Wildfire smoke: from Alaska to Norway, via the Arctic and Atlantic Oceans

July 18th, 2015

Meteosat-10 0.8 µm visible channel images [click to play animation]

Meteosat-10 0.8 µm visible channel images [click to play animation]

EUMETSAT Meteosat-10 High Resolution Visible (0.8 µm) images (above; click to play animation; also available as an MP4 movie file) revealed the hazy signature of what appeared to be a ribbon of smoke aloft being transported eastward across the North Atlantic Ocean by the circulation of a large area of low pressure (surface | 500 hPa) on 17 July 2015. Early in the day, the smoke feature stretched from the east coast of Greenland to the central Atlantic Ocean; by the end of the day, the leading edge of the smoke had moved over the British Isles and was headed toward Scandinavia.

A portion of the smoke plume could be seen on Aqua MODIS and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images (below) as it was approaching the southern portion of Great Britain.

Aqua MODIS and Suomi NPP VIIRS true-color images [click to enlarge]

Aqua MODIS and Suomi NPP VIIRS true-color images [click to enlarge]

On the following morning, Meteosat-10 visible images (below; click to play animation) showed that the leading edge of the smoke ribbon was moving over southern Norway.

Meteosat-10 0.8 µm visible channel images [click to play animation]

Meteosat-10 0.8 µm visible channel images [click to play animation]

The transport pathway of this smoke feature was rather interesting, as we shall explore with the following sets of images.

Suomi NPP VIIIRS 3.74 µm shortwave IR and 0.64 µm visible images on 06 July [click to enlarge]

Suomi NPP VIIIRS 3.74 µm shortwave IR and 0.64 µm visible images on 06 July [click to enlarge]

The 2015 wildfire season in Alaska had been very active — as of 17 July, it was rated as the 4th worst in terms of total acreage burned. In early July, numerous wildfires burning across the interior of Alaska were producing a large amount of smoke, as can be seen in a comparison of of Suomi NPP VIIRS 3.74 µm shortwave IR and 0.64 µm visible channel images at 2131 and 2312 UTC on 06 July (above). The thermal signature of the wildfire “hot spots” showed up as yellow to red to black pixels on the 2 shortwave IR images, while the widespread smoke plumes from the fires are evident on the 2 visible images; even in the relatively short 101 minutes separating the two sets of VIIRS images, notable changes in fire activity could be seen.

Looking a bit farther to the north and west, a sequence of VIIRS 0.64 µm visible images centered over Cape Lisburne (station identifier PALU) in northwestern Alaska covering a 2-day period from 06 to 08 July (below) showed the initial transport of large amounts of smoke from the interior of Alaska northwestward over the Chukchi Sea between Alaska and Russia.

Suomi NPP VIIRS 0.64 µm visible channel images covering the 06-08 July period [click to enlarge]

Suomi NPP VIIRS 0.64 µm visible channel images covering the 06-08 July period [click to enlarge]

Daily composites of Suomi NPP OMPS Aerosol Index covering the period of 04-17 July (below; courtesy of Colin Seftor; see his OMPS Blog post) showed the strong signal of this dense Alaskan smoke (denoted by the red arrows) as it moved from east to west over the far southern Arctic Ocean and along the far northern coast of Russia from 06-10 July. The Aerosol Index signal seemed to stall north of Scandinavia on 12-13 July, but then a small portion began to move toward Iceland and Greenland on 13-15 July around the periphery of a large upper-level low (500 hPa analyses). Finally, some of this smoke was then transported eastward across the Atlantic Ocean around the southern periphery of this upper-level low on 17 July, as was seen on the Meteosat-10 visible images at the beginning of this blog post.

Suomi NPP OMPS Aerosol Index images, covering the period 04-17 July [click to enlarge]

Suomi NPP OMPS Aerosol Index images, covering the period 04-17 July [click to enlarge]

CALIOP lidar data from the CALIPSO satellite (below) showed the vertical distribution of the Alaskan smoke over and off the coast of northern Norway on 11 July. The signal of the smoke was located in the center portion of the images; while there appeared to be some smoke at various altitudes within the middle to upper troposphere, a significant amount of smoke was seen in the lower stratosphere in the 10-12 km altitude range.

