GCOM-W1 AMSR2 microwave products

November 30th, 2018 |

GCOM-W! AMSR2 Total Precipitable Water and Wind Speed products, from 2256 UTC on 28 November to 1692 UTC on 30 November [click to play animation]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products, from 2256 UTC on 28 November to 1692 UTC on 30 November [click to play animation]

A series of GCOM-W1 AMSR2 swaths during the period from 2256 UTC on 28 November to 1692 UTC on 30 November 2018 (above) showed the global coverage of Total Precipitable Water and Wind Speed products from that polar-orbiting satellite.

GCOM-W1 AMSR2 Total Precipitable Water, Wind Speed, Surface Rain Rate and Cloud Liquid Water products [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water, Wind Speed, Surface Rain Rate and Cloud Liquid Water products [click to enlarge]

A closer look just south of the Atlantic provinces of Canada (above) showed a comparison of Total Precipitable Water, Wind Speed, Surface Rain Rate and Cloud Liquid Water products over a strong mid-latitude cyclone at 0545 UTC on 29 November (the 0532 UTC time stamp on the images denotes the beginning time of that particular satellite swath).

Surface analyses from the OPC (below) classified this low pressure system as Hurricane Force at 00 UTC and Storm Force at 06 UTC — however, AMSR2 ocean surface wind speeds were as high as 71 knots west of the surface low, 84.8 knots north of the low and 95.6 knots in the vicinity of the occluded front.

Surface analyses at 00 UTC and 06 UTC [click to enlarge]

Surface analyses at 00 UTC and 06 UTC [click to enlarge]

Shortly after the overpass of GCOM-W1, additional views of the western portion of this storm were provided by Aqua MODIS and NOAA-20 VIIRS (below). (note: the NOAA-20 VIIRS images are incorrectly labeled as Suomi NPP)

Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images at 0543 UTC [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images at 0543 UTC [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0557 UTC [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0557 UTC [click to enlarge]

Another overpass of GCOM-W1 about 10 hours later continued to show a broad region of strong post-frontal westerly winds to the south of the storm center (below). During that period, the occluded low continued to deepen from 957 to 952 hPa (surface analyses).

GCOM-W1 AMSR2 Total Precipitable Water, Wind Speed at 0532 and 1529 UTC [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products at 0532 and 1529 UTC [click to enlarge]

Additional features seen in the AMSR2 Total Precipitable Water and Wind Speed products in other parts of the world included the following:

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products at 0353 UTC on 29 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products south of Iceland at 0353 UTC on 29 November [click to enlarge]

Low pressure south of Iceland (surface analyses), with an ocean surface wind speed of 76 knots (above).

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products off the US West Coast at 1026 UTC on 29 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products off the US West Coast at 1026 UTC on 29 November [click to enlarge]

Low pressure off the US West Coast (surface analyses), with an ocean surface wind speed of  70 knots (above).

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products north of Hawai'i at 1202 UTC on 29 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products north of Hawai’i at 1202 UTC on 29 November [click to enlarge]

Low pressure and a cold front northwest of Hawai’i (surface analysis), with a long fetch of tropical moisture and widespread ocean surface wind speeds of 60-70 knots (above).

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products southwest of Australia at 1659 UTC on 29 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products southwest of Australia at 1659 UTC on 29 November [click to enlarge]

Low pressure southwest of Australia, with an ocean surface wind speed of 47 knots (above).

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products southeast of Argentina at 1659 UTC on 29 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products southeast of Argentina at 1659 UTC on 29 November [click to enlarge]

Low preesure and a cold front southeast of Argentina, with TPW as high as 2.2 inches and an ocean surface wind speed of 58.6 knots (above).

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products over the North Sea at 0259 UTC on 30 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products over the Norwegian Sea at 0259 UTC on 30 November [click to enlarge]

Low pressure over the Norwegian Sea (surface analysis), with an ocean surface wind speed of 75 knots (above).

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products over the Aleutian Islands at 1247 UTC on 30 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products over the Aleutian Islands at 1247 UTC on 30 November [click to enlarge]

A plume of moisture and strong winds ahead of a low pressure and cold front (surface analysis) moving across the Aleutian Islands (above).

Due to the frequent overlap of polar-orbiting satellite swaths at high latitudes, some locations can have data coverage from numerous consecutive overpasses. The example below shows the Barents Sea — between 70-80º N latitude — during 7 consecutive swaths from 2256 UTC on 28 November to 0847 UTC on 29 November.

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products over the Barents Sea from 2256 UTC on 28 November to 0847 UTC on 29 November [click to enlarge]

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products over the Barents Sea from 2256 UTC on 28 November to 0847 UTC on 29 November [click to enlarge]

Train of standing waves south of Hawai’i

November 25th, 2018 |
GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed an interesting train of standing waves about 100-150 miles south of the Big Island of Hawai’i on 25 November 2018. With the presence of moisture aloft, the 3 water vapor weighting functions — calculated using the 00 UTC Hilo sounding — were shifted to high enough altitudes to eliminate the sensing of radiation from features in the lower troposphere. There were no pilot reports of turbulence in the vicinity of these standing waves — but they were located outside of the primary commercial air traffic corridors to/from the islands.

