Publication Date

Spring 2017

Advisor(s) - Committee Chair

Jason Polk (Director), Joshua Durkee, Xingang Fan

Degree Program

Department of Geography and Geology

Degree Type

Master of Science

Abstract

Mesoscale convective complexes (MCCs) over subtropical South America contribute an average annual volume of precipitation equal to approximately seven km3 and occur with an average regularity in the region, with more than 30 per warm season. Isotopic characteristics of precipitation, such as δ2H and δ18O values, provide information that can be used to identify unique processes and sources related to precipitation events. The largest database of isotope characteristics of precipitation within the region is the Global Network of Isotopes in Precipitation (GNIP), which provides varying temporal resolution data from stations around the world, including subtropical South America.

Using this database, isotope characteristics of precipitation samples within the study area of Brazil were examined to identify patterns in storm characteristics, the isotope characteristics in MCC events, and to assess the use of event (daily) resolution data for storm events that lasted 14 hours, on average. This research resulted in Local Meteoric Water Lines (LMWL) that describe the isotopic composition of precipitation and rivers at various points throughout the year and found precipitation within the study region much closer to the Global Meteoric Water Line (GMWL) than river water. While event (daily) resolution is useful, a greater number of samples at higher-resolution would provide better descriptions for specific storm events, such as MCCs, as well as to differentiate between MCC and non-MCC events more effectively. Differences in source waters and processes were evident in the data, meaning future research at higher resolutions could benefit from identifying the contribution of each source and process to any distinct MCC event in the region.

Disciplines

Climate | Hydrology | Other Oceanography and Atmospheric Sciences and Meteorology

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