Satellite image of the month

February 2020 - Saharan dust blankets Canary Islands

22 February 2020

On the 22 and 23rd February strong winds over western Africa lifted dust from the Sahara desert and advected it over the Canary Islands. This image, captured early in the dust event, shows the dust streaming from Africa over Lanzarote and Tenerife. The islands further west were affected later. In a meteorological phenomenon known locally on the Islands as “Calima", dust was carried by gale force winds which severely reduced visibility on the islands. There were extensive impacts including closure of most airports on the islands with hundreds of flights affected. People were advised to stay indoors, events were cancelled and schools did not open until Tuesday. While a Calmia is not uncommon, local sources claimed this event was the worst seen in the last 40 years.

As the dust was low in the atmosphere it interacted with the land-masses of the Canary Islands producing ripples in the wake of the islands which can be seen in this true-colour image from NASA's Terra satellite. Further ripples can be seen in the dust where it passes from the African coastline over the ocean.

Credits:  Image: NASA Worldview

January 2020 - Polar Low system near Scotland

28 January 2020

A Polar Low is a small and short-lived weather system associated with severe weather including high winds and snow. They can form when cold polar air moves over the relatively warmer sea, triggering convection. The rising air leads to the development of cumulus and cumulonimbus clouds. In the right conditions these clouds wrap into a tight circulation around a rapidly deepening low pressure centre. Due to their intense winds they can cause problem to mariners, but normally dissipate quickly over land.

On 28th January a Polar Low with a cyclonic spiralling cloud and a marked eye could be seen in satellite imagery over the Atlantic ocean to the north east of Scotland. This true colour image from 13:37 UTC was produced using data from the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi/NPP, a NOAA/NASA operated polar orbiting satellite.

Credits:  Image: © Crown copyright, Met Office, Data: NOAA/NASA

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