GOES-12 0.65 µm visible images

McIDAS images of the GOES-12 0.65 µm visible channel data (above) revealed a large hazy aerosol plume that was moving off the Northeast US and drifting out over the adjacent waters of the Atlantic Ocean on 19 March 2010. This aerosol plume exhibited Aerosol Optical Depth (AOD) values of 0.6 and higher on the GOES Aerosol/Smoke Product (GASP) on the IDEA site. Real-time GASP images are also available from the NOAA/NESDIS/SSD/OSDPD site.

A MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Direct Broadcast site (below) showed a better view of the varying structure and optical thickness of the aerosol plume.

MODIS true color Red/Green/Blue (RGB) image

An AWIPS image of the MODIS 0.65 µm visible channel data with an overlay of ECMWF 805-500 hPa layer winds (below) shows that the hazy aerosol plume was being advected eastward by a predominantly westerly flow within that layer.

MODIS 0.65 µm visible image + ECMWF 850-500 hPa layer winds

Model output from the Realtime Air Quality Modeling System (RAQMS) shows the mixing ratio of surface sulfate or SO4 (below) — this demonstrates the increase in SO4 levels over the northeastern US during the 17-19 March period, with a forecast that then advects the high levels of SO4 eastward out over the Atlantic.

RAQMS surface sulfate (SO4) mixing ratio

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Saint Patrick’s Day over the Midwest was unusually clear, affording great images of the Great Lakes from the MODIS instrument aboard the Terra and Aqua satellites. The loop above includes the Visible imagery, the cirrus detection channel (1.38 micrometers), the snow-ice detection channel (2.1 micrometers), the derived lake-surface temperatures and the normalized difference vegetation index (NDVI).

Close-up views of the individual lake basins: Ontario, Erie, Michigan-Huron and Superior show mostly uniform surface temperatures in the upper 30s (Fahrenheit) as is normal in early Spring. There are warm thermal plumes in Lake Erie, however, emerging from Sandusky Bay and from the Maumee River at Toledo. MODIS-derived Lake surface temperatures in those regions are in the upper 40s. (True-color imagery for that time (here) show great turbidity over Lake Erie; perhaps the warm temperatures are a result of enhanced run-off from the Maumee and Sandusky Rivers) Temperatures over Lake Michigan are slightly warmer in the middle of the lake — near 40 F — than along the perimeter where lake temperatures are still in the mid-30s. This might be a signature of recently melted near-shore ice.

High-resolution imagery such as these will be routinely available when GOES-R is launched and becomes the operational GOES satellite over the United States.

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GOES-13 (top) and GOES-12 (bottom) visible images

McIDAS images comparing 1-km resolution GOES-12 and GOES-13 0.65 µm visible channel data (above) revealed several smoke plumes over parts of eastern Oklahoma and western Arkansas, while the corresponding 4-km resolution GOES-12 and GOES-13 3.9 µm shortwave IR images (below) showed numerous “hot spots” (black to yellow to red pixels) due to widespread fire activity that had flared up across that region on 18 March 2010. Even though there were a number of smoke plumes seen in eastern Oklahoma, the most obvious smoke plumes (in term of size and brightness on the visible imagery) were apparent in northwestern Arkansas.

GOES-13 (top) and GOES-12 (bottom) 3.9 µm shortwave IR images

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MODIS visible and 3.7 µm shortwave IR images

AWIPS comparisons of the 1-km resolution MODIS visible and 3.7 µm shortwave IR images at 19:31 UTC (above) and the 1-km resolution AVHRR visible and 3.7 µm shortwave IR images several hours later at 23:43 UTC (below) showed that many more fire hot spots could be detected with the use of higher spatial resolution shortwave IR images (GOES vs MODIS at 19:31 UTC | GOES vs AVHRR at 23:43 UTC). The spatial resolution of the shortwave IR channels on the ABI instrument of GOES-R satellite will be 2 km, which will be an improvement over the 4 km resolution on the current GOES satellites.

AVHRR visible and 3.7 µm shortwave IR images

A closer view over northwestern Arkansas using the AVHRR visible channel, Cloud Type Product, Cloud Top Temperature, and Cloud Particle Effective Radius products at 22:03 UTC (below) showed the following: (1) the 3 large smoke plumes over northwestern Arkansas as well as the smaller cumulus clouds off the the east were composed primarily of water droplets (cyan color enhancement); (2) the Cloud Top Temperature values of the large smoke plumes were quite warm (+10 to +12º C, gray color enhancement), while some of the smaller cumulus clouds off to the east were beginning to exhibit CTT values several degrees below freezing (red to orange color enhancement); (3) the Cloud Particle Effective Radius values in the smoke plumes were significantly larger (30-40 µm, darker blue color enhancement) than those of the cumulus clouds off to the east (15-20 µm, cyan color enhancement).

