Comparing SPI and SPEI to detect different precipitation and temperature regimes in Chile throughout the last four decades

Droughts are one of the main environmental challenges facing the world this century. The latitudinal and orographic characteristics of continental Chile leads different areas within it to experience very different regimes of precipitation and temperature, resulting in a wide variation in the occurrence and severity of droughts. Using the CR2Met 5 x 5 km resolution gridded monthly dataset covering the years from 1979 to 2019, we calculated the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evaporation Index (SPEI) of March and September at 3-, 6-, 9-, 12- and 24-months to: 1) relate them with different climate modes, and 2) determine their temporal evolution. We found that the Pacific Decadal Oscillation shows low positive correlations with SPI but no significant correlations with SPEI. The Multivariate El Nin similar to o Southern Oscillation shows different correlations in northern Chile, as well as El Nin similar to o 1 + 2 and the Antarctic Oscillation, for both SPI and SPEI. Both SPI and SPEI show negative (drier) trends in the north and center of Chile, while positive (wetter) trends appear in the south. SPEI shows stronger and more significant negative trends, influenced by the overall warming of the country. Warming trends are lower on the coast, so SPI could be a good indicator for coastal areas, while SPEI could be a good indicator for inland areas. Climate modes are useful for monthly and annual predictions, and by being a good drought predictor, they can help inform key public policies. These results are expected to help Chilean decision makers dealing with the challenges facing water management in the immediate future.

Automated summary

Droughts pose a major environmental challenge for Chile due to its geographical characteristics. Different regions in Chile experience varying levels of precipitation and temperature, resulting in different occurrences and severity of droughts. This study found that different climate modes show correlations with the Standardized Precipitation Index (SPI) and Standardized Precipitation Evaporation Index (SPEI). There are negative drought trends in the north and center of Chile, while positive trends appear in the south. The SPEI shows stronger and more significant negative trends, influenced by the overall warming of the country. Climate modes can be useful for drought prediction and informing public policies.