Hole in the Fog: an extraordinary visualization of UHI

Says Wikipedia

An urban heat island (UHI) is a metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The phenomenon was first investigated and described by Luke Howard in the 1810s, although he was not the one to name the phenomenon. The temperature difference usually is larger at night than during the day, and is most apparent when winds are weak. UHI is most noticeable during the summer and winter.

Does UHI have a large role to play in global warming? Maybe. Maybe not. But it surely has a very visible impact in the Po Valley in Italy.

This is a Eumetsat picture from sometimes on Dec 8, 2013. Can you spot where the city of Milan is?

Po Valley, Italy, Dec 8 2013

Of course you can. It’s the hole in the fog. With just 8 million people and a GDP of $150 billion (not far from New Zealand’s) Milan wouldn’t affect its weather, would it? /sarc

As a rough guide to the areas involved, Milan covers 70 sq mi, and the fog on that day around half of the Po Valley‘s 17,760 sq mi (4 parts in 1000).

(H/T Meteogiornale where the original news appears)