AVHRR visible, Cloud Type, Cloud Top Temperature, and Cloud Particle Effective Radius

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Early morning visible imagery shows a region of modest convection developing into an arc in the Gulf of Mexico south of Louisiana. Radar imagery at 11 UTC shows a concentrated region of strong convection in the marine environment. Which satellite data can be used to identify the regions most at risk for convection in a dry environment?

Total Precipitable Water (TPW) plots (above) derived from satellite microwave data (from SSM/I on DMSP-13 and -14 and from AMSR-E on Aqua) show that the region of convective development was deep within the dry air behind a storm system moving off the southeast coast of the United States. TPWs south of Louisiana are in the 8-16 mm range. Similarly, water vapor imagery from the GOES-12 imager (below) shows predominantly dry air in the region of convective development — until the convection is actually developing. However, no precursor impulses are apparent. Unfortunately, the key development occurs during the eclipse period in the GOES-12 imagery.

Imager water vapor data includes only one channel, sensing radiation with a wavelength around 6.5 micrometers. The GOES Sounder, however, has 3 water vapor channels sensing radiation with wavelengths at 6.5, 7.0 and 7.4 micrometers (The ABI on GOES-R will also have 3 channels that detect water vapor: 6.2, 6.95 and 7.34 micrometers). The weighting functions from Lake Charles, Louisiana for 00 UTC on 18 March 2010, used in the retrieval show that only the 7.4 micrometer data should detect any significant moisture because only the curve for 7.4 micrometer shows a response function that overlaps with appreciable moisture low in the atmosphere (compare the red line in the weighting function figure to the dotted black line that represents mixing ratio). Loops are shown from the GOES-12 sounder for observed radiance at 6.5 micrometer (here), 7.0 micrometer (here), and 7.4 micrometer (here). The 6.5-micrometer loop shows information from highest in the atmosphere (and that particular channel is the noisiest), the 7.0-micrometer is for data that are somewhat lower and the 7.4-micrometer data are lower still. Only the 7.4 micrometer channel suggests an impulse upstream of where the convection eventually fired. (Note that all three animations suffer greatly from the eclipse of the satellite, that is, when the satellite (and its energy-generating solar panels) are in the Earth’s shadow. Batteries on GOES-13 through GOES-15, and on to-be-launched GOES-R will power the satellite through the eclipse.) The loop of 7.4-micrometer sounder data from just before to just after the eclipse (below), however, does show an impulse rotating towards the Gulf.

The three levels of water vapor information in the sounder can be used to produce a three dimensional distribution of moisture in the atmosphere through a sounder data retrieval. If those distributions are then transported in a Lagrangian framework by winds from a numerical model, then later distributions of moisture can be computed through the period of eclipse. (Similarly, later distributions can be computed if cloudiness develops, as the clouds restrict sounder retrievals just as much as data outages do). This method has been described in a previous CIMSS GOES blog entry and forecasts are routinely available at this CIMSS website.

Nearcast predictions of precipitable water differences between two layers (900-700 mb and 700-300 mb) show a maximum (light green color) — that is, a maximum in relatively dry air over relatively moist air, i.e., convective instability) in the region of convective development off the south-central coast of Lousiana. Because numerical models showed a middle-tropospheric vorticity center moving over this region (Click here to see the 06-h forecast valid at 0600 UTC), the region to focus on for convective development can be limited to the region off the coast of southern Louisiana.

(Added: UW Convective Initiation showed no signal for this case, likely because the active initial cloud growth occurred during the eclipse).

Because GOES-13 data were flowing 18 March 2010, a comparison of the sounder channels is possible. Below are loops for 6.5 micrometers (top) and 7.4 micrometers (bottom). Only GOES-12 data is lost during the eclipse; the GOES-13 6.5 micrometer channel is far cleaner; the impulse that gives rise to the convection is evident in the 7.4 micrometer channel (detecting lower into the atmosphere) but not in the 6.5 micrometer channel. In a dry atmosphere, information from the longer-wavelength water vapor channel on the sounder can give important clues to the movement of vapor in the lower troposphere.

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