Asian dust entrained into a midlatitude cyclone

May 12th, 2019 |

True Color RGB images from MODIS (Terra) and VIIRS (NOAA-20 and Suomi NPP) [click to enlarge]

True Color RGB images from MODIS (Terra) and VIIRS (NOAA-20 and Suomi NPP) [click to enlarge]

True Color Red-Green-Blue (RGB) images from the MODIS instrument (on the Terra satellite) and the VIIRS instrument (on the NOAA-20 and Suomii NPP satellites) as viewed using RealEarth (above) revealed a tan-colored swirl of dust that had been lofted from the surface and entrained into the circulation of a midlatitude cyclone along the Mongolia/China border on 12 May 2019.

A sequence of MODIS/VIIRS True Color RGB images from Terra and Suomi NPP on 10, 11 and 12 May (below) showed the initial signature of surface-based blowing dust appearing in the Kumul and Jiuquan areas of northwestern China on 11 May, before it became wrapped into the circulation of the aforementioned midlatitude cyclone on 12 May.

True Color RGB images from MODIS (Terra) and VIIRS (Suomi NPP) [click to enlarge]

True Color RGB images from MODIS (Terra) and VIIRS (Suomi NPP) [click to enlarge]

Surface analyses at 3-hour intervals (source), from 12 UTC on 11 May to 00 UTC on 13 May (below) illustrated the strong pressure gradient between a large dome of high pressure over Mongolia and a developing midlatitude cyclone along the Mongolia/China border on 11 May — strong surface winds generated by this pressure gradient initially caused the blowing dust to begin in northwestern China.

Surface analyses at 3-hour intervals from 12 UTC on 11 May to 00 UTC on 13 May [click to enlarge]

Surface analyses at 3-hour intervals from 12 UTC on 11 May to 00 UTC on 13 May [click to enlarge]

JMA Himawari-8 Split Window Difference (10.4-12.3 µm) images (below) showed the signature of dust (yellow to cyan enhancement) moving eastward from the desert source region in northwestern China and becoming wrapped into the circulation of the midlatitude cyclone along the Mongolia/China border.

Himawari-8 Split Window Difference (10.4-12.3 µm) iimages [click to play animation |MP4]

Himawari-8 Split Window Difference (10.4-12.3 µm) images [click to play animation | MP4]

Ash fall streak from the Sheveluch volcano in Kamchatka

May 12th, 2019 |

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images, with topography [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images, with topography [click to enlarge]

In a comparison of Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images on 12 May 2019 (above), a dark volcanic ash fall streak was evident in the Visible image, which extended over 100 miles southward from the Sheveluch volcano on the Kamchatka Peninsula of Russia. This feature was a layer of volcanic ash that had been deposited on top of existing snow cover — note that most of the dark ash fall streak exhibited much cooler infrared brightness temperatures compared to the bare ground of the interior valley to the west (since the ash streak existed on top of a higher-altitude area of snow cover).

This ash fall streak was a result of an explosive eruption of the volcano over a month earlier, on 10 April — the volcanic ash plume could be seen moving southward in Himawari-8 Visible (0.64 µm) images (below).

Himawari-8

Himawari-8 “Red” Visible (0.64 µm) images [click to play animation | MP4]

An interesting aspect of this long-lived ash fall streak was that a portion of it was apparently covered by a layer of fresh snowfall at some point after the eruption — and a 7-day sequence of Suomi NPP VIIRS True Color Red-Green-Blue (RGB) images viewed using RealEarth (below) suggested that this layer of new snow was melting with the aid of the high May sun angle, gradually revealing more of the original length of the ash fall streak.

Suomi NPP VIIRS True Color RGB images, 06-12 May 2019 [click to play animation | MP4]

Suomi NPP VIIRS True Color RGB images, 06-12 May 2019 [click to play animation | MP4]

Note that there was another small volcanic plume moving south-southwestward from Sheveluch in the 09 May VIIRS True Color image — retrieved quantities of ash probability, height, loading and effective radius for this volcanic plume (source) are shown below.

Suomi NPP False Color, Ash Probability, Height, Loading and Effective Radius [click to enlarge]

Suomi NPP False Color, Ash Probability, Height, Loading and Effective Radius [click to enlarge]

This type of volcanic ash fall streak frequently occurs on the snow-covered Kamchatka Peninsula — here is an example from March 2013.

Thanks go out to Santiago Gassó for bringing this interesting feature to our attention.

Pyrocumulonimbus cloud in eastern Russia

April 30th, 2019 |

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.4 µm, bottom) [click to play animation | MP4]

On 30 April, JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed the formation of the first known pyrocumulonimbus (pyroCb) cloud of the 2019 Northern Hemisphere wildfire season. The pyroCb developed within the warm sector of an approaching midlatitude cyclone (surface analyses) in the Russian Far East, between still-ice-covered Lake Bolon and the Amur River. The cloud-top infrared brightness temperature first reached the -40ºC “pyroCb threshold” at 0310 UTC; note that the pyroCb cloud top appears warmer (darker shades of gray) than those of surrounding thunderstorms in the Shortwave Infrared images — a characteristic of enhanced solar reflection off the smaller ice crystals that are found in pyroCb cirrus anvils.

A faster animation revealed the rapid northeastward run of the large pyroCb-producing fire on Shortwave Infrared imagery.

VIIRS True Color RGB and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

In a sequence of three VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP as viewed using RealEarth (above), the coldest cloud-top infrared brightness temperature of the pyroCb was -59ºC — which closely corresponded to the tropopause temperature on 00 UTC rawinsonde data from Habarovsk (below), located just southwest of the fire region.

Plot of 00 UTC rawinsonde data from Habarovsk [click to enlarge]

Plot of 00 UTC rawinsonde data from Habarovsk [click to enlarge]

Ice in the Sea of Okhotsk

April 18th, 2019 |

Himawari-8

Himawari-8 “Red” Visible (0.64 µm) images [click to play animation | MP4]

JMA Himawari-8 “Red” Visible (0.64 µm) images (above) revealed circulations of ice within the Sea of Okhotsk (east of Sakhalin Island — station identifier UHSS is Yuzhno-Sakhalinsk, Russia) on 17-18 April 2019. Wind stress from an occluded Gale Force Low moving through that region on the previous day (surface analyses) likely helped to enhance some of the ice circulations.

In a comparison of Himawari-8 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below), note that the ice appears much darker than cloud features (since ice is a strong absorber of radiation at the 1.61 µm wavelength).

Himawari-8 "Red" Visible (0.64 µm, left) and Near-Infrared "Snow/Ice" (1.61 µm, right) images [click to play animation | MP4]

Himawari-8 “Red” Visible (0.64 µm, left) and Near-Infrared “Snow/Ice” (1.61 µm, right) images [click to play animation | MP4]

Thanks to Thomas Birchard (NWS Honolulu) for bringing this interesting feature to our attention!