Canadian In Situ Snow Cover Trends for 1955–2017 Including an Assessment of the Impact of Automation

Snow cover trends for Canada over the 1955–2017 period daily snow depth–observing network of Environment and Climate Change (ECCC) are presented based on an updated quality-controlled historical in situ depth dataset. The since approximately 1995 is characterized by a rapid decline manual observations (loss 800 observing sites between 2017) increasing number automated stations equipped with sonic sensors. In 2017 these accounted 45% more than 80% north latitude 55°N. Automated frequent missing anomalous data ruler observations, particularly at Arctic sites. A comparison closely located showed similar numbers days but sensors detected significantly lower depths. For time series analysis annual variables, systematic difference can be removed using common 2003–2016 reference to compute anomalies. trend results broadly previously published assessments showing long-term decreases duration (SCD) most Canada, largest observed spring seasonal maximum (SDmax). Significant declines SCD SDmax ?1.7 (±1.1) decade-1 ?1.8 cm (±0.8) decade?1 were Canada–averaged period. These mainly reflect conditions southern where concentrated there significant negative correlations winter air temperature. Declining reporting depth, issues sensor quality, differences measurements major challenges continued climate monitoring current ECCC network.