Took a bit of searching but I've found them!
3.1.2 Climatic classification
: continentality index (yearly thermal interval), expresses the range between the average temperature of the warmest (Tmax) and the coldest (Tmin) months of the year. Ic =Tmax - Tmin.
: thermicity index, calculated as ten times the sum of the yearly average temperature (T), the average minimum temperature of the coldest month in the year (m) and the average maximum temperature of the coldest month in the year (M). It = (T+ m+ M)x10.
: compensated thermiticity index, calculated as It plus or minus a compensation value (C): Itc=It±C. This index can be considered to equal It if Ic lies between 9 and 18.
: ombrothermic index, calculated as ten times the quotient resulting value between the yearly positive precipitation (Pp) and the yearly positive temperature (Tp). Io = 10x Pp /Tp.
: in the Bioclimatic belt the termotype must be calculated through Tp value when Ic is more or equal to 21 and Itc is less than 120.'
North American boreal and western temperate forest vegetation [02_1]
Yearly Positive Temperature. In tenths of degrees Celsius, sum of the monthly average temperature of those months whose average temperature is higher than 0ºC.