Changing seasonality is perhaps the most important change in precipitation patterns observed so far. In the south in particular, there are indications that the rainy season has become more intense and more seasonally concentrated, while the dry season has become longer (Seth et al., 2010). Precipitation in the Tropical Andes also has great yearly and decadal variation. This is mainly due to the El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) climate systems. It is important to remember that ENSO events have spatially and temporally different and asynchronous effects in different parts of the Tropical Andes. Along the lower slopes of the Tropical Andes, El Niño events generally cause heavy rainfall. However, this rainfall does not reach above 2000 m.a.s.l. In fact, El Niño events generally lead to warm and dry weather in the high elevations of the Tropical Andes and along the eastern slopes. La Niña events, on the contrary, generally cause cold and wet conditions in the high mountains. In the Central Andes, this influence is less significant and less uniform (Chevallier et al., 2010).
From collection: Outlook on climate change adaptation in the Tropical Andes mountains
GRID-Arendal and Cartografare il Presente/Riccardo Pravettoni