Regional-scale land--climate interactions and their impacts on air quality in a changing climate

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Title: Regional-scale land--climate interactions and their impacts on air quality in a changing climate
Author: Jiang, Xiaoyan, doctor of geological sciences
Abstract: Land surface areas , which represent approximately 30 % of the Earth’s surface , contribute largely to the complexity of the climate system by exchanging water , energy , momentum , and chemical materials with the overlying atmosphere . Because of the highly heterogeneous nature of the land surface and its rapid transformation due to human activities , future climate projections are less certain on regional scales than for the globe as a whole . The work presented in this dissertation is focused on a better understanding of regional -scale land–atmosphere interactions and their impacts on climate and air quality . Specifically , I concentrate my research on three typical regions in the United States (U .S . ) : 1 ) the Central U .S . (representing transition zones between arid and wet climates ) ; 2 ) the Houston metropolitan region (representing a major urban area ) ; and 3 ) the eastern U .S . (representing temperate forested regions ) . These regions are also chosen owing to the consideration of data availability . The first study concerns the roles of vegetation phenology and groundwater dynamics in regulating evapotranspiration and precipitation over the transition zones in summer months . It is found that the warm -season precipitation in the Central U .S . is sensitive to latent heat fluxes controlled by vegetation dynamics . Groundwater enhances the persistence of soil moisture memory from rainy periods to dry periods by transferring water to upper soil layers through capillary forces . Enhancement in soil moisture facilitates vegetation persistence in dry periods , producing more evaporation to the atmosphere and resulting in enhanced precipitation , which then increases soil moisture . The second study compares the impacts of future urbanization and climate change on regional air quality . The results show that the effect of land use change on surface ozone (O3 ) is comparable to that of climate change , but the details differ across the domain . The third study deals with the formation and distributions of secondary organic aerosols (SOA ) — a largely overlooked but potentially important component in the climate system . Under future different climate scenarios , I found that biogenic emissions — an important precursor of SOA — are expected to increase everywhere over the U .S . , with the largest increase found in the southeastern U .S . and the northwestern U .S . , while changes in SOA do not necessarily follow those in biogenic emissions . Other factors such as partitioning coefficients , atmospheric oxidative capability , primary organic carbon , and anthropogenic emissions also play a role in SOA formation . Direct and indirect impacts from climate change complicate the future SOA formation .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2346
Date: 2011-02-09

Citation

Regional-scale land--climate interactions and their impacts on air quality in a changing climate. Doctoral dissertation, University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2346 .

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