ITH index calculation is made from gridded observational or model data. If the data is needed in lat/lon projection is better to use first the load.by.variable function to change projection
The index is calculated as:
$$ITH = 1.8 * T(ºC) + 32 - (((0.55 - (0.55 * RelHum(\%))) / 100) * ((1.8 * T(ºC)) - 26))$$
where T(ªC) is the temperature in celsius degrees and RelHum(%) is the relative humidity in percentage
ith(raster.list = raster.list)
Spat Raster with ITH calculation for each time
Spat Raster variable with several variables and times or only one Spat Raster field