Tag Archives | AVHRR

Tropical Storm Andrea clouds up the ocean

False-color image from NOAA-18 at 4:36pm on June 7, 2013

This week, was the start of the 2013 Hurricane Season, and already forecasters have declared the first storm of the season. So with one week down, I’d say we’re on track to meet NOAA’s prediction of an active to extremely active season.

Tropical Storm Andrea started as a small storm system in the in the Gulf of Mexico earlier this week, and by Wednesday evening she had grown (barely) into a low level Tropical storm. Tropical Storm Andrea then made landfall in the Big Bend region of Florida, causing some minor coastal flooding and wind damage in the Tampa area, before heading up the eastern seaboard. For the most part, Andrea was primarily a major rain event, dampening the spirits of many who are anxious for summer to finally arrive.

Large storm systems are also a nuisance to satellite oceanographers, who generally need a clear view of the ocean to measure physical variables like sea surface temperature, or the amount of chlorophyll and sediment in the water.

The image above was generated using data collected by the AVHRR instrument on NOAA-18 as it flew over the area at 4:36pm. AVHRR does not collect data in the visible light range, so this false-color representation was created by converting data from the red and infrared channels on the satellite into an image resembling a true-color photo.

What is clear from this image, is that the sky is not so clear over the ocean. In fact, the only clear areas over water are off the coast of South Carolina and over the Great Lakes, which show up as dark blue. To an oceanographer then, this image doesn’t offer much to look at, but for a meteorologist, it’s a different story.

For more on the aftermath of Tropical Storm Andrea’s deluge, I encourage you to check out the New Jersey CoCoRaHS site tomorrow to see how much rain fell on the state.

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A Colorful Winter Storm

A major winter storm made its way across the continental United States this week, dropping snow across the Dakotas, then the Midwest and the Mid-Atlantic before finally heading out to sea over the Northeast. While snowfall from the storm was difficult to forecast precisely, nonetheless it still caused major damage across many states.

The image above shows what the storm looked like at 9am EST on March 8, 2013, through the false-color eyes of the AVHRR instrument on board satellite NOAA-16. Unfortunately, AVHRR was not designed to measure visible light as many more modern satellites do. It’s primarily used for measuring the surface temperature of land and the ocean. The colors in the above image were approximated with a computer algorithm that converted AVHRR’s red, near-infrared and infrared channels into red, green and blue, creating this non-traditional colorful image of the Mid-Atlantic.

While the colors in this image can not be regarded as real, they are still useful. The white clouds are colder and generally higher in the atmosphere, while yellow clouds are slightly warmer and lower. Most of the clouds connected with the storm system are yellow. Storm bands are also visible as semi-circles pushing in towards Massachusetts and on down into New Jersey. This counterclockwise rotation is a common feature of a Nor’easter.

In advance of the storm, scientists at Rutgers deployed an underwater glider to measure how the storm will mix sediment in coastal waters. The glider certainly saw a lot of action, as wave heights reached 14 feet at the New York Harbor entrance, 24 feet off the coast of Virginia Beach, and 30 feet at the Hudson Canyon as the storm’s center passed by late on March 6th.

Special thanks to Steve Miller at NRL-Monterey for the code used to create this image.

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