Model SpinUp¶
The land surface model “spinup” process is used to generate a reasonable initial state from which the model can proceed. Because the model state variables are generally not available from an independent source (amount of detained precipitation and snowmelt, for example), the model is run iteratively to generate its own initial state. The spinup is performed in three phases, representing a combination of techniques discussed in Rodell et al [20].
SpinUp Cycle #1¶
In the first spinup cycle, the model is initialized with a “garbage” initial state. It is then run into the future for an arbitrary 100 years with reasonable forcing values (monthly climate norms). While the resulting state is not an accurate representation of any point in time, it represents a “reasonable” state that is no longer affected by the choice of values in the initial state.
SpinUp Cycle #1 


Duration 
100 years 
Initial Condition 
“Garbage” initial state with detention variables
at zero, and soil moisture at 30% of capacity
( 
Forcing Data 
Monthly norm forcing calculate from period of
historical record ( 
Result files 
Discarded 
State files 
Only final state saved ( 
SpinUp Cycle #2¶
During the second phase of the spinup, the model state in January 1948 is assumed to be the final state of the 100year run performed in the first phase. The model is then run with the full history of observed forcing data (i.e., January 1948  present). The model state after each iteration is stored, and permonth average states are computed.
SpinUp Cycle #2 


Duration 
Full historical period 
Initial Condition 
Final state from cycle 1 ( 
Forcing Data 
Historical forcing data
( 
Result files 
Discarded 
State files 

SpinUp Cycle #3¶
In the final phase of the spinup, the model state in January 1948 is assumed to be the mean state of all Januaries in the second phase. The model is run with the full history of observed forcing data, and all model results and states are retained. A subset of the results from this spinup phase (e.g., 19502009) is used to fit statistical distributions of model outputs.
SpinUp Cycle #3 


Duration 
Full historical period 
Initial Condition 
Mean January state from cycle 2
(mean of 
Forcing Data 
Historical forcing data
( 
Result files 

State files 
