MODIS 6.7 µm and GOES-12 6.5 µm "water vapor channel" images

AWIPS images of the 1-km resolution MODIS 6.5 µm and the 4-km resolution GOES-12 6.5 µm “water vapor channel” images (above) demonstrate the advantage of better spatial resolution for the detection of small-scale features such as the mountain waves that had formed over much of New Mexico and the adjacent states on 08 May 2009. A small amount of parallax shift is also evident on the GOES-12 image, with the features being displaced slightly to the northwest.

The presence of mountain waves implies the potential for turbulence (especially when the wave patterns interfere, as they do in this particular case) — however, very few aircraft were flying in the area at that hour, and there was only one pilot report of light turbulence at 36,000 feet near the Arizona/New Mexico border.

MODIS water vapor image + pilot reports

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GOES-12 visible images

GOES-12 visible channel images (above) showed advection fog that developed over Lake Michigan during the day on 07 May 2009. As pointed out on the US Air Quality (aka The Smog Blog) site,  this fog “fooled” the MODIS Aerosol Optical Depth (AOD) algorithm, causing a false signal of very high AOD over Lake Michigan. Also note the appearance of “shock waves” in the fog bank as it encountered obstructions to the southwesterly boundary layer flow in two areas: (1) along the western coastline of Lower Michigan (250-m resolution MODIS true color image), and (2)  some of the larger islands in the northern portion of Lake Michigan (250-m resolution MODIS true color image).

This fog formed as warm and relatively humid air (with dew points in the middle 50s F) moved across the cold waters of Lake Michigan. An AWIPS image of the MODIS Sea Surface Temperature (SST) product (below) indicated that that mid-lake SST values were still in the 37-39º F range — and  this was confirmed by the water temperature values of 37º F and 38º F reported by buoys 45002 and 45007, respectively.

MODIS Sea Surface Temperature product

The western portion of the advection fog feature was quite thin, so the fog edge was difficult to pick out on the MODIS 11.0 µm “IR window” imagery (below). However, the fog boundaries were quite apparent on the 3.7 µm “shortwave IR” imagery, due to the reflection of solar radiation off the top of the water droplet fog feature (which made the fog appear darker/warmer).

MODIS visible, 11.0 µm IR window, 3.7 µm shortwave IR images

The GOES sounder Cloud Top Height product (below) indicated that the tops of the fog feature over the southern half of Lake Michigan were generally around 2580 feet (darker brown color enhancement).

GOES-12 sounder Cloud Top Height product

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GOES-11 visible images

GOES-11 was placed into Super Rapid Scan Operations (SRSO) on 05 May 2009, as a test for support of the upcoming VORTEX2 field experiment. During SRSO, images are available at 1-minute intervals for short periods of time. The GOES-11 visible channel imagery (above) shows severe convection in southwestern Nebraska, which produced hail up to 1.25 inch in diameter (SPC storm reports).

SPC storm reports

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MIMIC Total Precipitable Water

AWIPS images of the MIMIC Total Precipitable Water (TPW) product (above) showed the presence of  long, narrow  filaments of moisture (often described as “atmospheric rivers“) that were moving across the North Pacific Ocean and the North Atlantic Ocean during the 04 May – 05 May 2009 period. Studies by Newell and others suggest that these atmospheric rivers can persist for more than 10 days, and are capable of transporting as much water as the Amazon River!
Composite geostationary satellite water vapor imagery (below) showed a similar signature of enhanced clouds and moisture along the axis these two atmospheric rivers — however, the presentation on the water vapor imagery was a bit different in terms of width and location.

MIMIC TPW + surface analysis

Note that the surface frontal structure was more closely aligned with the atmospheric rivers seen on the TPW imagery (above), but there was more of a mismatch with the corresponding water vapor image features (below). This is due to the fact that the water vapor imagery is generally sensing a signal from moisture located within a fairly deep layer aloft in the middle to upper troposphere, at a level above which the bulk of the total column precipitable water is located.

Composite water vapor imagery + surface analysis

A 4-panel comparison of the MIMIC TPW, the Blended TPW, GOES Imager water vapor channel, and the GOES Sounder TPW products (below) shows that there is good agreement to the general magnitude of the TPW values between the various products. An animation shows the various strengths and weaknesses of each in terms of their utility for tracking atmospheric rivers. The MIMIC and Blended TPW products (top 2 panels) had better  temporal continuity, while the GOES water vapor imagery and the GOES Sounder TPW product (bottom 2 panels) suffered from gaps in coverage due to either Spring eclipse or the variable GOES Sounder scanning strategy.

Comparison of MIMIC TPW, Blended TPW, GOES Imager water vapor.  and GOES Sounder TPW imagery

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