Hot spots and smoke from a deadly, widespread forest fire in central Portugal could be seen by Meteosat, Sentinel-3 and Suomi-NPP on 18, 19 & 20 June 2017
21 February 2023
18 June 2017
By HansPeter Roesli, Dan Lindsey (NOAA), William Straka III (CIMSS ) and Jochen Kerkmann and Vesa Nietosvaara (EUMETSAT)
At least 62 people died and dozens more were injured when wildfires raged across the central region over the weekend of 17/18 June. It was reported in the Guardian on 19 June that more than 1,500 firefighters were still battling to control the fires.
The Meteosat-10 Natural Colour and infrared animation, 18 June 06:00–19:00 UTC shows the outbreak and evolution of disastrous wild fires south of the city of Coimbra in Portugal. It is possible the fires were ignited by thunderstorms, the remnants of which can be seen north of Coimbra at the beginning of the animation.
The images are a combination of visible imagery (background image is the Natural Colour RGB) and IR3.9 imagery (overlaid for hot spot areas with brightness temperatures > 325K), both from Meteosat-10.
On Figure 1 the yellow arrows points to spots hotter than 325K from the IR3.9. The dark arrow points to an already burnt area and the light-blue arrow points of faint smoke, both shown by the Natural Colour RGB.
The hot spots and smoke spread and intensified in the early afternoon, but also got partially covered by convective cloud.
A series of hot spots can also be clearly seen on the animated gif of the Meteosat-10 infrared 3.9 micron band, 18 June 03:00–14:45 UTC (Figure 2).
The smoke from the fires is well seen both Sentinel and Meteosat, on the 18 and 19 June. It appears as haze on the Sentinel-3 OLCI Tristimulus RGB (Figure 3) and as a cyan-coloured plume over the Bay of Biscay, north of Portugal, on the Natural Colour RGB (Figure 4).
Over the following days the huge smoke plume from these fires moved over the Atlantic and reached the English Channel (western France and South West England).
NASA's Suomi-NPP passed over Portugal at 02:04 UTC (03:04 local time) on Sunday morning, roughly three hours after a mass evacuation. The VIIRS instrument on the satellite captured imagery of the fires.
Looking at the Day Night Band (Figure 5) it is easy to mistake the fires as a bright city with cloud surrounding it, however, the true story can be found in the IR channels. The fires were so intense that the I04 (3.95µm) band saturated out at 367K, something not normally seen in wildfires.
Additionally, the fires could clearly be seen in the I05 (11µm) channel with a recorded a brightness temperature (BT) of around 300K. The M13 (4.05µm) channel, which is a dual gain channel used for fire detection, had a maximum brightness temperature of 554.8K. For reference, the saturation BT of Band 7 (3.9µm) ABI is around 411K. It's estimated that the biggest blaze was around 15 km wide, with hot spots covering a width of around 27km.
Wildfires Light Up Portugal (NASA Earth Observatory)
Portugal wildfires – in pictures (The Guardian)
Ash from Portugal (MeteoSwiss, in Italian)