassy that sun reflects off it, straight back at the observing satellite making it almost mirror like.
This has helped identify the strong internal waves which can have wavelengths up to several kilometres.