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)

Pyrocumulonimbus clouds in Western Australia

March 1st, 2019 |

Himawari-8

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

Large bushfires burning in the southern portion of the state of Western Australia produced three pyroCumulonimbus (pyroCb) clouds on 01 March 2019. JMA Himawari-8 “Red” Visible (0.64 µm) images (above) showed that the pyroCb clouds drifted southeastward after formation.

Himawari-8 “Clean” Infrared Window (10.4 µm) images (below) further revealed the 3 distinct pyroCb pulses — 2 originating from the southernmost fire located near 29.5ºS / 124.4ºE, and a smaller one originating from a fire located farther to the northwest. Cloud-top infrared brightness temperatures cooled to the -59 to -63ºC range for the pair of larger pyroCbs (which was close to the tropopause temperature of -64ºC on Perth soundings: plot | data) with temperatures reaching -51ºC with the smaller northernmost pyroCb. Also apparent was a surge of cooler air moving northeastward behind a surface trough, whose arrival appeared to coincide with the pyroCb formation. A time series of surface data from Forrest (YFRT) clearly showed the arrival of the cool, moist air behind the trough.

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

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

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0537 UTC [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0537 UTC [click to enlarge]

As shown using RealEarth, an overpass of the Suomi NPP satellite provided a more detailed view of the first (and largest) pyroCb at 0537 UTC (above), with NOAA-20 capturing the second pyroCb cloud about an hour later at 0628 UTC (below). The coldest cloud-top infrared brightness temperature on the 0537 UTC Suomi NPP VIIRS image was -70ºC (darker black enhancement); in addition, there appeared to be an Above-Anvil Cirrus Plume associated with that pyroCb, extending southeastward from a subtle Enhanced-V signature at the upshear (northwestern) edge of the cloud (where the warmest temperature was -48ºC, green enhancement).

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0628 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0628 UTC [click to enlarge]

On Himawari-8 Shortwave Infrared (3.9 µm) images (below), the pyroCb clouds exhibited a warmer (darker gray) appearance compared to adjacent conventional cumulonimbus clouds — this is due to the fact that ice crystals ejected into the pyroCb anvils are smaller (due to their shorter residence time within the intense updrafts above the fires), and these smaller ice crystals are more effective reflectors of incoming solar radiation. The large flare-up of red-enhanced land during the day is due to highly reflective soils of the Great Victoria Desert that quickly become very hot.

Himawari-8 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

Himawari-8 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

Standing wave west of Tropical Cyclone Pola in the South Pacific

February 26th, 2019 |

Himawari-8 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

Himawari-8 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

Himawari-8 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed an interesting standing wave west/northwest of Tropical Cyclone Pola in the South Pacific Ocean on 26 February 2019. The long-lived wave first became apparent just before 0800 UTC, and persisted until about 2330 UTC.

The standing wave feature was also apparent in Himawari-8 “Clean” Infrared Window (10.4 µm) images (below). The abrupt warming of cloud-top infrared brightness temperatures associated with the wave suggests that subsidence was lowering the cloud height. Also note the very cold cloud-top temperatures of -90ºC and colder (yellow pixels embedded within the darker purple enhancement) — this was colder than the tropopause temperature on 12 UTC rawinsonde data from both Nadi, Fiji (NFFN) to the southwest and Pago Pago, American Samoa (NSTU) to the northeast (the wave feature was located closer to the Nadi sounding).

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

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

Consecutive VIIRS Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20, as viewed using RealEarth (below) showed a definitive bore-like structure with the wave, especially along the northern end.

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

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

Himawari-8 “Red” Visible (0.64 µm) images (below) showed the feature during daylight hours — a distinct shadow was being cast during local sunrise, which indicated a sharp drop-off in cloud height from east to west along the wave.

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]

A HWRF-P model sounding for the latitude/longitude point 15.42ºS/179.75ºW valid at 18 UTC (source) showed directional wind shear at the 450 hPa pressure level — such a wind shear could have acted to initiate a horizontal roll circulation, creating a narrow zone of cloud-eroding subsidence. In addition, a sharp change in wind direction was seen above 150 hPa on the Paga Pago sounding — and the Nadi sounding showed speed shear with height — which also could have induced a horizontal roll circulation within the upper troposphere.

HWRF-P model sounding for the location 15.42ºS 179.75ºW at 18 UTC [click to enlarge]

HWRF-P model sounding for the location 15.42ºS/179.75ºW at 18 UTC [click to enlarge]

An interesting phenomenon was the apparent “shedding” of high-altitude cloud material from the higher/colder cloud canopy of Pola immediately east of the wave feature, as seen in Himawari-8 Shortwave Infrared (3.9 µm) images (below). The westward direction and velocity of this cloud material motion had good agreement with GFS model winds at 150 hPa. Note that this shed cloud material appeared warmer (darker gray) in the 3.9 µm imagery — the shearing of cirrus cloud may have acted to fracture the ice crystals, making them smaller in size and therefore more efficient reflectors of incoming solar radiation.

Himawari-8 Shortwave Infrared (3.9 µm) images, with plots of GFS 150 hPa winds [click to play animation | MP4]

Himawari-8 Shortwave Infrared (3.9 µm) images, with plots of GFS 150 hPa winds [click to play animation | MP4]

A toggle between GOES-17 (GOES-West) Infrared and Water Vapor images from the CIMSS Tropical Cyclones site (below) showed that the feature was aligned with a couplet of low-level convergence and upper-level divergence at 15 UTC — such an environment could also support a vertically-propagating gravity wave.

GOES-17 Infrared and Water Vapor images, with contours of low-level convergence and upper-level divergence at 15 UTC [click to enlarge]

GOES-17 Infrared and Water Vapor images, with contours of low-level convergence and upper-level divergence at 15 UTC [click to enlarge]

Another analysis of this feature is available from the Australian Bureau of Meteorology Training Centre.