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!

Wildfires on the Korean Peninsula

April 4th, 2019 |

JMA Himawari-8 Shortwave Infrared (3.9 µm) images, with plots of surface reports (metric units) [click to play animation | MP4]

JMA Himawari-8 Shortwave Infrared (3.9 µm) images, with hourly plots of surface reports in metric units [click to play animation | MP4]

2.5-minute rapid scan JMA Himawari-8 Shortwave Infrared (3.9 µm) images (above) showed numerous thermal anomaly (or “hot spot”, darker red to black pixels) signatures of wildfires across southeastern North Korea and northeastern South Korea on 04 April 2019 (media story). The fires were fanned by strong west-southwest winds in the wake of a cold frontal passage associated with an anomalously-deep midlatitude cyclone moving across far northeastern China (surface analyses); winds gusted to 53 knots at Yangyang International Airport (station identifier RKNY) to the south of Sokcho at 09 UTC (below). Standing wave clouds — forming in response to the strong westerly winds — were seen downwind of the mountainous terrain of the eastern Korean Peninsula from 1030-1930 UTC.

Time series of surface weather data at Yangyang, South Korea [click to enlarge]

Time series of surface weather data at Yangyang, South Korea [click to enlarge]

Comparisons of VIIRS Day/Night Band (0.7 µm), Near-infrared (1.61 µm and 2.25 µm), Shortwave Infrared (3.75 µm and 4.05 µm) and Infrared Window (11.45 µm) images from NOAA-20 at 1649 UTC and Suomi NPP at 1739 UTC are shown below (courtesy of William Straka, CIMSS). A subtle thermal signature of the largest fires — located between Gangneug and Donghae, and also near Sokcho — was even apparent as darker pixels on the Infrared Window (I-Band 5, 11.45 µm) images. On the Day/Night Band images, note the striking lack of city lights in the southeastern portion of North Korea in these nighttime scenes.

NOAA-20 VIIRS Day/Night Band (0.7 µm), Near-infrared (1.61 µm and 2.24 µm), Shortwave Infrared (3.75 µm and 4.05 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm), Near-infrared (1.61 µm and 2.25 µm), Shortwave Infrared (3.75 µm and 4.05 µm) and Infrared Window (11.45 µm) images at 1649 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), Near-infrared (1.61 µm and 2.24 µm), Shortwave Infrared (3.75 µm and 4.05 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), Near-infrared (1.61 µm and 2.25 µm), Shortwave Infrared (3.75 µm and 4.05 µm) and Infrared Window (11.45 µm) images at 1739 UTC [click to enlarge]

Thermal signatures of the fires were also captured by KMA COMS-1 Shortwave Infrared (3.9 µm) imagery (below), but not as well as with Himawari-8 given the inferior spatial resolution (4 km, vs 2 km for Himawari-8) and image frequency (15 minutes, vs 2.5 minutes with the Himawari-8 Japan Sector).

KMA COMS-1 Shortwave Infrared (3.9 µm) images, with hourly plots of surface reports in metric units [click to play animation | MP4]

KMA COMS-1 Shortwave Infrared (3.9 µm) images, with hourly plots of surface reports in metric units [click to play animation | MP4]

Tropical Cyclone Veronica north of Australia

March 21st, 2019 |

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (1145 µm) images at 1716 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1716 UTC [click to enlarge]

A toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (above) showed Category 4 Cyclone Veronica off the northern coast of Western Australia at 1716 UTC on 21 March 2019. Ample illumination from a Full Moon maximized the “visible image at night” capability of the Day/Night Band.

In a comparison of Microwave images from Suomi NPP ATMS at 1716 UTC and from GCOM-W1 AMSR2 at 1732 UTC (below), an eyewall that was nearly completely closed was apparent. Suomi NPP and GCOM-W1 images courtesy of William Straka, CIMSS.

