Great Lakes Surface Temperatures in GOES-16 Level 2 Products

March 19th, 2018 |

GOES-16 Level 2 Sea Surface Temperature product with Default Enhancement, re-scaled enhancement, and re-scaled enhancement with GOES-16 ABI 0.64 µm visible imagery, 1502 UTC on 19 March 2018 (Click to enlarge)

One of the Level-2 products in AWIPS is Sea-Surface Temperature.  This is created hourly on the Full Disk scale, and is shown above.   The image above toggles between the default enhancement (from -5º to 40º Celsius) to one that is more appropriate for mid-March (-5º to 30º Celsius), and then with the ABI Band 2 (0.64 µm) Visible Image.  This allow change allows for features in the Gulf of Mexico to become more obvious. (Note: The default Sea-Surface Temperature enhancement in AWIPS will change in the future; the maximum value will be 35º C, not 40º).

Sea-Surface temperatures over the Great Lakes, under clear skies, are not displayed. Sea-Surface temperatures are currently computed only over the oceans — not over large lakes.

GOES-16 Land Surface Temperature, computed hourly in the CONUS domain, does include Great Lakes water temperatures; it is shown below (Here is it in a toggle with different ABI Channels). The default temperature scale for Land Surface Temperature is -10º to 110º (Fahrenheit), which is different than the default for Sea-Surface Temperatures. The cold mid-March temperatures (low to mid-30s, generally, with a few sub-30s showing over ice) of the Great Lakes stand out plainly. Regions of ice do persist over the Great Lakes, as is apparent in this toggle between ABI’s Visible (Band 2, 0.64 µm), Snow/Ice Near-Infrared (Band 5, 1.61 µm) and Cirrus Near-Infrared (Band 4, 1.37 µm) Imagery at 1502 UTC.    Lake ice remains over eastern Lake Erie, eastern and northern Lake Superior, and north of Manitoulin Island in Lake Huron.

GOES-16 Land Surface Temperature (including SSTs where skies are clear over the Great Lakes), 1502 UTC on 19 March 2018 (Click to enlarge)

(Note: Plans exist to include large lake surface temperatures in the computation of Sea-Surface temperature at some point in the future.)

Using GLM data to monitor convective development

March 15th, 2018 |

GOES-16 Band 13 (10.3) “Clean Window” Infrared Imagery, 0815-1400 UTC, and GLM Group Density.

Strong convection developed on 15 March over the Pampas of Argentina and Uruguay, as shown above. Full Disk imagery is available only every 15 minutes, and considerable convective development is possible during the 15 minutes between scans. If a Mesoscale sector with 1-minute imagery is not over convection, Geostationary Lightning Mapper (GLM) data from GOES-16 can be used to monitor convection during the time interval between Full Disk Scans: GLM updates every minute. The 18-minute animation below (from Real Earth) includes 3 Full-Disk images and every-minute updates of GLM Group Density. Group Density between 0700-0715 shows no sign of diminishing.  It should not surprise that cloud-tops continue to expand and cool when the 0715 UTC ABI Imagery appears at the end of the loop.

Note:  When GOES-16 or GOES-17 (GOES-S achieved Geostationary Orbit on 12 March and became GOES-17) are operating under Mode 6 (vs. the present-day Mode 3), Full Disk imagery will be available every ten minutes vs. current fifteen minutes.

GOES-16 Band 13 (10.3) “Clean Window” Infrared Imagery, and GLM Group Density 0658-0717 UTC.

