High-altitude waves over the Arctic

March 27th, 2020 |

GOES-17

GOES-17 “Ozone” (9.61 µm) images, with rawinsonde sites plotted in yellow [click to play animation | MP4]

GOES-17 (GOES-West) “Ozone” (9.61 µm) images (above) revealed waves propagating northwestward over northern Alaska, northern Yukon and the adjacent Beaufort Sea during the pre-dawn hours on 27 March 2020. That area was too illuminated by either aurora borealis or the rising sun — so Suomi NPP VIIRS Day/Night Band (0.7 µm) imagery could not confirm the presence of mesospheric airglow waves (see this blog post for some examples).

A plot of the GOES-17 “Ozone” spectral band weighting function — calculated using 12 UTC rawinsonde data from Fairbanks, Alaska — showed a peak contribution from within the stratosphere at the 39 hPa pressure level, corresponding to an altitude around 21 km (below).

Plot of GOES-17

Plot of GOES-17 “Ozone” (9.61 um) weighting function, calculated using 12 UTC rawinsonde data from Fairbanks, Alaska [click to enlarge]

The curious aspect of these waves was their northwestward propagation — rawinsonde data from 3 sites across the region (below) indicated that the winds aloft within the upper troposphere and throughout the stratosphere were strong northwesterly, which meant the waves were moving against the ambient flow. Lacking a coherent, science-based explanation for these wave features, this blog post earns its place in the “What the heck is this?” category.

Plots of rawinsonde data from Fairbanks, Alaska [click to enlarge]

Plots of rawinsonde data from Fairbanks, Alaska [click to enlarge]

Plots of rawinsonde data from Utqiagvik (formerly Barrow), Alaska [click to enlarge]

Plots of rawinsonde data from Utqiagvik (formerly Barrow), Alaska [click to enlarge]

Plots of rawinsonde data from Inuvik, Northwest Territories [click to enlarge]

Plots of rawinsonde data from Inuvik, Northwest Territories [click to enlarge]

Year-long Animations of Visible and Infrared Images

March 26th, 2020 |

True-color visible imagery global montage from 6 March 2019 – 5 March 2020 (Click to launch containerized YouTube Vide)

A previous blog post (here) has shown 1-month animations of true-color visible imagery from geostationary satellites (GOES-16, GOES-17, Himawari-8, Meteosat-11 and others) wherein local noon longitudinal strips are blended together to create a global view. (Imagery courtesy Rick Kohrs, SSEC) (See also this blog post for an explanation). The animation above (Click it to view a YouTube animation within a container) shows visible true-color imagery for each day from 6 March 2019 through 5 March 2020.

The infrared imagery below combines the ‘clean window’ Band 13 channel on GOES-16 and GOES-17 (10.3 µm on both) with Band 13 on Himawari-8 (10.4 µm) and shows 2019 data at 6-h intervals.

Color-enhanced Window Channel infrared (ABI: 10.3 µm; AHI: 10.4 µm) imagery from 2019 (Click to launch containerized YouTube Vide)

Rapidly intensifying storm in the North Pacific Ocean

March 4th, 2020 |

GOES-17 Mid-level (6.9 µm) and Air Mass RGB images [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm) and Air Mass RGB images [click to play animation | MP4]

GOES-17 (GOES-West) Mid-level Water Vapor (6.9 µm) and Air Mass RGB images (above) depicted a rapidly intensifying Storm Force low (surface analyses) moving from the North Pacific Ocean toward the Alaska Panhandle on 04 March 2020. A comparison of GOES-17 Mid-level Water Vapor and Air Mass RGB images with NAM40 PV1.5 pressure (below) showed that the Dynamic Tropopause — taken to be the pressure of the Potential Vorticity 1.5 surface — had descended to the 650 hPa pressure level in the vicinity of the low at 1200 UTC. The deeper red hues on Air Mass RGB imagery also indicated the presence of ozone-rich stratospheric air within the atmospheric column as the tropopause lowered in the vicinity of the rapidly-deepening low pressure.

GOES-17 Mid-level (6.9 µm) and Air Mass RGB images, with NAM40 PV1.5 pressure [click to enlarge]

GOES-17 Mid-level Water Vapor (6.9 µm) and Air Mass RGB images, with NAM40 PV1.5 pressure [click to enlarge]

1-minute Mesoscale Domain Sector GOES-17 “Red” Visible (0.64 µm) images (below) revealed mesovortices within the core of the large low pressure system.

GOES-17 "Red" Visible (0.64 µm) images [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

===== 05 March Update =====

GOES-17

GOES-17 “Clean” Infrared Window (10.35 µm) mages [click to play animation | MP4]

On the following day, GOES-17 “Clean” Infrared Window (10.35 µm) mages (above) showed clouds associated with the Storm Force low as it moved slowly northward near the coast of the Alaska Panhandle (surface analyses). The storm prompted a wide variety of advisories, including a High Wind Warning for the Juneau area and a Blizzard Warning for the Skagway area.


GOES-17 True Color Red-Green-Blue (RGB) images created using Geo2Grid (below) revealed several plumes of airborne glacial silt drifting over the Gulf of Alaska, lofted by a strong offshore gap winds. A ship near Prince William Sound reported blowing dust at 18 UTC. Also seen in the images was the northwestward drift of ice into Cook Inlet and Turnagain Arm as high tide approached.

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

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

GOES-17 IFR Probability Fields are now available via LDM Feed

March 3rd, 2020 |

GOES-17 IFR Probability Fields and Night Fog Brightness Temperature Difference (10.3 µm – 3.9 µm) fields, 1311 UTC on 3 March 2020 (Click to enlarge)

When GOES-15 stopped sending data, IFR Probability fields based on GOES-15 ceased being sent over LDM to users. CIMSS is now sending GOES-17 IFR Probability fields (shown in a toggle above with the Night Fog Brightness Temperature Difference field) via the EXP LDM feed from CIMSS.  Particular strengths of IFR Probability fields include giving a useful low cloud signal below high clouds (as over the western Olympic Peninsula in Washington) and differentiating between elevated stratus and fog, as in the northern Willamette Valley in Oregon.

Note that the Brightness Temperature Difference field shows artifacts related to GOES-17’s poorly-functioning Loop Heat Pipe.  Those artifacts are rapidly diminish day-to-day in early March as GOES-17 enters eclipse season.  Blog posts that discuss GOES-17 IFR Probability are available <a href=”https://fusedfog.ssec.wisc.edu/?cat=36″>here</a>.