Archive for September, 2016

Julia: A Drenching, Perplexing Tropical Storm

September 28th, 2016 by Kathryn Hansen

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Tropical Storm Julia made headlines in September 2016, but not in the usual way. It wasn’t a particularly strong or destructive storm, although it brought heavy rainfall to coastal areas of the eastern United States from Florida to Virginia. The unusual aspect was where it formed: Julia became a tropical storm while over land, not over the ocean.

The image above, acquired at 11:55 a.m. Eastern Daylight Time (15:55 Universal Time) on September 14, 2016, with the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, shows Julia over the southeastern United States. At the time, the storm was moving toward the east and had maximum sustained winds of about 55 kilometers (35 miles) per hour.

A NASA-funded study in 2013 by meteorologists Theresa Andersen and Marshall Shepherd described a new category of storm—one that draws energy from water on land. The research showed that some storms can derive energy from the evaporation of abundant soil moisture. Since publishing the research, Shepherd and colleagues have received frequent inquiries as to whether a particular storm was influenced by this “brown ocean” effect. In the case of Julia, the answer is not clear.

“I personally find it overly speculative to make that linkage right now,” Shepherd said. “Frankly, the Baton Rouge floods may have more of a link to the brown ocean than this event, which experienced quite a bit of moisture advection from the ocean.”

The uncertainty in Julia’s case comes from its position. Although the storm developed its center while over land, it was still too close to the ocean for scientists to distinguish an influence from land-based water. Read Shepherd’s full explanation here.

September Puzzler

September 20th, 2016 by Adam Voiland

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Every month on Earth Matters, we offer a puzzling satellite image. The September 2016 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.

How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money or a trip to Mars, but, we can promise you credit and glory. Well, maybe just credit. Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. In the credits (and also on this blog), we will acknowledge the person who was first to correctly ID the image. We may also recognize certain readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you want us to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the last few months or work in geospatial imaging, please sit on your hands for at least a day to give others a chance to play.

Releasing Comments. Savvy readers have solved some of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.

Good luck!

Editor’s Note: Congratulations to Cait Stuart, Tyler Keaton, and Rosemary Butt for being some of the first readers to solve the puzzler on Facebook. Congratulations to Adam Liefloff for being the first to weigh in with the answer on Earth Matters. See a labeled version of the September puzzler here.

 

 

While I was interviewing University of North Carolina climate scientist Wei Mei about his new research that shows a significant increase in the intensity of land-falling typhoons in the western Pacific, the strongest storm of the 2016 season (Super Typhoon Meranti) was on the verge of slamming into China after grazing Taiwan.

“Meranti fits the trend,” said Wei. “In 2016 so far, there have been six typhoons in the northwestern Pacific. Three have already made it to category 4 or 5. In the late 1970s, only about one-quarter of typhoons reached that strength. Now about half do.”

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NASA Earth Observatory MODIS image of Super Typhoon Meranti.

Some meteorologists have mused that with sustained winds of 165 knots (190 miles per hour), Meranti would have been the equivalent of a Category 6 storm—if the Saffir-Simpson scale actually went that high. (It maxes out at 5). Even though Meranti only grazed southern Taiwan, it still knocked out power to 500,000 households and produced giant waves along the coast.

The focus of Mei’s research, however, is not Meranti or the 2016 typhoon season. Working with colleague Shang-Ping Xie of Scripps Institution of Oceanography, Mei has been digging through records that detail every typhoon in the northwestern Pacific since 1977 and looking for changes in the intensity of storms. What they found was a strong increase in typhoon intensity. Overall, landfalling storms strengthened by about 15 percent over the past four decades, with the proportion of typhoons reaching categories 4 and 5 more than doubling. Mei and Xie showed that storms that passed over waters relatively near to land and moved toward land (red and green dots in the chart below) have strengthened the most. Those that stayed out over the open ocean (black and blue dots) did not strengthen by a significant amount.

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Figure from Mei and Xie, 2016.

“Elevated rates of warming in coastal seas (in comparison to the open ocean) are the reason for the intensification of land-falling typhoons,” said Mei. Between 1977 and 2013, many coastal areas in Asia have warmed by upwards of 0.20 degrees Celsius (0.36 degrees Fahrenheit) per decade along the coasts—more than twice as much as open ocean areas.  In the chart below, notice all the deep reds (more warming) near the coasts; farther out to sea tends to be yellow and orange (less warming).

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Figure from Mei and Xie, 2016.

“We are not arguing that the warming of the coastal seas is due to greenhouse gas-driven climate change; that would require attribution studies that we have not conducted yet,” he said. “But we feel confident that land-falling storms are getting stronger because of rising sea surface temperatures, particularly in a band off the coast of East and Southeast Asia.” A related 2015 study led by Mei argued that sea surface temperatures are a more important factor in controlling long-term variations in typhoon intensity than other factors, such as vertical wind shear.

In this study, Mei and Xie did not look at the frequency of storm development. Some storm researchers have argued that a warming world may make hurricanes and typhoons stronger but less frequent.

For more details about Mei and Xie’s latest study, read more from Scripps Institution of Oceanography, The Verge, and Nature Geoscience.

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Himawari-8 image of Super Typhoon Meranti and night lights (in orange) of Asia via Colorado State University and Mashable.

 

Visualizing the Warmest August in 136 Years

September 12th, 2016 by Leslie McCarthy & Michael Cabbage

August 2016 was the warmest August in 136 years of modern record-keeping, according to a monthly analysis of global temperatures by scientists at NASA’s Goddard Institute for Space Studies (GISS).

Although the seasonal temperature cycle typically peaks in July, August 2016 wound up tied with July 2016 for the warmest month ever recorded. August 2016’s temperature was 0.16 degrees Celsius warmer than the previous warmest August (2014). The month also was 0.98 degrees Celsius warmer than the mean August temperature from 1951-1980.

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NASA Earth Observatory chart by Joshua Stevens, based on data from the NASA Goddard Institute for Space Studies.

 

“Monthly rankings, which vary by only a few hundredths of a degree, are inherently fragile,” said GISS Director Gavin Schmidt. “We stress that the long-term trends are the most important for understanding the ongoing changes that are affecting our planet.” Those long-term trends are apparent in the plot of temperature anomalies above.

The record warm August continued a streak of 11 consecutive months (dating to October 2015) that have set new monthly temperature records. The analysis by the GISS team is assembled from publicly available data acquired by about 6,300 meteorological stations around the world, ship- and buoy-based instruments measuring sea surface temperature, and Antarctic research stations. The modern global temperature record begins around 1880 because previous observations didn’t cover enough of the planet.

Related Links
+ For more information on NASA GISS’s monthly temperature analysis, visit: data.giss.nasa.gov/gistemp.

+ For more information about how the GISS analysis compares to other global analysis of global temperatures, visit:
http://earthobservatory.nasa.gov/blogs/earthmatters/2015/01/21/why-so-many-global-temperature-records/

+ To learn more about climate change and global warming, visit:
http://earthobservatory.nasa.gov/Features/GlobalWarming/

Related Reading in the News
+ Mashable: Earth sets record for hottest August, extending warm streak another month
http://mashable.com/2016/09/12/earth-warmest-august-hottest-summer/#ivXnyy8yusqu

+ XKCD: A Timeline of Earth’s Average Temperature
http://xkcd.com/1732/

+ Climate Central: August Ties July as Hottest Month Ever on Record
http://www.climatecentral.org/news/august-ties-july-as-hottest-month-on-record-20691