Time Series Analysis of Soil Freeze and Thaw Processes in Indiana.
Tushar Sinha and Keith Cherkauer. Purdue University, ABE Department, 225 S University Street, West Lafayette, IN 47907
Seasonal freezing and thawing cycles influence surface energy and water cycle fluxes. Specifically soil frost can lead to a reduction in infiltration and increase in runoff response, resulting in a greater potential for soil erosion. Soil erosion potential may also increase through the weakening of soil bonds due to repeated soil freeze-thaw cycles. A study of the presence of significant trends in soil freeze-thaw cycles and soil temperatures at several depths has been performed for three research stations located in northern, central and southern Indiana that have collected soil temperature observations since 1966. Data is checked for significant autocorrelations and trends are tested at a significance level of 5% using simple linear regression, cumulative deviations, and Mann Kendall's tests. Trends have been identified and compared with other climatic variables including air temperature, snowfall, snow cover and precipitation. Results indicate that the soil freeze-thaw cycles, the number of days with soil frost and the mean maximum air temperature for winter months are increasing in northern, central and southern Indiana. Annual snowfall amounts are decreasing for northern Indiana while the annual number of snow covered days is increasing for southern Indiana. No significant trends are observed in the annual onset day of soil frost and annual or seasonal precipitation. Model simulations from a macroscale hydrologic model are compared with the observed trends in historic data to extend the spatial and temporal extent of analysis in Indiana.