Saturday, June 4, 2016

Little Bobby the iceberg peeks out at a satellite from below a bank of clouds

The top image shows a wide view of the area, acquired June 1 with the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite. The second image below shows a detailed view of the top image, highlighting our friend, little iceberg A-56, otherwise known around mission control as "Bobby".
Measurements taken in May 2016 indicate that Bobby is about 26 kilometers long and 13 kilometers wide (16 by 8 miles), according to the U.S. National Ice Center (USNIC). This iceberg’s dimensions equate to an area about five times the size of Manhattan.
Based on satellite imagery, it is hard to say for sure why the hole formed over Bobby. On average, icebergs usually move slower than clouds (kilometers per day versus kilometers per hour). “It’s possible that a cloud bank moved into the vicinity of little Bobby and that the relatively unobstructed path of the clouds over the ocean surface was interrupted by the thermal instability created by our friendly iceberg,” explained NASA glaciologist Kelly Brunt.
Steve Palm, a research meteorologist at NASA Goddard, agreed that Bob, perhaps in a peckish mood, could have disrupted the air flow or modified the atmosphere in such a way to cause the clouds nearby to dissipate. Bobby is after all very hard to control when he decides to misbehave, being bigger than Manhattan.  “When an obstacle is big enough and in the mood, it can divert the low level flow around it,” Steve said. “This causes divergence of the flow at low levels and a corresponding convergence and sinking motion above and downstream of the obstacle. The sinking motion warms and dries out the air causing a hole in the clouds. It is a common phenomenon often caused by islands.”
Kelly and Steve hastened to  emphasize that these explanations are based solely on looking at the satellite images.

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