Dense smoke over Argentina and Uruguay

By HansPeter Roesli (EUMETSAT)

The smoke plumes were driven by north-westerly winds (a rather unusual wind direction for the season).

By the second part of the week the smoke reached the estuary of the Rio de la Plata, blanketing Buenos Aires and prompting the authorities to close airports and major highways. Geomorphological details of the area of interest may be gleaned from an Aqua MODIS image (18 April, 17:50 UTC, source: NASA) and from a Meteosat-9 HRV image combined with Google Earth (KMZ).

The evolution of the smoke plumes can be followed very well on daytime SEVIRI imagery. Both the Natural Colour RGB (16 April 10:00 UTC–20 April 21:00 UTC) and, for more detail, the HRV channel (16 April 16:00 UTC–20 April 20:45 UTC) show the day-to-day changes. It should be noted that, over South America, the time coverage of the HRV channel is curtailed due to the configuration of the SEVIRI lower HRV window. The current configuration is as follows (see also example 24-hour HRV loop):

• Between 00:00 and 14:00 UTC the lower HRV window is east justified so as to optimise the coverage of the Indian Ocean region.
• Between 14:00 and 17:00 UTC the lower HRV window moves, every hour on the hour, incrementally westwards until in becomes west justified.
• Between 17:00 and 00:00 UTC the lower HRV window is west justified to optimise the coverage of the Atlantic Ocean and South America.

Although some light smoke plumes already reach the coastal areas beforehand, the really dense smoke started to flow into the Rio de la Plata estuary on 16 April (see HRV image, 19:30 UTC). On 17 April, the winds turned more westerly and drove the smoke out into the Atlantic (see HRV image, 19:30 UTC). A secondary plume moved towards the Montevideo area.

On 18 April, still driven by westerly winds, the smoke appeared to reach its largest extension, with a lot smoke also over the sea (see HRV image, 19:30 UTC). An enhanced image of MODIS channel 1 (18 Apr, 17:50 UTC) revealed wave structures of unknown origin. They appeared to be partially covered by the smoke and to be running roughly parallel to the coast.

On 19 April, cloud cover made the detection of smoke difficult, but the wind direction was unchanged with respect to the two days before (see HRV image, 19:30 UTC).

Finally, on 20 April, the wind changed veering to a more northerly direction (see HRV image, 19:30 UTC) and started to blow the smoke away from the mouth of the Rio de la Plata. The winds continued to blow from due north the next day (see HRV image, 19:30 UTC) freeing Buenos Aires and Montevideo of this unhealthy situation. However, fires continued to burn along the Rio Paraná as indicated by many individual smoke plumes on the HRV image and the hot spot area indicated in a Night Cloud Microphysics RGB (see 04:00 UTC image).

Additional content

Aqua MODIS True Colour RGB Composite with fire detection (21 April, JPG, source: NASA)