Auburn professor to be part of NASA-funded team tasked with studying effects of urban pollution in precipitation

Auburn University Associate Professor of Geosciences Chandana Mitra will be part of a NASA-funded national team tasked with studying whether cities can, via urban landscapes and/or associated aerosol processes, initiate or modify precipitating cloud systems.

Mitra will use a $185,400 segment of NASA’s $1.7 million grant to contribute research to the team, which includes representatives from the University of Georgia, Louisiana State University, Purdue University, Florida State University and University of Texas San Antonio, along with NASA Goddard, Universities Space Research Association Columbia and SpringGem Weather Information LLC. The project is titled “Toward Conceptualization and Predictability: A Multi-scalar Analysis of Urban-Influenced Hydrometeorological Processes.”

One of the main goals of the collaboration is to leverage NASA resources to expand analyses to under-studied regions of the globe or multiple spatial scale regarding “urban rainfall effects.” One major task of Mitra’s research will include delineating urban agglomerations in North America, South America, Africa, Asia, Europe and Australia and creating a global inventory of “urban rainfall effect” signatures on the major continents.

“I am very excited to be a part of this team and cannot wait to begin work on this NASA-funded project,” said Mitra, a physical geographer and climatologist focused on researching the impacts of urban growth on local climate, especially in the area of heat and precipitation variability. “It is critical to understand the processes by which urbanization effects precipitation and to move toward predictability of urban rain and snow events to minimize vulnerability to flooding and other associated hazards. The proposal team’s expertise in meteorology and climatology, geography, remote sensing, machine learning, land use planning and entrepreneurship makes it well-suited for tackling the most pressing remaining knowledge gaps in urban hydrometeorology using innovative methods and tools.

“This interdisciplinary team and the industry partnerships assembled here will ensure that the knowledge and datasets gained from the proposed work can be readily transitioned for use and will positively contribute to NASA’s core Earth Science Division goals.”

The grant will allow Mitra to fund a doctoral student for three years to help her study how cities across various continents initiate or modify precipitating cloud systems via urban rainfall effect. They also will use computational techniques to examine how the cloud systems are influenced by urban heat island intensity, reduced evapotranspiration and the various urban morphologies.

“It is still unclear what role urban aerosols play on precipitation formation and intensification,” she said. “Aerosols have both a negative and positive impact on urban rainfall. They have been shown to enhance rainfall by serving as cloud condensation nuclei, yet studies also have shown that aerosol loading may broaden the spectrum of small cloud droplets, which reduces precipitation efficiency, especially in warm clouds. This research will be a novel research study of direct and semi-direct aerosol effects on the physical processes of urban rainfall.”

Mitra will use remote sensing and geographic information system techniques to measure the urban heat island intensity, evapotranspiration and precipitation variability. In addition, she will co-conduct a four-dimensional analysis of rainfall, NASA Cloud Products and NASA Land Products to identify geographical tendencies in hydroclimate variability that may be driven or modulated by a combination of urban land cover, the urban heat island and aerosols.

Mitra’s Auburn team will be tasked with delivering three specific goals for the multiyear project—producing a global inventory of “urban rainfall effect” signatures on the major continents in the first year, a climatology of “non-urban” noise that might modulate or describe such signatures in year two and a GIS-based database of what urbanized geographic regions are more likely to exhibit an urban signature in spatiotemporal precipitation variability in the third year.