Pearson’s correlation coefficients (r – above the diagonal) and Spearman's rank correlation coefficients (ρ – below the diagonal) among some representative climatic variables, components and drought severity estimators.

<p>Bold: significant values: <0.05 for r or <−0.5 and >0.5 for ρ.</p><p>DI_T: Normalized Annual Thornthwaite Drought Index.</p><p>DI_H: Normalized Annual Hamon Drought Index.</p><p>DI _{max N}: Normalized Maximum Month Drought Index (Thornthwaite (T) or Hamon (H)).</p><p>F#i: Two main components using all bioclimatic variables (i = T), only precipitation variables (i = P), or only drought-related variables (i = S) (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062898#pone-0062898-t001" target="_blank">table 1</a>).</p><p>Original Control Bioclimatic Variables: P12: Annual Precipitation, P14: Precipitation of Driest Period, P1: Annual Mean Temperature, P9: Mean Temperature of Driest Quarter.