WEST LAFAYETTE, Ind. - Researchers from Purdue University and the Indian Institute of Technology Bombay have determined that rapidly urbanizing areas on the Indian subcontinent are more likely than established cities to experience extreme rainfall events during the summer monsoon season, a finding that is important for shaping storm water system design, water resource policy and urban flood management in the region.

The study could have a particularly significant impact in India, where there is a strong push underway for the development of “smart cities” and modern infrastructure.

Study co-author Dev Niyogi, Purdue professor of agronomy and Indiana state climatologist, said results of past studies of rainfall patterns might no longer be sufficient to predict future precipitation events.

“Rainfall patterns are changing throughout India,” Niyogi said. “We found that there is a need to look at both global and local conditions, such as urbanization, and how those influence climatic patterns such as rainfall.”

Using a data-driven method, the authors found a link between the extent of urbanization and changing extreme rainfall patterns.

“The possible reasons for this rainfall variability might be that since development activities in urbanized areas have already been stabilized, changes in landscape characteristics are minimal and thus local circulation patterns are not significantly altered,” Niyogi said. “However, in areas undergoing rapid development, changes in extreme rainfall patterns are significant.”

Deforestation and land transformation could be two of the main causes of increased climate stress in urbanizing areas, he said.

The study used daily rainfall data from 1901 to 2004 taken during the Indian summer monsoons season, which runs from June to September. The rainfall totals were collected by the India Meteorological Department from a network of 1,800 stations located throughout the country.

The authors found the frequency of extreme rainfall events in rapidly developing regions, including Nashik, Kanpur, Durgapur and Mangalore, exceeded those in established cities such as Mumbai, New Delhi, Kolkata and Chennai.

Niyogi’s co-authors were Subhankar Karmakar, Subimal Ghosh, Jitendra Singh and H. Vittal, all of the Indian Institute of Technology Bombay.

The study, “Urbanization causes nonstationarity in Indian Summer Monsoon Rainfall extremes,” was published in the journal Geophysical Research Letters. It is available at http://onlinelibrary.wiley.com/doi/10.1002/2016GL071238/full.

Funding for the study was provided by the U.S. National Science Foundation, and India’s Ministry of Earth Sciences.

Writer: Darrin Pack, 765-494-8415, dpack@purdue.edu

Source: Dev Niyogi, 765-494-6574, climate@purdue.edu

Agricultural Communications: (765) 494-8415;

Darrin Pack, dpack@purdue.edu

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