Microwave images from Suomi NPP ATMS at 1716 UTC and from GCOM-W1 AMSR2 at 1732 UTC [click to enlarge]

Microwave images from Suomi NPP ATMS at 1716 UTC and from GCOM-W1 AMSR2 at 1732 UTC [click to enlarge]

A DMSP-17 SSMIS Microwave (85 GHz) image at 2246 UTC from the CIMSS Tropical Cyclones site is shown below. The deep-layer Wind Shear at 21 UTC was low (green contours), and Sea Surface Temperature values were quite high — both factors favorable for continued intensification as Veronica moved slowly toward the coast.

DMSP-17 SSMIS Microwave (85 GHz) image at 2246 UTC, with an overlay of 21 UTC deep-layer Wind Shear, and Sea Surface Temperature [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) image at 2246 UTC, with an overlay of 21 UTC deep-layer Wind Shear, and Sea Surface Temperature [click to enlarge]

2.5-minute interval rapid scan Himawari-8 Infrared Window (10.4 µm) images (below) showed increasing organization to the eyewall structure. At times the cloud-top infrared brightness temperatures were -90ºC and colder (yellow pixels embedded within darker purple). Note: the rapid scan sector was re-poositioned eastward at 0100 UTC (to monitor Cyclone Trevor), so 10-minute imaging resumed after that time.

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

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

After sunrise, rapid scan Himawari-8 “Red” Visible (0.64 µm) images (below) revealed that the large eye was completely cloud-filled.

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

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

Adventures with geo2grid: Creating Stereoscopic Imagery in True Color

March 14th, 2019 |

GOES-17 True Color (left) and Himawari-8 True Color (right) at 0330 UTC on 13 March 2019 (Click to enlarge).

Geo2grid is a python-based software package that creates GeoTIFF imagery from native Himawari or GOES-16/GOES-17 imagery, as noted here. This blog post documents how to use the geo2grid software to create stereoscopic imagery, using either a Himawari-8/GOES-17 pairing, or a GOES-16/GOES-17 pairing. This requires first a remapping of the imagery to a fixed domain; when Geostationary Satellites aren’t separated by a great distance — for example when GOES-17 was in the test position and GOES-16 was at 75.2 — native projections can be used. That’s not the case with Satellites separated by 60 degrees of longitude.

Fortunately, geo2grid allows for a way to define a grid onto which the extracted data will be placed. The shell script command to create the map parameters is shown below:

$GEO2GRID_HOME/bin/p2g_grid_helper.sh G17H8Stereo -175.0 0.0 2000 -2000 1000 1000 > $GEO2GRID_HOME/mygrids.conf

I’m creating a map called ‘G17H8Stereo’ that is centered at 175 W and the Equator (Note: if you include a decimal point, you must include a digit afterwards. Some scripting languages fail to interpret ‘-175.’ correctly). The x-direction spacing is 2000 m (i.e., 2 km) and the y-direction spacing is also 2 km (that value is negative because point 1,1 is in the northwest corner). The grid size being created here is 1000×1000. If you were to look in the file created, mygrids.conf, you’d see a line looking like this:

G17H8Stereo, proj4, +proj=eqc +datum=WGS84 +ellps=WGS84 +lat_ts=0.00000 +lon_0=-175.00000 +units=m +no_defs, 1000, 1000, 2000.00000, -2000.00000, 176.01685deg, 8.98315deg

Note that the file name must have that “.conf” extension! The reading software expects it.

Data for both times (Full Disk imagery) has been downloaded and placed in directories.  This is HSD *.DAT files for Himawari-8 and netCDF Radiance files from CLASS for GOES-17.  This is a lot of data to move around.  The geo2grid invocation to create the True Color Imagery will look something like this for Himawari-8:

$GEO2GRID_HOME/bin/geo2grid.sh -r ahi_hsd -w geotiff –grid-configs $GEO2GRID_HOME/mygrids.conf -g G17H8Stereo –method nearest -f /data-ssd/CLASS/CSPPCheck/Stereo/H8/

The GOES-17 call will look like this:

$GEO2GRID_HOME/bin/geo2grid.sh -r abi_l1b -w geotiff –grid-configs $GEO2GRID_HOME/mygrids.conf -g G17H8Stereo –method nearest -f /data-ssd/CLASS/CSPPCheck/Stereo/

In both cases, –grid-configs is used to specify the grid to be used, with the -g tag naming the grid (the same name as used in the p2g_grid_helper.sh call above. The method of interpolation (the –method flag) is nearest neighbor, so a simple interpolation is used. Again, remember that those long dashes are really two short dashes.