GOES-17 “Clean” Infrared Window (10.3 µm) and Near-Infrared “Cirrus” (1.37 µm) images (below) showed that these wave clouds were radiometrically transparent to longwave thermal energy being emitted from/near the surface — note that marine boundary layer stratocumulus clouds could be seen drifting westward within the easterly trade wind flow. As a result, the satellite-sensed 10.3 µm infrared brightness temperatures of the standing wave clouds were significantly warmer than that of the air at higher altitudes where they existed. These standing wave cloud features were, however, very apparent in 1.37 µm Cirrus imagery, along with what appeared to be other thin filaments of cirrus cascading southward overhead. The southward motion of the features seen on Cirrus imagery suggests that they existed at pressure levels of 370 hPa (26,900 feet / 8.2 km) or higher — altitudes where northerly winds were found on the Hilo sounding.

GOES-17 "Clean" Infrared Window (10.3 µm) and Near-Infrared "Cirrus" (1.37 µm) images [click to play animation | MP4]

GOES-17 “Clean” Infrared Window (10.3 µm) and Near-Infrared “Cirrus” (1.37 µm) images [click to play animation | MP4]

A comparison of all 16 ABI spectral bands is shown below. Note that in the longwave infrared bands along the bottom 4 panels, the brightness temperatures are progressively colder (darker shades of green) on the 11.2 µm, 12.3 µm and 13.3 µm images — each of these bands are increasingly affected by water vapor absorption aloft, therefore more effectively sensing the thin layer of higher-altitude standing wave clouds. AWIPS cursor sampling showed the differences in detected brightness temperature at 3 different points along the feature: here, here and here. The increasing sensitivity to radiation emitted from higher altitudes can also be seen in a comparison of weighting functions for ABI bands 13, 14, 15 and 16.

GOES-17 images of all 16 ABI bands [click to play animation | MP4]

GOES-17 images of all 16 ABI spectral bands [click to play animation | MP4]

GOES-15 (GOES-West) Water Vapor (6.5 µm), Infrared Window (10.7 µm) and Infrared CO2 (13.3 µm) images (below) showed that the lower spatial resolution of the legacy GOES Imager infrared bands (4 km at satellite sub-point) was not able to resolve the individual waves as well as the 2-km GOES-17 ABI images . Also, as was seen with the GOES-17 imagery, the 13.3 µm CO2 brightness temperatures of the standing wave clouds were significantly colder (shades of blue) compared to those of the conventional 10.7 µm Infrared Window. The corresponding GOES-15 Visible imagery (0.63 µm) is also available: animated GIF | MP4.

GOES-15 Water Vapor (6.5 µm, keft), Infrared Window (10.7 µm, center) and Infraered CO2 (13.3 µm, right) images [click to play animation | MP4]

GOES-15 Water Vapor (6.5 µm, keft), Infrared Window (10.7 µm, center) and Infraered CO2 (13.3 µm, right) images [click to play animation | MP4]

In comparisons of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 visualized using RealEarth (below), note the highly-transparent nature of the standing wave clouds on the RGB images; only the earliest 2256 UTC VIIRS 11.45 µm image displayed brightness temperatures of -20ºC and colder (cyan to blue enhancement).

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2256 UTC [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2256 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2336 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2336 UTC [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0028 UTC [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0028 UTC [click to enlarge]

Terra (at 2043 UTC) and Aqua (at 2347 UTC) MODIS True Color RGB images along with retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure from the WorldView site (below) indicated that the standing wave feature was composed of ice crystal clouds exhibiting temperature values of -53ºC and colder (dark purple enhancement) located at heights of 12 km or higher (and at pressure levels at or above 250 hPa). These temperature/height/pressure values roughly corresponded to the upper portion of a layer of increasing relative humidity between 200-274 hPa on the Hilo sounding.

Terra MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2043 UTC [click to enlarge]

Terra MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2043 UTC [click to enlarge]

Aqua MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2347 UTC [click to enlarge]

Aqua MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2347 UTC [click to enlarge]

However, an experimental CLAVR-x version of GOES-17 Cloud Type, Cloud Top Temperature and Cloud Top Height products (below; courtesy of Steve Wanzong, CIMSS) indicated Cirrus clouds having temperature values in the 210-200 K (-63 to -73ºC) range at heights within the 13-16 km range. These colder/higher values raise the question of whether the wave clouds might have formed and been ducted within the shallow temperature inversion near 15 km on the Hilo sounding.

