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Nate Brunsell Assistant Professor Office: 417a Lindley Hall Phone: 785-864-2021 Email: brunsell@ku.edu Office Hours: MW 9:00-10:00 or by appointment
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A major focus of my current research has been on the interactions between spatial heterogeneity of vegetation and soil moisture on surface-precipitation feedbacks. Here, the focus is on the boundary layer dynamics associated with convective rainfall. This research began when I developed a simple methodology for separating the impacts of soil moisture and vegetation using a 20 year record of AVHRR satellite data combined with gridded precipitation across the globe (Brunsell, 2006). This methodology relies on using quadrant analysis and the lagged correlations between remotely sensed vegetation and precipitation and the correlation between radiometric temperature and precipitation. Recently a graduate student and I examined the soil moisture dynamics in more detail by using regional climate simulations in the central U. S. to assess the physical mechanisms associated with the correlation analysis (Jones and Brunsell, 2009a,b). I am currently working on another suite of simulations to assess the joint impacts of vegetation on mitigating the impacts of the soil moisture-precipitation feedback mechanisms.
Following my interests in surface-precipitation interactions, I developed a methodology for assessing the vegetation response to precipitation forcing events using a combination of wavelet multi-resolution analysis and information theory metrics. This method allows quantifying the ‘information transfer’ across the land-atmosphere interface as a function of spatial and temporal scale. This method was applied to a MODIS-NEXRAD data set to assess vegetation responses to precipitation forcing in the Missouri Basin (Brunsell and Young, 2008). This method has also been applied to examining the role of satellite spatial resolution on derived evapotranspiration using a soil-vegetation-atmosphere transfer (SVAT) modeling scheme (Brunsell et al., 2008). This wavelet-information theory approach has recently been used to address the temporal dynamics of daily precipitation variability across the continental United States (Brunsell, 2010 in press with Journal of Hydrology).
While attempting to ascertain the responses of vegetation phenology to changes in the microclimatic conditions, I have begun to examine the impacts of regional climate change in the central U. S. grasslands. This work has been motivated by an interest in understanding land cover variability in response to global climate change. Therefore, I examined the predictions of the global climate models used in the most recent IPCC report in terms of air temperature and precipitation amounts (Brunsell et al., 2010 in press with International Journal of Climatology). First, I evaluated the 1950-2000 time period using data from meteorological stations used in the Global Historical Climate Network (GHCN). This was extended to examining the trends for the twenty-first century.
Currently, I have a graduate student examining the ecological significance of these forecasts by downscaling GCM output to run the ecological process model BIOME-BGC. The GHCN data has also been used to examine the changes in drought frequency in the region. Another student will be using the 20 year AVHRR record to examine to what extent changes in vegeta- tion phenology are already occurring in the region. This satellite record will also allow me to examine the role that land use (e.g. irrigation, urbanization and woody-encroachment) plays in the cycling of carbon and water.
As a specific example of another line of current research, I am using data I collected during the CLASIC field campaign in Oklahoma to investigate the impacts of surface patch size on boundary layer development and land-atmosphere interactions (Brunsell et al. 2010, in review with Boundary Layer Meteorology). Through a combination of large eddy simulation runs with varying surface patch sizes, surface measurements and remote sensing data, I was able to separate the roles of land use and patch size on determining the microclimatic environmental conditions. In addition, this study area provides a testbed for deriving scaling relationships from the eddy covariance tower to the scale of a large aperture scintillometer to the pixel of LandSAT and MODIS. This information is vital for the routine monitoring of the land- atmosphere interface.
In addition to the modeling and remote sensing studies, I actively maintain 3 eddy covariance stations and a large aperture scintillometer within tall grass prairie ecosystems. A current graduate student is using this data to examine the impacts of variation in mean rainfall on sites experiencing woody-encroachment as well the role of fire on maintaining the carbon and water cycling dynamics. The data has already been used to examine the role of land cover variability on local carbon and water cycling (Brunsell et al. 2010, review with Theoretical and Applied Climatology) and will be used in the future for addressing the local to regional scale impacts of global climate change.