Geo2grid does have built-in maps that you can use, and these are listed in the on-line documentation; you would include something like “-g lcc-aus” and that would put the data on a lambert conformal grid centered over Australia (not a useful grid for GOES-17, but very nice for Himawari-8 and for the coming GEOKOMPSAT-2!)

True Color imagery is created by these geo2grid.sh calls — and imagery for all 16 bands is created as well. (You can use the -c flag in geo2grid.sh to limit what is created if you wish). That imagery is shown above. If you cross your eyes and focus on the image that appears in the middle, it will be in three dimensions. Because this region is in the middle of the ocean, geo-location might be important, and the geo2grid script add_coastlines.sh is useful to add latitude/longitude lines.


How will True Color appear in regions with land features as might occur with GOES-16 and GOES-17?  Halfway between GOES-16 (75.2) and GOES-17 (137.2) is 106 degrees W Longitude.  I’ll create a map centered at 35 N, 106 W (near Albuquerque) that is 1200×1200 (also 2 km resolution):

$GEO2GRID_HOME/bin/p2g_grid_helper.sh G16G17Stereo -106.0 35.0 2000 -2000 1200 1200

The output is placed in the same Mygrids.conf file (More than one map definition can appear in that csv file). AFter downloading the GOES16/GOES17 data, I invoked to geo2grid commands:

$GEO2GRID_HOME/bin/geo2grid.sh -r abi_l1b -w geotiff –grid-configs $GEO2GRID_HOME/mygrids.conf -g G16G17Stereo –method nearest -f /data-ssd/CLASS/CSPPCheck/Stereo/G16G17/G17/

$GEO2GRID_HOME/bin/geo2grid.sh -r abi_l1b -w geotiff –grid-configs $GEO2GRID_HOME/mygrids.conf -g G16G17Stereo –method nearest -f /data-ssd/CLASS/CSPPCheck/Stereo/G16G17/G16/

Use ImageMagick to put the images side-by-side

montage GOES-16_ABI_RadF_true_color_20190313_210036_G16G17Stereo.tif GOES-17_ABI_RadF_true_color_20190313_210038_G16G17Stereo.tif -tile 2×1 -geometry +0+0 GOES-16_GOES-17_ABI_RadF_true_color_20190313_210036_G16G17Stereo.png

The beautiful stereoscopic image below is created.

True-Color imagery from GOES-16 (Left) and GOES-17 (Right) over the western United States at 2100 UTC on 13 March 2019 (Click to enlarge)

The mp4 animation below (click here for an animated gif) shows GOES-16 True Color imagery every 15 minutes (GOES-16 was in Mode 3 operations with 15-minute full-disks) from 1500 UTC to 2245 UTC. Imagery was created using geo2grid. The true-color imagery captures the dust that was kicked up by strong winds over Texas and New Mexico.

GOES-16 True Color animation, 1500-2245 UTC on 13 March 2019 (Click to play mp4 animation)

A similar animation made from GOES-17 from geo2grid is below. (Click here for an animated gif).

GOES-17 True Color animation, 1500-2245 UTC on 13 March 2019 (Click to play mp4 animation)

The GOES-16 and GOES-17 animations are combined into a true-color stereoscopic view of the strong cyclone below. The mp4 is below; click here for an animated gif.

True-Color imagery from GOES-16 (Left) and GOES-17 (Right) over the western United States from 1500-2245 UTC on 13 March 2019 (Click to play mp4 animation)