GOES-17 Cloud Type product [click to play animation | MP4]

GOES-17 Cloud Type product [click to play animation | MP4]

GOES-17 Cloud Top Temperature product [click to play animation | MP4]

GOES-17 Cloud Top Temperature product [click to play animation | MP4]

GOES-17 Cloud Top Height product [click to play animation | MP4]

GOES-17 Cloud Top Height product [click to play animation | MP4]

GOES-17 False Color RGB images (below) vividly portrayed the transparent nature of the high-altitude standing wave cloud feature, which allowed westward-moving stratocumulus clouds within the marine boundary layer to plainly be seen. The RGB components are 1.38 µm / 0.64 µm /  1.61 µm.

GOES-17 False Color RGB images [click to play animation | MP4]

GOES-17 False Color RGB images [click to play animation | MP4]

A coherent explanation of this feature and what caused it to form remains elusive, earning it a distinguished place in the what the heck is this? blog category. Perhaps one clue existed in the winds aloft, as depicted by the NAM at 200 hPa, 250 hPa and 300 hPa (below), which showed northerly/northeasterly flow that was decelerating as it entered a trough axis (the region within the red box). Could this flow deceleration have induced a “reverse flow” which then caused enough weak lift to form the thin standing wave clouds within the aforementioned semi-moist 200-274 hPa layer seen on the Hilo sounding? No other obvious forcing mechanisms were in the immediate area — a slowly-approaching surface cold front was too far north of Hawai’i to have played a role.

NAM Winds at 200 hPa, 250 hPa and 300 hPa [click to enlarge]

NAM Winds at 200 hPa, 250 hPa and 300 hPa [click to enlarge]

Eruption of Mount Veniaminof on the Alaska Peninsula

November 21st, 2018 |
GOES-17

GOES-17 “Red” Visible (0.64 µm) and Split Window Difference (10.3-12.3 µm) images [click to play MP4 animation]

* GOES-17 images posted here are preliminary and non-operational *

Following an eruption of Mount Veniaminof on 21 November 2018, 1-minute Mesoscale Domain Sector GOES-17 “Red” Visible (0.64 µm) and Split Window Difference (10.3-12.3 µm) images (above) showed the volcanic ash plume drifting southeastward over the Gulf of Alaska. During the period 1947-2323 UTC the plume was seen to grow to a length of 200 miles from the volcano summit. Note in the Visible imagery that the 2625 ft (800 m) volcano acted as a barrier to the northwesterly boundary layer winds to create a cloud-free “notch” immediately downwind of Veniaminof.

NOAA-20 VIIRS True Color RGB images viewed using RealEarth (below) highlighted the light brown color of the ash plume.

NOAA-20 VIIRS True Color RGB images [click to enlarge]

NOAA-20 VIIRS True Color RGB images [click to enlarge]

A sequence of retrieved Ash Probability, Ash Height and Ash Loading (source) derived from Terra/Aqua MODIS and Suomi NPP VIIRS data (below) indicated high probabilities of ash content, height values primarily in the 4-6 km range and ash loading exceeding 4 g/m3 at times.

Terra/Aqua MODIS and Suomi NPP VIIRS Ash Probability, Ash Height and Ash Loading images [click to play animation | MP4]

Terra/Aqua MODIS and Suomi NPP VIIRS Ash Probability, Ash Height and Ash Loading images [click to play animation | MP4]

 

Increasing ice concentration in Hudson Bay

November 21st, 2018 |

Sea ice concentration derived from AMSR2 data, 06-21 November [click to play animation | MP4]

Daily sea ice concentration derived from AMSR2 data, 06-21 November [click to play animation | MP4]

After increasingly colder air began moving from eastern Nunavut across Hudson Bay beginning on 06 November (surface analyses), the daily sea ice concentration as derived from GCOM-W1 AMSR2 data (source) began to increase in the northern half of Hudson Bay (above) — especially after 15 November once mid-day (18 UTC) temperatures colder than -20ºF were seen at reporting stations along the northwest coast.

A sequence of daily Terra/Aqua MODIS True Color Red-Green-Blue (RGB) images (source) showed signatures of the increasing of ice coverage.

Terra/Aqua MODIS True Color RGB images, 06-21 November [click to play animation | MP4]

Daily Terra/Aqua MODIS True Color RGB images, 06-21 November [click to play animation | MP4]

A toggle between Terra MODIS True Color and False Color RGB images on 21 November (below) confirmed that much of the northern half of Hudson Bay contained ice — snow/ice (as well as ice crystal clouds) appear as darker shades of red in the False Color image (in contrast to the cyan shades of supercooled water droplet clouds).

Terra MODIS True Color and False Color RGB images on 21 November [click to enlarge]

Terra MODIS True Color and False Color RGB images on 21 November [click to enlarge]

19 November maps of Ice Concentration, Ice Stage and Departure from Normal via the Canadian Ice Service (below) further characterized this ice formation, which was ahead of normal for the central portion of Hudson Bay.

Ice Concentration [click to enlarge]

Ice Concentration [click to enlarge]

Ice Stage [click to enlarge]

Ice Stage [click to enlarge]

Ice Concentration Departure [click to enlarge]

Ice Concentration Departure [click to enlarge]