PyroCb in the Irkutsk region of Siberia

COMS-1 0.675 µm visible channel images (click to play animation)

COMS-1 0.675 µm visible channel images (click to play animation)

The first unambiguous pyroCb event of the 2014 Northern Hemisphere wildfire season occurred in the Irkutsk region of Siberia, Russia on 18 May 2014. Korean COMS-1 satellite 0.675 µm visible channel images (above; click image to play animation; also available as an MP4 movie file) showed an increasing amount of smoke output from numerous fires burning northwest of Lake Baikal; toward the end of the day, a strong cold front moving eastward across the region appeared to be the catalyst for producing a pair of pyroCb events in the vicinity of Bratsk (station identifier UIBB).

A time series of surface weather for Bratsk (below) showed that smoke had been reducing surface visibility to 3-4 miles during the overnight and early morning hours, but the visibility then dropped to 1.9 miles as south-southeasterly winds began to increase ahead of the arrival of the cold front. Once the cold front passed, the surface air temperature dropped from 73ºF (22.8ºC) at 08 UTC to 43ºF (6.1ºC) at 13 UTC, as westerly winds gusted as high as 33 knots.

Bratsk (UIBB) time series of surface data

Bratsk (UIBB) time series of surface data

The  corresponding COMS-1 10.8 µm IR channel images (below; click image to play animation; also available as an MP4 movie file) indicated that for the second, more explosive pyroCb northeast of Bratsk the cloud-top IR brightness temperature crossed the -40ºC threshold at 10:45 UTC, and then became colder than -50ºC at 11:00 UTC (IR/visible image comparison). The coldest cloud-top IR brightness temperature was -57.8 at 13:15 UTC.

COMS-1 10.8 µm IR channel images (click to play animation)

COMS-1 10.8 µm IR channel images (click to play animation)

Looking at the 12 UTC rawinsonde data from Bratsk (below), the -57.8ºC cloud-top IR brightness temperature roughly corresponded to an altitude of 10.2-10.7 km.

Bratsk rawinsonde data ( 12 UTC on 18 May 2014)

Bratsk rawinsonde data ( 12 UTC on 18 May 2014)

Multi-angle Imaging SpectroRadiometer (MISR) smoke plume heights (below) confirmed that the maximum height of the smoke plume was in the 11-12 km range.

Multi-angle Imaging SpectroRadiometer (MISR) smoke plume heights

Multi-angle Imaging SpectroRadiometer (MISR) smoke plume heights

Using the NOAA ARL HYSPLIT model, forward airmass trajectories originating at the 2 pyroCb initiation sites near Bratsk (below) suggested an anticyclonic transport aloft over far northeastern Russia, eventually crossing over the Sea of Okhotsk.

NOAA ARL HYSPLIT forward airmass trajectories

NOAA ARL HYSPLIT forward airmass trajectories

The anticyclonic transport of smoke was confirmed by images of Suomi NPP OMPS Aerosol Index on 19 and 20 May (below; courtesy of Colin Seftor).

Suomi NPP OMPS Aerosol Index

Suomi NPP OMPS Aerosol Index

A similar anticyclonically-curved signal of smoke aloft was seen on the AIRS Carbon Monoxide mixing ratio product from 18 May (below).

AIRS Carbon Monoxide mixing ratio

AIRS Carbon Monoxide mixing ratio

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