“…Pearson correlation analysis (PCA) was used to figure out whether the SMOS-SM is robust enough for detecting drought. By using PCA, the correlation coefficient could be obtained, which reflects the degree of correlation of two variables [51]. In this study, the PCA is carried out between SMOS-SM and every in situ meteorological index, i.e., 1-, 3-, 6-, 9-and 12-month SPI (SPI-1, SPI-3, SPI-6, SPI-9 and SPI-12); 1-, 3-6-, 9-and 12-month SPEI (SPEI-1, SPEI-3, SPEI-6, SPEI-9 and SPEI-12); and sc-PDSI [22,52].…”