Mountain wave signatures on water vapor imagery

March 9th, 2009 |
GOES-11 + GOES-12 water vapor imagery

Composite of GOES-11 (GOES-West) + GOES-12 (GOES-East) water vapor imagery

Strong winds over much of the southwestern US (surface winds gusted to 75 mph at Sierra Rotors Site 7 in California) were responsible for producing large areas of mountain waves across a good deal of that particular region on 09 March 2009. These mountain waves were seen on  AWIPS composite images of the 8-km resolution GOES-11 (GOES-West) 6.7 µm and the 4-km resolution GOES-12 (GOES-East) 6.5 µm water vapor channels (above) — and there were a number of pilot reports of light to moderate turbulence within the 26,000-50,000 feet layer over the southwestern US.

MODIS  + GOES water vapor imagery

MODIS + GOES-11 water vapor imagery

A comparison of the 1-km resolution MODIS 6.7 µm with the 8-km resolution GOES-11 water vapor imagery at around 18:30 UTC (above) showed a marked improvement in the ability to detect the location and areal coverage of the mountain waves.

MODIS + GOES-11/GOES-12 water vapor imagery

MODIS + GOES-11/GOES-12 water vapor imagery

A similar comparison of the the 1-km resolution MODIS 6.7 µm with a composite of the 8-km resolution GOES-11 6.7 µm (GOES-West) plus the 4-km resolution GOES-12 6.5 µm (GOES-East) water vapor images (above) demonstrated the improvement in mountain wave detection capability with the newer 4-km water vapor channel on the newer GOES-12 (and also the GOES-13) satellites — but as expected, neither are as capable as the 1-km MODIS water vapor channel in terms of displaying mountain wave signatures.

GOES-13 water vapor images

GOES-13 water vapor images

GOES-13 shares the same 4-km resolution 6.5 µm water vapor channel as GOES-12, but in this case GOES-13 had the advantage of a more direct satellite view angle (GOES-13 is positioned over the Equator at 105º W longitude). As a result, the GOES-13 water vapor imagery (above) did a very good job of depicting the areal coverage  (as well as the temporal evolution) of the mountain wave signatures. Note how some wave signatures were stationary (anchored to the terrain that caused them to form), while other wave signatures appeared to propagate downwind over time.

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 –