Archives for category: Meteorology


Few images are as beautiful and as terrifying as a satellite view of a hurricane about to make landfall. On October 29, 2012, the Suomi NPP satellite captured an ominous nighttime view of Sandy—an enormous hybrid storm that was part hurricane, part Nor‘easter—churning off the coast of New Jersey.

The string of city lights that stretches from Washington to Boston was mostly gone, blanketed by thick, ghostly storm clouds. One of the most brightly lit cities in the world, New York, was little more than a faint smudge through Sandy’s clouds.

In a matter of hours, that smudge of light would go dark. Large swaths of Manhattan were under water. The Rockaways were on fire. Rooftops along the New Jersey shore became temporary islands for people escaping a wall of seawater that surged inland.

Was Superstorm Sandy an expression of a “new normal” for our weather? Was it a storm pumped up by global warming?

“If you look at the unique set of circumstances in which Sandy emerged and you know something about meteorology and climate,” says Marshall Shepherd, director of the atmospheric sciences program at the University of Georgia, “it’s hard not to ask yourself these kinds of questions.”

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NASA Earth Observatory, March  2013

The scenes of devastation and wreckage that Hurricanes Sandy (2012) and Katrina (2005) left behind were tragically similar. Both storms flooded major cities, cut electric power to millions, and tore apart densely populated coastlines. But from a meteorological perspective, the storms were very different.

Katrina was a textbook tropical cyclone, with a compact, symmetrical wind field that whipped around a circular low-pressure center. Like most tropical cyclones, Katrina was a warm-core storm that drew its energy from the warm waters of the tropical Atlantic Ocean. Sandy had similar characteristics while it was blowing through the tropics. But as the storm moved northward, it merged with a weather system arriving from the west and started transitioning into an extratropical cyclone.

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Earth Observatory, February 2013

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Satellites provide dramatic views of clouds, but in order to understand the processes that underlie how clouds form and evolve, scientists turn to complex computer models that simulate Earth’s atmosphere. By feeding a range of ground, aircraft and satellite data into Goddard’s Earth Observing System Model (GEOS-5), research meteorologists can see how closely the mathematical equations used to simulate atmospheric dynamics match reality. Such models are by no means perfect, but they have improved tremendously in recent years. The visualizations below, based on GEOS-5 model runs from February 2010, show how well the model reproduced the massive blizzard known as “Snowmaggedon.” In the visualization, watch Snowmaggedon’s sprawling, comma-shaped cloud system—complete with a tail that reaches all the way to the Caribbean—as it churns up the Eastern Seaboard dumping three feet of snow in some areas.

NASA Visualization Explorer, January 2012 

The record-breaking drought in Texas that has fueled wildfires, decimated crops, and forced the sale of cattle herds has also reduced levels of groundwater to the lowest levels observed in more than 63 years. Groundwater is moisture trapped in pores in the soil and in underground gaps in rock, often known as aquifers.

The map above depicts the amount of groundwater stored underground in the continental United States on November 28, 2011, as compared to the long-term average from 1948 to 2011. Deep reds reveal the most depletion, with deep blues representing aquifers and soils that are nearly full. The maroon shading over eastern Texas, for example, shows that the ground has been this dry less than two percent of the time between 1948 and the present.

At the end of November 2011, groundwater supplies were extremely depleted in more than half of Texas, as well as parts of New Mexico, Louisiana, Alabama, and Georgia. The northeastern states and the High Plains appear saturated with water heading into winter months.

Earth Observatory, November 2011