This tool calculates growing degree days from daily or from spline interpolated monthly observations for a given threshold. It also calculates the julian day at which a specific target temperature sum is reached. 
|   | Name | Type | Identifier | Description | Constraints | 
| Input | Mean Monthly Temperatures | Grid list (input) | TMEAN | Monthly (12) temperature observations. | - | 
| Output | Number of Days above Base Temperature | Grid (output) | NGDD | Number of days above base temperature. | - | 
 | Growing Degree Days | Grid (output) | TSUM | Integral of daily temperature above base temperature. | - | 
 | First Growing Degree Day (*) | Grid (optional output) | FIRST | First growing degree day of the year (1-365). | - | 
 | Last Growing Degree Day (*) | Grid (optional output) | LAST | Last growing degree day of the year (1-365). | - | 
 | Degree Sum Target Day (*) | Grid (optional output) | TARGET | Day of the year at which temperature sum is reached (1-365). | - | 
| Options | Grid System | Grid system | PARAMETERS_GRID_SYSTEM | - | - | 
 | Base Temperature | Floating point | TBASE | Base temperature in degree Celsius | Default: 10.000000 | 
 | Degree Sum | Floating point | TTARGET | Target temperature sum in degree Celsius. | Default: 100.000000 | 
| (*) optional |