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PEI Announces 2012 Walbridge Fund Graduate Award Winners

Cloud microphysics, ecosystem stress in African savannas and nutrient-carbon feedbacks in the tropics are the topics of graduate projects awarded through the 2012 Walbridge Fund. Selected by the Princeton Environmental Institute (PEI), this year’s awardees, Minghui Diao, Kaiyu Guan and Annette Trierweiler, will receive between $6,000-7,000 grants to cover expenses such as fieldwork, travel, conference participation, equipment, data analysis, and facilities use.

Initiated in 2009, the PEI Walbridge Fund Graduate Award has provided support to Princeton graduate students pursuing innovative projects in the fields of energy technology, carbon policy, and climate science.

Minghui Diao


Minghui Diao during the Hiaper Pole-to-Pole Observations (HIPPO) in August, 2011. She is checking research equipment inside the NSF Gulfstream-V research aircraft before the research flight from Christchurch, New Zealand to the Antarctic. (Photo: Minghui Diao)

Diao, a student in the department of civil and environmental engineering, was awarded for her project “Ice Supersaturation and Cirrus Cloud Formation by Global In-Situ Aircraft Observations and Relationships with Anthropogenic Emissions.” Diao will use the Walbridge funds to travel to Thailand this summer to conduct eight weeks of fieldwork as a participant of NASA’s Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS) campaign. She will take part in daily flight planning meetings, test hypotheses on the links between air pollution, ice supersaturation, and cirrus cloud formation, and present her findings on cloud microphysics to colleagues in the field as well as at the upcoming American Geophysical Union meeting in San Francisco this fall.

“In the coming months, I plan to address the impact of anthropogenic aerosols on cirrus cloud formation and lifecycle based on the SEAC4RS campaign. Three research aircrafts will sample through cirrus clouds inside and outside biomass burning plumes over regions of Southeast Asia. Using the measurements gathered in this campaign, I will be able study aerosol-cloud interactions in a very unique way,” said Diao.

Diao hopes her research will lead to an improved quantitative understanding of the effects of anthropogenic aerosols on cirrus cloud formation as well as the clouds impacts on the global climate system.

Kaiyu Guan


Kaiyu Guan in civil and environmental engineering professor Eric F. Wood’s Land Surface Hydrology Lab. (Photo: Kaiyu Guan)

Guan was chosen for his proposal “Scaling Up Plant Water Stress of an African Savanna Ecosystem Using Unmanned Aerial Vehicle (UAV) Based Sensing.” As part of his Ph.D. research in the department of civil and environmental engineering, Guan is developing novel sensing technology to evaluate ecosystem stress in African savannas linked to climate change and land use conversion.

Guan will use the Walbridge Award to further develop an integrated UAV-based multi-spectral sensor system he built at Princeton to quantify how different savanna plant functional types, such as trees and grasses, respond to water stress at the landscape level. His planned field season in Mpala, Kenya will take place at the end of the region’s rainy season from November 2012 to January 2013 when he hopes to capture pronounced stress states of the local vegetation. Discussing his research plans, Guan said, "I hope to become a pioneer in applying the UAV-sensing technology in ecosystem research, and solving key science questions related to water stress in savanna ecosystems.”

Through his collection of landscape-scale UAV data, Guan aims to bridge an existing gap between satellite remote sensing observations and ‘single-site’ measurements in order to better understand the scaling relationships for savanna ecosystems and associated rainfall regimes.

Annette Trierweiler


Annette Trierweiler collecting nitrogen fixing nodules and forest soil chemistry samples on Barro Colorado Island, Panama. (Photo: Annette Trierweiler)

Trierweiler was selected for her project, “The Response of Tropical Nitrogen-Fixing Trees to Phosphorus and Molybdenum Limitations, Nitrogen Deposition at Pre-Industrial, Present Day, and Elevated Carbon Dioxide (CO2) Levels.” For her graduate research in the department of ecology and evolutionary biology, Trierweiler will study how specific nutrients may limit the tropical biosphere’s capacity to respond to CO2 fertilization.

With this award, Trierweiler plans to conduct greenhouse and in situ field experiments in Panama as well as develop a mechanistic model to further understand the controls of biological nitrogen fixation in tropical forest environments.

“We must first understand how phosphorus and molybdenum limitation affect nitrogen fixation at increasing CO2 levels in the tropics before we can fully understand how nitrogen availability may affect tropical forest response to climate change,” Trierweiler explained.

Trierweiler hopes her research will inform the incorporation of nutrient-carbon feedbacks in the next generation of land carbon and climate change models.