The Moon on GOES-13 imagery

March 9th, 2009 |
GOES-13 visible and 10.7 µm IR imag

GOES-13 visible and 10.7 µm IR images at 17:45 UTC (left) and 18:15 UTC (right)

Several times a year the Earth’s Moon is captured on geostationary satellite imagery — but the geometry has to be exactly right in order for the Moon to be seen. A comparison of GOES-13 images (above) shows the Moon at two different times on 09 March 2009 first at 17:45 UTC (left image panels) with an apparent location to the northwest of Alaska, and again 30 minutes later at 18:15 UTC (right image panels) with an apparent location to the northeast of Greenland.

Since much of the Moon was illuminated by the Sun, the surface exhibited a hot IR brightness temperature (around 331 K / 58º C / 157º F) as indicated by the bright yellow color enhancement on the IR images. The yellow/black striping on the IR images is due to the fact that the very hot lunar surface temperatures highlight the detector-to-detector responsivity differences. Also note that the shape of the moon was not round in the images, but somewhat “oblong”  — this is due to the fact that while the Moon is moving fairly quickly across the satellite field of view,  the relatively slow horizontal scanning direction of the GOES imager instrument makes the shape of the Moon appear a bit distorted.

The GOES-13 visible image of the Moon (below, courtesy of Tim Schmit, NOAA/NESDIS/STAR/ASPB) was acquired during the initial GOES-13 post-launch testing during the Summer of 2006. One of the test procedures addressed lunar calibration: the goal was to observe the Moon as soon as possible after launch of GOES-13, in order to establish a baseline for future study of GOES instrument degradation.

 

GOES-13 visible image of the Moon

GOES-13 visible image of the Moon

Here are two other examples which show the Moon on GOES-08 and GOES-12 imagery.

Blended Total Precipitable Water products

March 9th, 2009 |
Blended Total Precipitable Water (AWIPS menu)

Blended Total Precipitable Water (AWIPS menu)

Beginning on 09 March 2009, two new Blended Total Precipitable Water (TPW) products were made available to NWS forecast offices who have installed AWIPS Operational Build 9 (OB9) — a Blended TPW product (above; Animated GIF), and a Percent of Normal TPW product (below; Animated GIF).

Percent of Normal TPW (AWIPS menu)

Percent of Normal TPW (AWIPS menu)

The Blended TPW products incorporate data from a number of polar-orbiting and geostationary satellite platforms. Over water, the algorithm currently uses data from:

  • the SSM/I instrument (on the DMSP F13 satellite)
  • the AMSU instrument (on the NOAA-15, NOAA-16, NOAA-17, NOAA-18, and MetOp-A satellites)

and over land, the algorithm uses data from:

  • the  GOES Sounder instrument (on the GOES-11 and GOES-12 satellites)
  • ground-based Global Positioning System (GPS-MET) receivers

On AWIPS, the Blended TPW product is generated using the latest data source available for each pixel; it is  then  mapped to a Mercator projection with a spatial resolution of 16 km at the Equator. The products are available in AWIPS on a varying schedule, but in general there will be 1 or 2 Blended TPW images per hour.

The Percent of Normal TPW  (or “Blended TPW Anomaly”) product (below) compares the current Blended TPW values to the mean values derived during the 1988-1999 time period (using a climatology of SSM/I TPW over oceans, and a mix of rawinsonde and TOVS sounding TPW over land). Note that while the raw TPW Anomaly product is capable of calculating  values in excess of 200%, on AWIPS all of the TPW Anomaly values  greater than 200% are simply colored yellow (and displayed as “> 201” using AWIPS cursor sampling).

Blended TPW Percent of Normal (TPW Anomaly)

Percent of Normal TPW (TPW Anomaly)

A 4-panel comparison of Blended, GOES Sounder, DMSP SSM/I, and POES AMSU TPW products (below, using a different CIMSS TPW enhancement) demonstrates some of the advantages of the blended TPW product, namely (1) no gaps between the individual swaths of polar-orbiting satellite data over water, and (2) the availability of TPW data in areas of dense cloud cover (over both land and water).

Comparison on Blended, GOES Sounder, DMSP SSM/I, and POES AMSU TPW products

Comparison of Blended, GOES Sounder, SSM/I, and AMSU TPW products

A comparison of AWIPS cursor sampling of the Blended, GOES Sounder, DMSP SSM/I, and POES AMSU TPW products (below) shows that in general, the TPW value for any given location should agree to within a few millimeters (or within several hundredths to perhaps one tenth of an inch).

Comparison of Blended, GOES sounder, SSM/I, and AMSU TPW products

Comparison of Blended, GOES sounder, SSM/I, and AMSU TPW products

However, at times there may be some disagreement between TPW values at any particular point (below), due to temporal differences of the data as displayed in AWIPS. In other words, the time displayed in the AWIPS product label may not necessarily apply to all portions of the displayed image.

Comparison of Blended, GOES sounder, SSM/I, and AMSU TPW products

Comparison of Blended, GOES sounder, SSM/I, and AMSU TPW products

The images below show the coverage of the Blended TPW product when displayed in AWIPS at the Northern Hemisphere, Pacific Mercator, North America, Pacific Satellite, and CONUS scales.

Blended TPW product (displayed on the Northern Hemisphere scale)

Blended TPW product (displayed on the Northern Hemisphere scale)

Blended TPW product (displayed on the Pacific Mercator scale)

Blended TPW product (displayed on the Pacific Mercator scale)

Blended TPW product (displayed on the North America scale)

Blended TPW product (displayed on the North America scale)

Blended TPW product (displayed on the Pacific Satellite scale)

Blended TPW product (displayed on the Pacific Satellite scale)

Blended TPW product (displayed on the CONUS scale)

Blended TPW product (displayed on the CONUS scale)

The Blended TPW and TPW Anomaly products were developed at the Cooperative Institute for Research in the Atmosphere (CIRA), and over the past few years they have been transitioned from research into NESDIS operations.

