# Initialization¶

Defines how the inital temperatures are generated for the model.

**Example:**

```
Initialization:
Initialization Method: STEADY-STATE # KUSUDA | CONSTANT | STEADY-STATE
Accelerated Initialization Timestep: 168 # hours
Number of Accelearted Initialization Timesteps: 12
Number of Warmup Days in Initialization: 365 # days
```

## Initialization Method¶

The initialization method determines how the initial temperatures in the domain are set. Options are:

`CONSTANT`

, spatially-constant initial temperature,`KUSUDA`

, a one-dimensional analytical solution developed by that provides temperature variation as a function of depth driven by an annual harmonic temperature fluctuation. There is no temperature variation in horizontal dimensions,`STEADY-STATE`

, a steady-state solution scheme initializes the temperatures with the first timestep’s boundary conditions. This provides an initial condition temperature variation in all dimensions.

Required: |
No |

Type: |
Enumeration |

Values: |
`CONSTANT` , `KUSUDA` , or `STEADY-STATE` |

Default: |
`STEADY-STATE` |

## Initial Temperature¶

When Initialization Method is `CONSTANT`

this specifies the temperature to use.

Required: |
Depends |

Type: |
Numeric |

Units: |
K |

## Accelerated Initialization Timestep¶

An accelerated initialization begins with the user-defined Initialization Method and calculates new domain temperatuers prior to the beginning of the simulation using long timesteps (on the order of days, weeks, or months). These timesteps are calculated using a fully implicit, unconditionally stable numerical scheme. This allows the simulation to build a history of temperatures without requiring a signficant amount of additional calculations. The defualt, one week, was found to give very accurate initial temperatures.

Required: |
No |

Type: |
Integer |

Units: |
hours |

Default: |
168 |

## Number of Accelerated Initialization Timesteps¶

This specifies the number of timesteps (of the size specified by Accelerated Initialization Timestep) to calculate prior to the beginning of the simulation.

Required: |
No |

Type: |
Integer |

Default: |
12 |

## Number of Warmup Days in Initialization¶

Additional days of initialization can be calculated using the Timestep and `Numerical Scheme`_ defined by the user. This input specifies the number of days the domain is simulated under these conditions after the accelerated initialization timesteps, but prior to the Start Date specified in the Simulation Control.

Required: |
No |

Type: |
Integer |

Units: |
days |

Default: |
365 |