Met-8 Natural Colour RGB

Impact of California 2020 fires on atmospheric composition

15 August-22 September 2020

Met-8 Natural Colour RGB
Met-8 Natural Colour RGB

Data from multiple satellites and instruments can be used to investigate the impact the extensive California fires that ravaged the US state in 2020 had on atmospheric composition.

Last Updated

06 May 2022

Published on

02 December 2020

By Federico Fierli (EUMETSAT) and Ivan Smiljanic (CGI)

Each year we observe extensive and prolonged wildfires in many regions — the US state of California is known to be one of the most regularly affected. However, 2020 appears to be exceptional with preliminary data and estimates showing record-breaking extent and fire emissions. The first week in September 2020 was characterised by an even higher intensity of such phenomenon, as documented by satellite observations.

This case uses a series of different measurement techniques, to highlight some key elements of the wildfires during summer 2020 in California. The season was particularly intense in terms of burnt areas and intensity of fires, with intense trans-continental transport of smoke and pollutants. In addition, NASA reported that from 6 September there was an unusual pyrocumulonibus (Piro Cb) in southern California. Such clouds, that develop relatively often during intense wildfires at high latitudes, are much less frequent in temperate regions. They are comparable to convective towers and are generated by fire at high temperatures. A key feature of these clouds is to project at higher altitudes the fire-emitted materials, such as gas and particles, thanks to the intense uplift amplifying the impact of the fire on the composition of the atmosphere.

Pyro-convection

This same cloud is shown in the Metop-C infrared image (Figure 1) as a white corona-like structure (the high cloud) with a plume extending out of it (the particle outflow). Vertical uplift has a role in spreading fire emission products much further distances. Horizontal transport is more efficient at higher altitudes in the atmosphere due to stronger winds and less efficient removal. The cloud is also observed as a composite 'RGB', especially for Dust RGB contrast. It exhibits unusual green and yellow shades — possibly linked to stronger vertical ash ejections of ash and SO2 gas. (Figure 2).

Metop-C infrared
Figure 1: Metop-C infrared (10.9 um) 7 September 7th, 01:12 UTC. The image is centered over California.
Figure 2: GOES-17 ABI Dust RGB capturing Piro Cb plumes on 6 September 2020, hourly loop from 00:30 to 23:30 UTC.

Active fires

Widespread fires can be easily detected with the Fire Temperature RGB (Figure 3). This RGB shows information on the intensity of the fires, utilising respective temperature sensitivity of the following channels: IR3.9, NIR2.2 and NIR1.6. However, this RGB product is 'blind' to thinner clouds that might mask the fires, i.e. dampening the perceived intensity of the fire. Also, during the night it only shows the fires, with no situational awareness about the clouds and other features in the atmosphere or on the ground.

In attempt to tackle these two pitfalls, similar options for the 'Fire Temperature' RGB were explored (Note: names are only working titles for these RGBs).

GOES-17 Fire Temperature RGB image comparison

GOES-17 ABI Fire Temperature RGB during the night compare1
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Figure 3: GOES-17 ABI Fire Temperature RGB during day and night fire scene on 9 September 2020, at 09:00 and 21:00 UTC.

GOES-17 ABI 'Fire RGB' image comparison

GOES-17 ABI 'Fire RGB' during the night compare1
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Figure 4: GOES-17 ABI 'Fire RGB' (IR3.9, NIR2.2, NIR1.3) during day and night fire scene on 9 September 2020, at 09:00 and 21:00 UTC.

GOES-17 ABI '24h Fire RGB' image comparison

GOES-17 ABI '24h Fire RGB' during the night compare1
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Figure 5: GOES-17 ABI '24h Fire RGB' (IR3.9, IR10.4, BTD12.3-10.4) during day and night fire scene on 9 September 2020, at 09:00 and 21:00 UTC.