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References and related websites:

  • Kidder, S.Q. and A.S. Jones, 2007: A blended satellite Total Precipitable Water product for operational forecasting.
  • Ferraro et al., 2005: NOAA Operational Hydrological Products Derived From the Advanced Microwave Sounding Unit. IEEE Trans. Geosci. Remote Sens., 43, 1036-1049.
  • Alishouse, J.C., S. Snyder, J. Vongsathorn, and R.R. Ferraro, 1990: Determination of oceanic total precipitable water from the SSM/I. IEEE Trans. Geo. Rem. Sens., Vol. 28, 811-816.
  • Smith et al., 2007: Short-Range Forecast Impact from Assimilation of GPS-IPW Observations into the Rapid Update Cycle. Mon. Wea. Rev., 135, 2914-2930.
  • Schmit et al., 2002: Validation and use of GOES Sounder moisture information. Wea. Forecasting, 17, 139-154.

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updated 20 March 2009 –

Ship track plumes over the Gulf of Alaska

March 4th, 2009 |
GOES-11 visible images

GOES-11 visible images

An impressive display of “ship track” plumes was seen on GOES-11 visible images (above; also available as a QuickTime animation) over the Gulf of Alaska on 04 March 2009. Most of the ships in that region were traveling in a westward or a northwestward direction, but you can also see a handful of ships that were moving fairly quickly toward the northeast.

The corresponding GOES-11 3.9 µm shortwave IR images (below; also available as a QuickTime animation) confirm that these features are indeed ship tracks — the solar reflection of the ship track plumes (which were composed of rather small water droplets) caused an increasingly “warm signal” (darker gray enhancement) to appear as long as the sun angle was high. Note how this “dark/warm signal” was absent at the beginning and at the end of the animation, when the sun angle was low in the early morning and in the early evening hours.

GOES-11 3.9 µm shortwave IR images

GOES-11 3.9 µm shortwave IR images

A 1-km resolution NOAA-17 AVHRR visible image provides a closer view of the ship tracks (below).

NOAA-17 AVHRR visible image

NOAA-17 AVHRR visible image

Using McIDAS to track the motion of the leading edges of 4 of    the northweastward-moving ship tracks yielded forward ship speeds of 15-25 knots (below, courtesy of Rick Kohrs, SSEC).

GOES-11 3.9 µm shortwave IR + ship track speed/direction vectors

GOES-11 3.9 µm shortwave IR + ship track speed/direction vectors

GOES visible images + GOES satellite-derived winds

GOES visible images + GOES satellite-derived winds

AWIPS images of the GOES visible channel with an overlay of GOES-derived satellite winds (above; also available as a QuickTime animation) displayed a number of wind vectors in the region of the ship track plumes, but all the winds in that particular area were assigned heights within the 775-600 hPa layer. The height assignments for these winds seem a bit too high though, given that studies such as  Durkee et al (2000) found that most ship tracks formed in marine boundary layers that were between 300 and 750 m deep. Nearly all of the satellite winds in the ship track region were derived using the GOES visible channel.

An AWIPS image of the ASCAT scatterometer winds (below) confirmed that the surface winds were turning anticyclonically over the region where many of the ship tracks were exhibiting a strongly-curved appearance (before higher clouds moved overhead and obscured their view). The speeds of the ASCAT winds were similar to those of the GOES winds (generally 10-15 knots).

GOES-11 visible image + geostationary satellite and ASCAT winds

GOES-11 visible image + geostationary satellite and ASCAT winds

Lake Michigan lake-effect snow band, and Lake Superior ice

March 2nd, 2009 |
GOES-13 visible images

GOES-13 visible images

A single-band lake-effect snow event dropped as much as 14.4 inches of snow in parts of Milwaukee, Wisconsin on 02 March 2009. GOES-13 visible images (above) showed the narrow but intense band as it meandered across the far western portion of Lake Michigan.

GOES-12 sounder visible images with an overlay of GOES-12 imager-derived CIMSS Mesoscale Winds (below) indicated that there was some low-level convergence helping to establish and maintain the band.

GOES-12 sounder visible images + GOES-12 mesoscale winds

GOES-12 sounder visible images + GOES-12 CIMSS Mesoscale Winds

A comparison of 250-meter resolution MODIS “true color” and “false color” images (below) showed a number of interesting features that were not as apparent on the GOES imagery above: (1) there were several narrow bands of snow cover (snow on the ground shows up as cyan-colored features on the false color image) along the southern part of Lake Michigan (from a lake-effect snow band event on the previous day); (2) intricate structure to the ice floes in the southeastern part of Lake Michigan; (3) some of the lakes in southern Wisconsin were showing more of a darker blue signature, indicating that the ice had lost it’s top layer of snow cover.

MODIS 250-m resolution true-color and false-color images

MODIS 250-m resolution “true color” and “false color” images

Farther to the north, several days of cold temperatures (overnight lows in the -20s to -30s F, with -31º F or -35º C at both Spincich Lake in Upper Michigan and Land O’ Lakes in northern Wisconsin on the morning of 02 March) led to a significant increase in ice coverage over Lake Superior. GOES-13 visible images (below) showed the extent of the ice, which was not moving a great deal during the day due to fairly light winds. It was interesting to note that 2 separate lake vortices tried to form over Lake Superior, but the light winds and the thick ice conspired to prevent them from becoming well organized.

GOES-13 visible images

GOES-13 visible images