GOES Sounder Imagery during Filter Wheel Anomaly

On June 20, 2012, the GOES-13 Sounder Filter Wheel mechanism suffered an anomaly. The filter wheel moves the spectral filters into the optical path of sensed radiation. As a result of the anomaly, data quality was degraded starting at about 1248 UTC. Instrument recovery activities occurred at 1756 UTC on 20 June, and qualitatively the data returned to normal. Imager data were not affected.

GOES Sounder Imagery during Filter Wheel Anomaly

When GOES Sounder data are degraded, GOES Sounder Derived Product Imagery is also degraded. For example, the Precipitable Water image from 1746 UTC on June 20 is shown above. GOES-15 Sounder data returns over the western United States do not show the data dropouts characterized by the Filter Wheel Anomalies in GOES-13 over the eastern United States.

Filter Wheel anomalies have occurred in the past on GOES-12. GOES-10 Filter Wheel anomalies caused a data interruption on GOES-10 from Oct 14th to Nov 6th, 2008. GOES-8 also suffered from rare filter wheel anomaly issues (Link).

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WMS Image of Tropical Storm Chris and SSTs

The image above from the SSEC Web Map Service (WMS) shows visible imagery of Tropical Storm Chris over the central Atlantic on June 20th, just south of the north wall of the Gulf Stream. Sea-surface temperatures are indicated by the color shading. The projected path of the storm, and the cone of uncertainty (retrieved from the NOAA nowcoast wms), are also indicated. The path takes the storm over the cold waters of the North Atlantic, so strengthening to hurricane status is unlikely, especially after today. (Added: Click here for QuickTime animation of WMS images)

For more information on Chris, please see the National Hurricane Center website, or the CIMSS Tropical Cyclones website.

===== 21 June Update =====

GOES-13 10.7 µm IR channel images (click image to play animation)

Chris did manage to reach hurricane intensity for several hours on 21 June 2012 (NHC advisory), becoming the first hurricane of the 2012 North Atlantic season.  GOES-13 10.7 µm IR channel images (above; click image to play animation) showed a well-defined eye during this period.

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MODIS volcanic ash mass loading, ash height, and ash effective radius products

According to the Alaska Volcano Observatory, the Mount Cleveland volcano erupted around 22:05 UTC on 19 June 2012 (volcanic activity notice). A comparison of AWIPS images of the MODIS volcanic ash mass loading, ash height, and ash effective radius products (above) showed the volcanic ash plume about 1 hour and 40 minutes later (23:44 UTC). The products indicated that the mass loading was as high as 5.1 tons per square km, the maximum ash height was 7.92 km, and the maximum ash effective radius was 11.95 µm.

A comparison of a 23:43 UTC POES AVHRR 0.86 µm visible image with the corresponding 12.0 µm IR image (below) showed no discernable signal of the volcanic ash plume.

POES AVHRR 0.86 µm visible channel image + 12.0 µm IR channel image

A 375-meter resolution Suomi NPP VIIRS 3.74 µm shortwave IR image (below) revealed a “hot spot” (yellow to red color enhancement) associated with the Mount Cleveland volcanic eruption. The maximum IR brightness temerature within the volcanic hot spot was 337.46 K or 64.31º C.

Suomi NPP VIIRS 3.74 µm shortwave IR image

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MODIS 0.65 µm visible channel image + Land Surface Temperature product

The daily maximum temperature reported by the cooperative observer at Death Valley, California was 119 F on 17 June 2012, which was the highest temperature in the Lower 48 states so far in the summer season. A comparison of AWIPS images of 1-km resolution MODIS 0.65 µm visible channel data with the corresponding Land Surface Temperature (LST) product (above) showed LST values as high as 150 F (darker red color enhancement) in some parts of Death Valley (which is located just east of the Superior Valley Gunnery Range, station identifier K4SU). While there is not a direct 1:1 correspondence between LST and the air temperature measured by a thermometer in a standard instrument shelter at a height of 5 feet off the ground, the LST product can still be useful in terms of locating important temperature gradients or identifying which areas of a particular county might be the warmest or the coldest.

A 250-meter resolution MODIS true color Red/Blue/Green (RGB) image from the SSEC MODIS Today site (below) showed that some patches of snow cover still remained at the highest elevations of the Sierra Nevada mountain range. A wide range in surface air temperatures was seen across the region, dependent on elevation: morning low temperatures at high elevation sites included 42 F at Tuolumne Meadows and 46 F at Lodgepole in California, and 45 F at Mt. Charleston, NV.

MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

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