10-minute interval GOES-16 (GOES-East) True Color RGB images (source) from 0930-1900 UTC on 13-26 November 2023 (above) showed Iceberg A23a just east-northeast of Joinville Island (at the tip of the Antarctic Peninsula). Although cloud-free periods were scarce during those 14 days, even on most of the cloudy days the silhouette of A23a was evident. During that time, A23a was the largest iceberg in the world (although it was smaller in area than recent icebergs such as A68).

On 2 days in mid-November when cloud cover was at a minimum, a toggle between “Natural Color” RGB images from Landsat-9 (at 1239 UTC on 14 November) and Landsat-8 (at 1233 UTC on 15 November) is shown below (source) — which revealed a small amount of westward drift during that 24-hour period.

While the NOAA-20 VIIRS Sea Ice Temperature derived product at 0000 UTC on 13 November (below) generally displayed values near or just below freezing (medium shades of orange) across much of the surface of A23a, there were some areas across the northern portion of the iceberg that exhibited above-freezing values (darker shades of orange) as warm as 274.4 K or +1.25C (suggesting that some surface melting was occurring).

However, on 27 November GOES-16 True Color RGB images (below) showed that fractures — likely induced by wind stress as an occluded cyclone moved across the area (surface analyses) — began developing within the southern and eastern portions of A23a.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Day Cloud Phase Distinction RGB images with an overlay of GLM Flash Extent Density (above) showed a glaciating (brighter shades of green) to glaciated (pale shades of yellow) lake effect snow (LES) band streaming inland off Lake Erie on 17 November 2023. There were 4 brief periods of lightning activity seen just south of the Buffalo, New York metro area. Note: since Flash Extent Density (FED) values were relatively low, the maximum value of the default FED colormap range was adjusted to 2.5 (to emphasize peaks within the low-FED areas).

A closer view (below) showed that the FED-indicated lightning activity was centered over the Southtowns (southern suburbs) of Boston — which had received up to 8.5 inches of snow by about 2300 UTC on 27 Novembver.

THUNDERSNOW Lake Erie at Hamburg Beach #NYwx pic.twitter.com/KpRqAXg5Qf

— BuffaloSnowKing (@BuffaloSnowKing) November 27, 2023

Cursor sampling of 2-km resolution GOES-16 CLAVR-x Cloud Top Temperature and Cloud Top Height derived products (below) indicated that the coldest cloud top temperatures within the lightning-producing LES band were in the -18 to -19°C range, with maximum cloud top heights in the 12000-13000 ft range.

During the next several hours, the LES cloud band slowly migrated southward — GOES-16 Nighttime Microphysics RGB images with an overlay of GLM Flash Extent Density (below) suggested that the cloud tops were mixed phase (ice crystals and supercooled water droplets — shades of tan to light brown), which is a necessary condition for charge separation processes within the cloud that lead to lightning production. Another favorable thundersnow factor was a sufficiently high -10°C air temperature level of 1.1 km (reference), as seen in 0000 UTC Buffalo rawinsonde data.

Beginning at 0253 UTC on 28 November, notable bursts of FED lightning activity were seen in the vicinity of Chautauqua County/Dunkirk Airport (KDKK) — which reported a thunderstorm (TS) that lasted from from 0257 UTC to 0312 UTC, and thundersnow (TSSN) at 0306 UTC (below). The surface visibility at that site dropped from 6 miles at 0310 UTC to 1-1/4 mile at 0320 UTC. Thanks to Rick DiMaio (Loyola University) for bringing these KDKK observations to our attention.

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GOES-East fire detection products in RealEarth allow users to assess burning areas across the Continental United States. In the example below, burning appears to be occurring in Lafayette Parish, Louisiana. These fire detections in southern Louisiana are picked up by the GOES scene fire detection and by the GOES fire temperature RGB (purple reddish area). This scene is associated with a fire radiative power (FRP) of 49.6. When adding HRRR smoke model output to the display, users can see that some near-surface smoke may be occurring nearby. However, the HRRR smoke is likely coming from a different location. The GOES scene fire detection is picking up many fires throughout the surrounding area.

Farther north in the state, in Caldwell Parish, the GOES algorithm picks up a fire scene with an even higher fire radiative powers (FRP up to 405.11). When observing with the GOES fire temperature RGB, this scene is even more apparent than the example in Lafayette Parish. However, the HRRR model output does not place any near-surface smoke there. This may be due to the model not receiving the latest satellite data input. (Note that the latest HRRR timestamp is at 1700Z while the GOES products are from 1731Z).

Users can recreate these scenes in RealEarth.

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The Community Satellite Processing Package (CSPP) allows a user to manipulate VIIRS data to create high-quality, full-resolution imagery (see, for example, this I05 example, and this Day Night Band example, and this I01 example). In addition to single-band images, imagery for products such as Advanced Clear Sky Processor for Ocean (ACSPO) sea-surface temperatures (SSTs) can also be created, as shown above. Polar2grid software is being used for all examples in this blogpost. It is a Linux-based software package that is available for free download here.

