Spatial and Temporal Snow Dynamics at the Southern Margin of North American Continental Snow Distribution

Snow is crucial for stream flow and water use needs of large populations throughout the western United States, especially in the arid southwest. Accurate estimates of spatial distribution and temporal dynamics of snow cover are important for forecasting as well as understanding sensitivity to future climate change. We examined regional-scale temporal trends in snow distribution across central and northern Arizona using MODIS MOD10 snow products, consisting of two tiles of 2,928 daily images between October 1, 2003 and June 1, 2014. The area studies covered a 245,041 km² area of 51 HUC8 watersheds. We employed a Mann-Kendall test to examine the temporal trends during this time period, and compared these trends at SNOTEL point locations for temporal context. We found the MOD10 snow product performs well in estimating Arizona’s thin and discontinuous snow distribution. Mann-Kendall time-series analysis indicate significantly increasing trends in the annual number of snow covered days (SCD) over the 12-year period at elevation transitions such as the Mogollon Rim in central Arizona, while significantly decreasing trends are observed at a few locations of lower elevations leading to the desert margins in eastern Arizona. These results are important in understanding the role forest restoration might play in snow accumulation and retention.