Tropical tempests take encouragement from environment

Jul 29, 2014
In 2008, when Cyclone Nargis made landfall in Myanmar (formerly Burma), it caused large devastation. The second deadliest of all time, this Bay of Bengal cyclone was whipped up by environmental conditions favorable to tropical cyclones. Scientists are working to identify the environmental trends that favor such cyclones. Credit: NASA Earth Observatory

Mix some warm ocean water with atmospheric instability and you might have a recipe for a cyclone. Scientists at Pacific Northwest National Laboratory and the Atlanta Oceanographic and Meteorological Laboratory found that the intensity of post-monsoon tropical cyclones in the Bay of Bengal has increased over the 30-year period from 1981-2010. The culprit? Trending increases in certain environmental conditions that brew up these storms: increased sea surface and upper ocean temperatures and atmospheric instability. These particular changes are prominent in the eastern Bay of Bengal where the strongest tropical cyclones have traditionally formed.

The research shows a consistent progression in these conditions, suggesting that the Bay of Bengal will be the location of increasingly intense post-monsoon cyclones.

The Bay of Bengal, located in the Northern Indian Ocean, is marginally conducive to tropical cyclone formation. Tropical cyclones in the Bay of Bengal, however, have devastating consequences when they hit land due to a combination of factors such as a low-lying and flat coastal terrain, a shallow floor, and a high population density of surrounding countries. For example, Tropical Cyclone Nargis in 2008 was responsible for the death of nearly 138,000 people in Burma (now Myanmar), and also affected Bangladesh, India and Sri Lanka. The environmental and societal toll makes it important to understand the future of in this region.

While a few studies in the past investigated the influence of climate phenomena such as the El Niño Southern Oscillation and the Madden-Julian Oscillation on the inter-annual variability of in the post-monsoon Bay of Bengal, changes in long-term cyclone activity are less well understood.

To attack this information gap, the research team analyzed 30 years of tropical cyclone track data obtained from the U.S. Navy's Joint Typhoon Warning Center. Also, they used observation data from Britain's weather and climate data organization, the UK Met Office's Hadley Center and the National Oceanographic and Atmospheric Administration (NOAA), ocean reanalysis data from the Geophysical Fluid Dynamics Laboratory at NOAA, and atmospheric reanalysis data from the European Centre for Medium-Range Weather Forecasting and NOAA's National Centers for Environmental Prediction for that 30-year period.

They found increases in temperature and upper ocean heat content made the ocean more conducive to tropical cyclone intensification, while enhanced convective instability made the atmosphere more favorable for the growth of these storms.

Scientists are working to understand the large-scale climatic conditions responsible for the observed changes in the various environmental parameters controlling tropical cyclone development.

Explore further: Correction: Hurricane vs Typhoon story (Update)

More information: Balaguru K, S Taraphdar, LR Leung, and GR Foltz. 2014. "Increase in the Intensity of Postmonsoon Bay of Bengal Tropical Cyclones." Geophysical Research Letters 41(10):3594-3601. DOI: 10.1002/2014GL060197.

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Volcano expert comments on Japan eruption

26 minutes ago

Loÿc Vanderkluysen, PhD, who recently joined Drexel as an assistant professor in Department of Biodiversity, Earth and Environmental Science in the College of Arts and Sciences, returned Friday from fieldwork ...

NASA's HS3 looks Hurricane Edouard in the eye

13 hours ago

NASA and NOAA scientists participating in NASA's Hurricane and Severe Storms Sentinel (HS3) mission used their expert skills, combined with a bit of serendipity on Sept. 17, 2014, to guide the remotely piloted ...

Tropical Storm Rachel dwarfed by developing system 90E

17 hours ago

Tropical Storm Rachel is spinning down west of Mexico's Baja California, and another tropical low pressure area developing off the coast of southwestern Mexico dwarfs the tropical storm. NOAA's GOES-West ...

NASA ocean data shows 'climate dance' of plankton

21 hours ago

The greens and blues of the ocean color from NASA satellite data have provided new insights into how climate and ecosystem processes affect the growth cycles of phytoplankton—microscopic aquatic plants ...

User comments : 0