By virtue of its relatively low latitude and already marginal snowpack, especially in Arizona and much of New Mexico, the southwestern U.S. is a compelling location in which to study how temperature and seasonal snowpack interact to affect spring hydroclimatology. Understanding snowpack-mediated spring soil moisture and how observed, current changes in the regional climate affect the snowpack-soil moisture relationship will provide important insights into the current and future hydrology of the southwestern U.S. In this study, we use newly available data from the North American Land Data Assimilation System (NLDAS-2) Phase 2, run with the Mosaic land surface model, to investigate the effects of recent historical trends and interannual variability (1979-2009) on land surface hydroclimatology in the Southwest U.S. There are multiple feedback mechanisms by which snowpack in the southwestern U.S. may indirectly influence short term and/or long-term climate variability. This study represents the first attempt to use newly available land surface data to describe the processes by which snowpack alters soil moisture and surface energy fluxes, thus characterizing the potential for land surface-atmosphere interactions to proceed in the southwestern U.S. We study the period between snow ablation and monsoon onset and find positive linear trends in spring temperature, decreasing linear trends in total precipitation, linear trends towards earlier snowmelt, decreasing linear trends in soil moisture and latent heat flux and increasing linear trends in sensible heat flux and the Bowen Ratio. We find that snowpack alters the magnitude and timing of soil moisture and the surface energy balance, though our sample sizes are small and the sizes of the uncertainties in the means are large. While monsoon onset negates these effects later in the year, decreased snowpack will likely exacerbate temperature-driven warming and drying, months after the complete ablation of snowpack. NLDAS-2 provides a unique opportunity to consider potential large-scale interactions of land surface hydrologic variables. With additional quantification of how the land surface behaves under changing climate conditions, we may be better able to anticipate future land surface variability and feedbacks and assess model projections with a better foundation of results from current climate change.
Earth and Planetary Sciences
Level of Degree
Department of Earth and Planetary Sciences
Gutzler, David S.
First Committee Member (Chair)
Second Committee Member
New Mexico Experimental Program to Stimulate Competitive Research (NM EPSCoR)
climate trends, interannual variability, North American Land Data Assimilation System, soil moisture, snow, hydroclimatology
Keller, Sarah J.. "Trends and interannual variability in snowpack and spring season hydroclimatology in the southwestern United States." (2011). http://digitalrepository.unm.edu/eps_etds/43