Northern Ireland

Sahara dust to blame for 'dirty rain' in Northern Ireland

Sahara dust on a car Image copyright Firhouse, Dublin
Image caption The dust on cars has travelled all the way from the Sahara desert

Was your car dirty when you woke up on Sunday morning? Blame the Sahara!

The term Sahara dust refers to the sand and dust from the desert that can be transported northwards in the air when the wind is in a certain direction.

It results in a fine layer of dust being dropped when it rains - what we call dirty rain - and it can undo the cleaning of the car from the day before.

The predominant wind direction for Northern Ireland is west or south-westerly and most of Northern Ireland's weather comes from the Atlantic.

Image copyright @byebyethecheese
Image caption The view out to sea from the Long Hole in Bangor was very hazy at the weekend

This means that air is travelling over a clean, unpolluted surface.

When the weather turns colder and the winds are in the north, there is also a relatively clean air mass.

So, the wind direction is the key to not only determining where our weather is coming from, but also the state of the air that we breathe.

You may have noticed how hazy it has become recently when you look towards the sea from the east coast - this haze pollution is trapped within the south-easterly airflow.

You might think Africa is a long way from Northern Ireland but Saharan dust travelled from Africa all the way to the south of Florida - about 5,000 miles - in the summer of 2012.

Last summer, a massive Saharan dust cloud covered part of the Atlantic.

The wind direction will continue to be in the east or southeast over the next few days; so expect some more "dirty rain".

Image copyright ceciliadaly
Image caption The haze pollution is trapped within the airflow