Google Earth Imagery from SSEC

December 17th, 2007 |

AVHRR imagery in Google Earth (Animated GIF)

Two new sources of Google Earth satellite imagery are now available from SSEC: AVHRR images from the NOAA operational polar orbiting satellites, and MODIS images from the NASA Terra and Aqua satellites. An example of the AVHRR “false color” imagery (above) zooms in to show the deep snow cover that existed over much of the Upper Midwest on 17 December 2007. Note the darker appearance of the Chicago IL and Milwaukee WI metro areas; even though those cities had a significant amount of snow on the ground, the higher concentration of trees, buildings, and paved surfaces all contributed to a somewhat “darker” satellite scene in those urban areas (compared to the adjacent outlying rural areas). Also evident on the AVHRR image were well-defined lake-effect snow bands over Lake Michigan that were moving inland over portions of Michigan and Indiana — these snow bands were on the far western periphery of a large winter storm that was centered over the Northeast US.

MODIS Google Earth imagery

MODIS “true color” imagery from the MODIS Today site (above) revealed a large number of lake-effect snow (LES) bands over parts of Lake Superior, Lake Michigan, and Lake Huron as cold arctic air streamed southward across the Great Lakes on 14 December 2007; these LES bands produced 3-6 inches of snowfall at some locations in the Upper Peninsula of Michigan. On that same day, MODIS imagery farther to the east showed a variety of banded cloud features over the Mid-Atlantic states (below).

MODIS Google Earth imagery

Snow vs stratus cloud discrimination

December 17th, 2007 |

MODIS visible + snow/ice channel images (Animated GIF)

AWIPS images of the MODIS visible and 1.6 µm “snow/ice channel” images from 17 December 2007 (above) demonstrate the utility of the snow/ice channel for helping to identify areas of thin supercooled water droplet stratus clouds that exist over a snow-covered satellite scene (this MODIS imagery was mentioned in the NWS Milwaukee/Sullivan Area Forecast Discussion that afternoon). Note the semi-transparent nature of many of the stratus cloud patches, which allowed surface features (such as rivers, cities, and densely-forested areas) to be seen on the visible image.

The GOES-12 sounder Cloud Top Height product (below) suggested that the tops of the thicker stratus cloud areas located over northern Wisconsin and northern Illinois were 9000-9800 feet above ground level (yellow enhancement). Surface METAR data under those same cloud features indicated that the cloud bases were only 300-800 feet above ground level; so if the stratus clouds were really close to 9000 feet thick, it was remarkable to be able to see hints of surface features through such a cloud layer!

GOES-12 sounder Cloud Top Height