Shadow of partial solar eclipse

October 23rd, 2014
GOES-15 0.63 µm visible channel images

GOES-15 0.63 µm visible channel images

McIDAS images of GOES-15 (GOES-West) 0.63 µm visible channel data (above) showed the west-to-east progression of the shadow from a partial solar eclipse on 23 October 2014. The shadow was most obvious across the northern portion of the images, moving across Alaska, the Gulf of Alaska, and over western/northern Canada and the far northwestern portion of the Lower 48 States of the US.

According to EarthSky.org the point of greatest eclipse (75% coverage of the solar disk by the Moon) was near Prince of Wales Island, Nunavut, Canada at 21:44 UTC. In a sequence of before, during, and after-eclipse AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (below), a darkening of Canada’s Yukon Territory — which covered most of the center portion of the images — could be seen.

Suomi NPP VIIRS 0.64 µm visible channel images

Suomi NPP VIIRS 0.64 µm visible channel images

“Blood Moon” total lunar eclipse, and a selenelion

October 8th, 2014

A “Blood Moon” total lunar eclipse occurred between 09:15 UTC and 12:34 UTC on 08 October 2014. One effect of this eclipse can be seen in a comparison of nighttime “during eclipse” and “after eclipse” Suomi NPP VIIRS 0.7 µm Day/Night Band images (above). The 11:33 UTC “during eclipse” Day/Night Band image appears somewhat dim and washed out, due to limited illumination by only red sunlight being refracted by the Earth’s atmosphere into the eclipse shadow. Less than 2 hours later, the 13:14 UTC Day/Night Band image appears much more bright with crisp cloud feature details, due to an abundance of illumination from the Full Moon.

A few hours after sunrise in North America, a portion of the Moon was captured on the GOES-13 (GOES-East) 0.63 µm visible channel image at 16:30 UTC (below). Note how the edges of the Moon appear slightly jagged, caused by the fact that it was moving (setting) behind the Earth as the GOES-13 imager instrument was scanning horizontally step-wise from north to south. In addition, at the point where the edge of the Moon meets the edge of the Earth, there is a “lensing effect” where the Earth’s atmosphere is refracting light from the Moon and creating the illusion of a curved wedge of dark space that is visible within the atmosphere.

Speaking of sunrise, an interesting aspect of this lunar eclipse was that it was a rare “selenelion”, when the rising sun in the east could be seen at the same time as the non-eclipsed portion of the setting moon in the west (Space.com article). This selenelion was captured at 12:03 UTC or 7:03 am local time by the east-looking and west-looking rooftop cameras on the Space Science and Engineering Center building (below; image captures courtesy of John Lalande, SSEC).

Shotwave Infrared Imagery can Identify Power Plant Plumes

September 30th, 2014
GOES-13 Visible Imagery (0.63 µm), 1215 through 2345 UTC, 30 September 2014 (click to animate)

GOES-13 Visible Imagery (0.63 µm), 1215 through 2345 UTC, 30 September 2014 (click to animate)

The visible imagery animation above shows stratocumulus over Wisconsin behind a strong early-season cold front. Careful examination of the animation will reveal the presence of at least three exhaust plumes from power plants over Wisconsin. Imagery from 1715 UTC, below, shows visible (0.63 µm) and infrared (3.9 µm and 10.7 µm) data (Click here for an image toggle without the Big Red Box). The plume is warmer in the 3.9 µm imagery, relative to its surroundings; the plume is cooler in the 10.7 µm imagery, relative to its surroundings (an enhanced version of the loop makes this even more evident). Why does the temperature difference exist?

Plumes appear darker — warmer — in the 3.9 µm imagery because of increased reflectivity in the plume: cloud droplets in the power plant plume are smaller and more reflective of 3.9 µm radiation than the cloud droplets in the surrounding stratocumulus field. The plume is cooler in the 10.7 µm imagery because the plume is higher in the atmosphere than the surrounding stratocumulus deck.

GOES-13 Visible Imagery and Infrared Imagery (0.63 µm, 3.9 µm and 10.7 µm), at 1715 30 September 2014.  The Red box surrounds a Power Plant Plume (click to enlarge)

GOES-13 Visible Imagery and Infrared Imagery (0.63 µm, 3.9 µm and 10.7 µm), at 1715 30 September 2014. The Red box surrounds a Power Plant Plume (click to enlarge)

Suomi NPP overflew the area at 1836 UTC, and that imagery is shown below. The higher resolution data allows a better discrimination of the small plumes over the state. As with GOES data, the shortwave infrared (3.74 µm for VIIRS) data also shows warmer conditions over the plume compared to the surrounding stratocumulus deck.

Suomi NPP Visible Imagery and Infrared Imagery (0.63 µm, 3.74 µm and 11.35 µm), at 1836 UTC 30 September 2014. (click to enlarge)

Suomi NPP Visible Imagery and Infrared Imagery (0.63 µm, 3.74 µm and 11.35 µm), at 1836 UTC 30 September 2014. (click to enlarge)

Strong early-season storm in the North Pacific

September 23rd, 2014
GOES-15 6.5 µm IR channel images (click to play animation)

GOES-15 6.5 µm IR channel images (click to play animation)

The GOES-15 6.5 µm water vapor channel imagery above showed the development and evolution of a strong mid-latitude cyclone in the eastern North Pacific Basin during the 21-23 September 2014 time period; of particular interest was the development of strong subsidence behind the storm (depicted by brighter shades of yellow), and also a second jet starting to approach the storm from the west (as evidenced by increasing cold cloud tops in the base of the trough at the end of the animation). A closer view of the storm using AWIPS II imagery is available here. The strong storm had access to abundant sub-tropical moisture, as depicted in the MIMIC Total Precipitable Water animation below.

MIMIC Total Precipitable Water (click to enlarge)

MIMIC Total Precipitable Water (click to enlarge)

The ASCAT Scatterometer that flies on METOP gives routine observations of surface winds over the ocean. A large area of storm-force winds (in red) was depicted in the image below (from 0630 UTC on 23 September), overlain on the GOES-15 Water Vapor imagery.

 GOES-15 6.5 µm water vapor channel image and ASCAT winds, 0630 UTC on 23 September (click to enlarge)

GOES-15 6.5 µm water vapor channel image and ASCAT winds, 0630 UTC on 23 September (click to enlarge)

A comparison of 4-km resolution GOES-15 6.5 µm and 1-km resolution Aqua MODIS 6.7 µm water vapor channel images at 11:30 UTC, below, demonstrated the benefit of higher spatial resolution for providing a more accurate display of the water vapor gradients and various small-scale features (such as transverse banding associated with cold clouds to the north of the storm), along with the polar-orbiter image elimination of geostationary parallax error for more more precise feature location.

GOES-15 6.5 µm and Aqua MODIS 6.7 µm water vapor channel images

GOES-15 6.5 µm and Aqua MODIS 6.7 µm water vapor channel images

The GOES sounder Total Column Ozone product, below, showed an increase in ozone values (350-380 Dobson Units, darker green to lighter green color enhancement) as the tropopause was lowered in the vicinity of the deepening mid-latitude cyclone.

GOES sounder Total Column Ozone product (click to play animation)

GOES sounder Total Column Ozone product (click to play animation)

A Suomi NPP VIIRS true-color image from the SSEC RealEarth web map server, below, provided a good view of the lower-level clouds associated with the storm.

Suomi NPP VIIRS true-color image

Suomi NPP VIIRS true-color image

For a more detailed analysis of this event from the Ocean Prediction Center perspective, see the Satellite Liaison Blog.