CALIPSO CALIOP lidar data showing the smoke over northern Norway on 11 July [click to enlarge]

CALIPSO CALIOP lidar data showing the smoke over northern Norway on 11 July [click to enlarge]

Unusual Double Eyewall structure in Himawari-8 Infrared Imagery of Typhoon Nangka

July 13th, 2015
Himawari-8 10.35 µm infrared imagery, 0540-1540 UTC on 13 July 2015 (Click to animate)

Himawari-8 10.35 µm infrared imagery, 0540-1540 UTC on 13 July 2015 (click to animate)

Himawari-8 10.35 µm infrared imagery showed an unusual (for infrared imagery) double-eyewall structure in Typhoon Nangka over the western Pacific Ocean on 13 July 2015. For such a feature to appear in infrared imagery, the secondary circulations of both the inner and outer eyewall need to be intense enough to support the downdraft/cloud-clearing necessary to create the “moats” between them. Microwave imagery of the storm, below, viewed via MIMIC (from this site), also showed the double eyewall structure quite well. This double-eyewall signature typically indicates that a tropical cyclone is experiencing an eyewall replacement cycle (ERC), which signals that a (temporary) decrease in intensity is soon to follow.

MIMIC imagery of Typhoon Nangka, 0000 - 1200 UTC on 13 July 2015 (Click to enlarge)

MIMIC imagery of Typhoon Nangka, 0000 – 1200 UTC on 13 July 2015 (click to enlarge)

Several hours later, a DMSP SSMIS 85 GHz microwave image at 1756 UTC, below, indicated that the ERC was essentially complete. Subsequently, the Joint Typhoon Warning Center slightly downgraded the intensity of Typhoon Nangka for their 21 UTC advisory. While not as well-defined as in the Himawari-8 imagery, the double-eyewall signature was still evident in the lower-resolution (4-km, vs  2-km) MTSAT-2 IR imagery (animation).

DMSP SSMIS 85 GHz microwave image and MTSAT-2 10.8 µm Infrared image (click to enlarge)

DMSP SSMIS 85 GHz microwave image and MTSAT-2 10.8 µm Infrared image (click to enlarge)

The Himawari-8 Target Sector was centered over Typhoon Nangka during this time; an IR image animation with a 2.5-minute timestep, below (courtesy of William Straka, SSEC), showed the evolution of the double eyewall signature, along with 2 pulses of storm-top gravity waves which propagated radially outward away from the center in the northern semicircle of the typhoon.

Himawari-8 10.4 µm IR channel images (click to animate large 115-Megabyte file)

Himawari-8 10.4 µm IR channel images (click to animate large 115-Megabyte file)

Hurricane Blanca in the eastern Pacific Ocean

June 4th, 2015
Suomi NPP VIIRS Day Night Band 0.70 µm Visible and 11.35 µm infrared imagery over Blanca, 0829 UTC 4 June 2015 (Click to enlarge)

Suomi NPP VIIRS Day Night Band 0.70 µm Visible and 11.35 µm infrared imagery over Blanca, 0829 UTC 4 June 2015 (Click to enlarge)

Suomi NPP overflew Hurricane Blanca early in the morning on 4 June, during a near-full Moon, and the Day Night Band imagery, above, toggled with the 11.35 µm imagery, show the hurricane. (Day/night band imagery of the eye is here, the entire storm is here, and zoomed out is here; click for 11.35 µm imagery of the eye, the entire storm, and zoomed out). Deep convection overnight did not wrap all the way around the storm. Evidence of dry air entrained into the circulation is apparent.

GOES-15 Imager 10.7 µm infrared channel images (click to play animation)

GOES-15 Imager 10.7 µm infrared channel images (click to play animation)

The 3-hourly animation of 10.7 micron imagery, above, from 3-4 June 2015 shows Hurricane Blanca southwest of the Mexican coast, drifting southwestward. Cold cloud tops that were apparent at the start of the loop warm by the end, perhaps because convection is being suppressed by the presence of dry air. MIMIC Total Precipitable Water (below) suggests that dry air is being entrained into Blanca’s circulation from the north. (Update on Andres, also apparent in the MIMIC Total Precipitable Water animation: This overlay of Metop ASCAT winds on top of GOES 10.7 imagery from ~0530 UTC on June 4 shows a swirl that is offset from the convection. Andres is forecast to become post-tropical later on June 4.)