Moisture Changes as viewed in the Cirrus Channel

March 14th, 2018 |

GOES-16 ABI Band 3 (0.86 µm) Reflectance, hourly from 1632-1932 UTC on 14 March 2018 (Click to enlarge)

Skies were clear over much of the southern Plains on 14 March 2018, as noted in the animation above that shows hourly GOES-16 ABI Channel 3 (0.86 µm) Imagery. Differences in absorption/reflectance between water and land yield excellent discrimination between lakes and land over Oklahoma and adjacent states.  GOES-16 ABI “Cirrus Channel” (Band 4, at 1.38 µm) shows little reflectance in the area over Oklahoma, except where cirrus clouds are present over western Oklahoma.  The rest of Oklahoma is dark because water vapor in the atmosphere is absorbing energy at 1.38 µm. An animation — also at hourly intervals — is shown below.  This uses the default enhancement in AWIPS, with reflectance values between 0 and 50 shown.

GOES-16 ABI Band 4 (1.37 µm) Reflectance, hourly from 1632-1932 UTC on 14 March 2018 with default AWIPS Enhancement (Click to enlarge)

If you alter the Band 4 enhancement to change the bounds from 0-50 (the default) to 0-2 (!), as was done in the animation below showing data every 5 minutes, a gradient in reflectance becomes apparent, and surface features — specifically lakes — over central Oklahoma that are initially present slowly become obscured as the gradient moves to the east. This gradient shows differences in moisture. The atmosphere that is moving into eastern Oklahoma from central Oklahoma is slightly more moist.  (Compare the morning sounding at Amarillo, for example, with a total precipitable water of 0.38″ to the morning sounding at Little Rock, with a total precipitable Water of 0.14″)

GOES-16 ABI Band 4 (1.37 µm) Reflectance, from 1632-1947 UTC on 14 March 2018 with default AWIPS Enhancement modified as described in text (Click to animate)

GOES-16 data includes channel differences and level 2 products that also confirm the slow increase in moisture. The Split Window Difference field, shown below with the default enhancement (Click here to see the same animation with the Grid MidRange Enhanced enhancement), and the Total Precipitable Water, at bottom, show a slow increase in moisture. These increases were above the surface: surface dewpoints in this region (source) were not increasing greatly.

Split Window Difference (10.3 µm – 12.3 µm) from 1632 – 1947 UTC on 14 March (Click to enlarge)

GOES-16 Total Precipitable Water Baseline Product, 1632-1947 UTC on 14 March 2018 (Click to enlarge)

Silt at the mouth of the Mississippi River

March 13th, 2018 |

CIMSS Natural True Color Imagery, 1515 – 1830 UTC on 13 March 2018 (Click to animate)

The CIMSS Natural True Color RGB, above, from 13 March 2018, shows the motion of alluvial sediment in the Gulf of Mexico in the outflow from various rivers. Muddy plumes from the Atchafalaya River in central Louisiana, the Mississippi River, and the Mobile River in Alabama are apparent. In particular, there is distinct northward motion during the 3 hours shown in this animation along the northern edge of the Mississippi River Delta.

A similar animation for 9 March 2018 is available here (courtesy Tim Schmit, NOAA and Mat Gunshor, CIMSS). Close monitoring of where the outflow from rivers is mixing with the Gulf of Mexico waters is a capability of GOES-16 Imagery when skies are clear.

Natural True Color is computed from GOES-16 Reflectance imagery using the “Blue” band (0.47 µm), the “Red” band (0.64 µm) and the “Veggie” band (0.86 µm), that latter being used to give information that in True Color Imagery from MODIS or Suomi NPP (for example) is supplied by a true “Green” band (0.55 µm).

The animation below shows True-Color imagery from MODIS for clear days between 30 January and 13 March 2018. The superior resolution of MODIS (on the Terra and Aqua spacecraft) and the presence of a 0.55 µm channel (in addition to 0.47 µm and 0.64 µm) allows for crisper imagery than from GOES-16; however, the ability to animate at small time scales over the Gulf of Mexico is a capability reserved for GOES-16 (and GOES-17, when it becomes operational). Terra and Aqua imagery are not useful if the overpass of the Polar Orbiters coincide with clouds; on days with variable cloud cover, GOES Imagery is more likely to provide useful information.

MODIS True Color Imagery for select dates between 30 January and 13 March 2018 (Click to animate)