ACSPO SST data derived from VIIRS data are available online here (for Suomi-NPP) and here (for NOAA-20). Data files appear about 1-3 days after observation (a user with a Direct Broadcast antenna, of course, can process data for the needed SST files in near-real time); the two files I downloaded (from this source directly; it is also accessible via NOAA CLASS — see the note at the NOAA CLASS website and click through to the NOAA-20 site) include 10 minutes of VIIRS ACSPO observations from NOAA-20: from 09:00:00 to 09:09:59 and from 21:30:00 to 21:39:59) on 21 November 2023. This map (from this source) shows that the observations are over the Arabian Sea. The downloaded files have a file naming structure shown below

20231121090000-OSPO-L2P_GHRSST-SSTsubskin-VIIRS_N20-ACSPO_V2.80-v02.0-fv01.0.nc
20231121213000-OSPO-L2P_GHRSST-SSTsubskin-VIIRS_N20-ACSPO_V2.80-v02.0-fv01.0.nc

Several steps are needed before the imagery shown above is created. First, I defined a grid using Polar2Grid software (that is, p2g_grid_helper.sh) onto which the data are placed, because the orbit paths at 0900 and 2130 do not sample the same domain. That command is shown below.

$POLAR2GRID_HOME/bin/p2g_grid_helper.sh Arabian 63.5 14.6 2000 -2000 1440 1120 > $POLAR2GRID_HOME/Arabian.yaml

Because I know beforehand the range of sea-surface temperatures that are likely in November in the Arabian Sea, I can instruct (via a yaml file that I named “my_sst_rescale.yaml“) Polar2Grid to scale the computed SSTs appropriately. The contents of the file, that I placed in $POLAR2GRID_HOME/bin, are shown below. I’m constraining the temperatures to be between 15^oC and 35^oC.

enhancements:
  oman_sst:
    standard_name: sea_surface_subskin_temperature
    operations:
      - name: linear_stretch
        method: !!python/name:satpy.enhancements.stretch
        kwargs: {stretch: 'crude', min_stretch: 288.16, max_stretch: 308.16}

The polar2grid commands to (1) create the .tif file (run from the $POLAR2GRID_HOME/bin directory) is below, and (2) to apply a colormap to the two tif files (one at 0900, one at 2130) are shown below; the wildcard ‘20231121???0’ in the file name resolves the files containing both 0900 and 2130 UTC data. The two filenames created are shown beneath the polar2grid command. The add_colormap.sh command overwrites the .tif file, adding colormap information from the file p2g_sst_palette.txt, a colormap that is supplied with the polar2grid installation; a user could, of course, alter the colormap to something of their own choosing.

$POLAR2GRID_HOME/bin/polar2grid.sh -r acspo -w geotiff -p sst -g Arabian --grid-configs $POLAR2GRID_HOME/Arabian.yaml --fill-value 0 --extra-config-path my_sst_rescale.yaml -f /path/to/J01Data/20231121???0*SST*N20*

noaa20_viirs_sst_20231121_090000_Arabian.tif
noaa20_viirs_sst_20231121_213000_Arabian.tif

$POLAR2GRID_HOME/bin/add_colormap.sh $POLAR2GRID_HOME/colormaps/p2g_sst_palette.txt noaa20_viirs_sst_20231121_???000_Arabian.tif

The imagery above includes coastlines, borders, and a labeled colorbar. Those are all added with the following commands, one for each time.

$POLAR2GRID_HOME/bin/add_coastlines.sh --add-coastlines --add-borders --add-grid --grid-D 10 10 --grid-d 10 10 --grid-text-size 16 --add-colorbar --colorbar-text-color "white" --colorbar-text-size 20 --colorbar-title "N20 VIIRS ACSPO SST 21 November 2023 0900 UTC" --colorbar-height 32 --colorbar-tick-marks 4 --colorbar-min 15.0 --colorbar-max 35.0 --colorbar-units "°C" noaa20_viirs_sst_20231121_090000_Arabian.tif

$POLAR2GRID_HOME/bin/add_coastlines.sh --add-coastlines --add-borders --add-grid --grid-D 10 10 --grid-d 10 10 --grid-text-size 16 --add-colorbar --colorbar-text-color "white" --colorbar-text-size 20 --colorbar-title "N20 VIIRS ACSPO SST 21 November 2023 2130 UTC" --colorbar-height 32 --colorbar-tick-marks 4 --colorbar-min 15.0 --colorbar-max 35.0 --colorbar-units "°C" noaa20_viirs_sst_20231121_213000_Arabian.tif

Note the warmer temperatures during the daytime (i.e., at 0900 UTC). The difference between day and night will be especially pronounced in regions of reduced vertical mixing in the ocean (that is, light winds), and MetopB ASCAT winds on the 21st (below, from here) do show light winds over much of the Arabian Sea early on the 21st.

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