MIMIC Total Precipitable Water animation for the 72 hours ending 1300 UTC on 4 June 2015 (click to enlarge)

MIMIC Total Precipitable Water animation for the 72 hours ending 1300 UTC on 4 June 2015 (click to enlarge)

Visible imagery from GOES-13 from June 3 and June 4, below, show a less distinct/cloudier eye on 4 June compared to 3 June. Multiple overshooting tops persist in the circulation of the system, but the coarse 30-minute temporal resolution of the imagery cannot capture the lifecycle of these quickly evolving events.

GOES-13 Imager 0.63 µm visible channel images (click to play animation)

GOES-13 Imager 0.63 µm visible channel images (click to play animation)

Water vapor imagery from GOES-13 from June and June 4, below, also confirm a consistently less organized storm. The dry air penetrating from the north is apparent in the imagery, but it appears not to have entered into the circulation of the storm, at least not at levels detected by the water vapor channel.

GOES-13 Imager 6.5 µm infrared water vapor channel images (click to play animation)

GOES-13 Imager 6.5 µm infrared water vapor channel images (click to play animation)

Morphed Microwave Imagery (MIMIC) from this website shows the evolution of the central eye structure, below. The eyewall that was much closer to the storm center at the start of the animation has been replaced by a weaker, larger eyewall.

Morphed Microwave Imagery, 48 hours ending 1500 UTC 4 June 2015 (click to enlarge)

Morphed Microwave Imagery, 48 hours ending 1500 UTC 4 June 2015 (click to enlarge)

For more information on this storm, please visit the National Hurricane Center website or the SSEC/CIMSS Tropical Weather website.

Andres and Blanca in the eastern Pacific

June 2nd, 2015
GOES-15 Imager 0.64 µm visible channel images (click to play animation)

GOES-15 Imager 0.64 µm visible channel images (click to play animation)

Hurricane Andres (above) in the eastern tropical Pacific was on 2 June 2015 joined by Tropical Storm Blanca (below). Blanca was forecast to become a Hurricane later on 2 June as Andres weakens. The circulation of Andres, above, is well-established, with good anti-cyclonic outflow and curved inflow bands. Shear values are low. (Graphics come from this site). However, Andres has moved over relatively cool Sea Surface Temperatures that spell weakening.

GOES-15 Imager 0.64 µm visible channel images (click to play animation)

GOES-15 Imager 0.64 µm visible channel images (click to play animation)

Blanca, in contrast, has a circulation that is not so well-defined. However, the storm is over very warm water, and also in a region of relatively low shear. Strengthening is forecast.

The animation of Andres at top shows a ragged appearance as dry air intrudes upon the circulation from the south and west. This dry air is apparent in the MIMIC Total Precipitable Water animation below. The circulation of Blanca appears at the end of the animation, embedded within a rich source of tropical moisture.

3-day animation of MIMIC Total Precipitable Water over the eastern Pacific (click to enlarge)

3-day animation of MIMIC Total Precipitable Water over the eastern Pacific (click to enlarge)

Sea-surface temperatures off the Pacific Coast of Mexico have been warmer than normal for much of this year (Map, data from here). Warmer-than-normal sea-surface temperatures argue for stronger hurricanes, and Andres was a Category 4 storm on 1 June with a well-developed eye. Andres is one of only 5 May storms in the eastern Pacific since 1970 to achieve Major Hurricane status (Link).

Aqua overflew Andres shortly before 1800 UTC on 1 June, and the water vapor imagery of the storm at that time is here. The True-Color imagery is shown below.

Aqua True-Color Imagery, 1748 UTC on 1 June 2015 (click to enlarge)

Aqua True-Color Imagery, 1748 UTC on 1 June 2015 (click to enlarge)

A storm-centered animation over Andres’ lifecycle is shown below. The storm starts in the moisture-rich ITCZ and ends as an isolated region of moisture surrounded by dryness.

GOES-15 Water Vapor Infrared Imagery (6.5µm) centered on Andres' center (click to animate)

GOES-15 Water Vapor Infrared Imagery (6.5µm) centered on Andres’ center (click to enlarge)

For further information on these storms, consult the National Hurricane Center website.