1-D EKF, only SWE of each layer is updated using the synthetic observation: SWE of the snowpack.  The state transition matrix is an identity matrix.  Snow depth and heat contents are updated solely through the model physics and the updated SWE.  The “true” states are generated from a model run, using initial condition from model spin-up forced with bias-corrected ECMWF data.  The assimilation starts on 1/1/87 with a poor initial condition of no snow anywhere. The SWE is updated using observations extracted from the true states every six hours.  For comparison, a “forecast” run is performed starting with the poor initial condition without assimilation.