/*!
* \brief Use this method to choose model for ET0 calculation automatically depending on available data.
*
* \param climate Parameter to relay to matching ET0 calculation model.
* \param date Parameter to relay to matching ET0 calculation model.
* \param location Parameter to relay to matching ET0 calculation model.
* \param et0PmArgs Relayed to Et0CalcPm()
* \param et0HgArgs Relayed to Et0CalcHg()
*
* \return An Et0Result structure.
*/
public static bool Et0Calc(
Climate climate,
DateTime date,
Location location,
Et0PmArgs et0PmArgs,
Et0HgArgs et0HgArgs,
ref Et0Result result
)
{
var climateSet = climate.getValues(date);
//check availability of values
if (climateSet == null)
{
return(false);
}
if (
climateSet.max_temp.HasValue &&
climateSet.min_temp.HasValue &&
climateSet.humidity.HasValue &&
(climateSet.Rs.HasValue || climateSet.sunshine_duration.HasValue)
)
{
//data sufficient for Penman-Monteith
return(Et0CalcPm(climate, date, location, et0PmArgs, ref result));
}
//use Hargreaves
return(Et0CalcHg(climate, date, location, et0HgArgs, ref result));
}
/*!
* \brief Calculate ET0 with Hargreaves method as described in FAO paper 56.
*
* \param climate Use this dataset with climate data.
* \param date Date for ET0 calculation.
* \param location The location for calculation, latitude and altitude are used.
* \param et0Args Regression coefficients for Hargreaves calculation
* \param [in,out] result Result of calculation
*
* \return true on success
*/
public static bool Et0CalcHg(
Climate climate,
DateTime date,
Location location,
Et0HgArgs et0Args,
ref Et0Result result
)
{
var climateSet = climate.getValues(date);
if (climateSet == null)
{
return(false);
}
if (
!climateSet.max_temp.HasValue ||
!climateSet.min_temp.HasValue
)
{
return(false);
}
var raResult = Ra.RaCalc(date, location);
result.ra = raResult.ra;
if (result.ra == 0)
{
result.et0 = 0;
return(true);
}
var lambda = 2.5 - 0.002361 * ((double)climateSet.max_temp + (double)climateSet.min_temp) / 2;
result.et0 = et0Args._ch * result.ra * Math.Pow(((double)climateSet.max_temp - (double)climateSet.min_temp), et0Args._eh) * (((double)climateSet.max_temp + (double)climateSet.min_temp) / 2 + et0Args._ct) / (double)lambda;
return(true);
}
