Table 1. WBCS climatic parameters and bioclimatic indexes.
| Climatic parameters | |
| T | average annual temperature in degrees centigrade |
| Ti | average monthly temperature, where i: 1 = January,…, 12 = December |
| M | average temperature of the maximums of the coldest month of the year |
| m | average temperature of the minimums of the coldest month of the year |
| Tmax | average temperature of the hottest month of the year, in degrees centigrade |
| Tmin | average temperature of the coldest month of the year, in degrees centigrade |
| Tp | positive annual temperature: total in tenths of degrees centigrade of the average monthly temperatures higher than 0°. ∑Ti (1–12) > 0°C, where i: 1 = January,…, 12 = December |
| Tps | positive temperature of the summer quarter, in tenths of degrees centigrade, if Ti>0 |
| P | annual precipitation in millimeters or liters per square meter |
| Pi | monthly precipitation, where i: 1 = January,…, 12 = December |
| Pcm1 | precipitation of the warmest four months of the year |
| Pcm2 | precipitation of the four months following the warmest of the year |
| Pcm3 | precipitation of the four months before the warmest of the year |
| Pp | positive annual precipitation (of the months with a Ti higher than 0°C). ∑ Pi, Ti > 0° |
| Ps | precipitation of the summer quarter |
| Pw | precipitation of the winter quarter |
| Pps | positive precipitation of the summer quarter. ∑ Ps, Ti > 0°C |
| Ppw | positive precipitation of the winter quarter. ∑ Pw, Ti > 0°C |
| Pss | precipitation for the warmest six months of the year |
| Psw | precipitation for the coldest six months of the year |
| Bioclimatic indexes | |
| Ic | Continentality/Oceanity Index: Annual thermal amplitude Ic = Tmax-Tmin, in degrees centigrade |
| Itc = Cti | Compensated Thermicity Index: It = (T + m + M) x 10 ±C |
| (To calculate C, visit https://www.globalbioclimatics.org) | |
| Io | Annual Ombrothermic Index: Io = (Pp / Tp) x 10 |
| Iosi | Ombrothermic Index of any summer month: Iosi = (Psi/Tsi)10 |
| Ios2 | Ombrothermic Index of the warmest two-month period of the summer quarter (Tr3) |
| Iosc3 (= Ios3) | Compensable Ombrothermic Index for the summer quarter (Tr3), used to assess summer aridity |
| Iosc4 (= Ios4) | Compensable Ombrothermic Index for the four-month period resulting from adding to the summer quarter (Tr3) the immediately previous month. Used to assess summer aridity |
| Iod2 | Ombrothermic index of the driest two months in the driest quarter of the year |
Adapted from: Rivas-Martínez S, Rivas Sáenz S, Penas A. Worldwide Bioclimatic Classification System. Global Geobotany 2011;1: pp 5–6.