Galapagos Islands
The Galapagos Archipelago is a volcanic island group in the eastern equatorial Pacific, roughly a thousand kilometers west of mainland Ecuador. The islands straddle the equator across a compact longitude band in the eastern Pacific.
Climate zones
Despite their equatorial location, the Galapagos Islands exhibit a remarkably diverse set of climate zones driven by the interaction of the Pacific Equatorial Undercurrent (EUC) with the island topography and the large-scale ENSO cycle.
The islands experience two main seasons:
- Hot season (January-May): Warmer sea surface temperatures, increased convective Precipitation, and a northward displacement of the ITCZ bring episodic heavy rainfall to the lowlands.
- Garua season (June-November): Cooler SSTs caused by intensified upwelling produce a persistent low-level temperature inversion. Below the inversion, Stratocumulus clouds form and produce the characteristic fine drizzle known as Garua. The highlands above approximately 300 m receive significant moisture through occult precipitation (fog interception), while the lowlands remain arid.
Vertical climate gradients
Each major island shows a pronounced vertical gradient from arid coastal lowlands through transitional zones to humid highlands. This gradient is shaped by:
- The elevation-dependent interaction with the marine inversion layer
- Orographic lifting of moist air masses
- Fog interception by vegetation at mid to high elevations
The DARWIN project studied this vertical transition through a distributed weather station network spanning coastal, transitional, and highland environments.
Oceanic influences
The climate of the Galapagos is governed primarily by oceanic processes:
- The Pacific Equatorial Undercurrent delivers cold, nutrient-rich water that upwells around the western islands, creating the Galapagos Cold Pool
- El Nino events dramatically warm SSTs around the archipelago, increasing convective rainfall and disrupting the Garua season
- The Humboldt Current brings cool water from the southeast, reinforcing the cool-dry conditions in the lowlands
Research context
The Galapagos represent a natural laboratory for studying coupled ocean-atmosphere interactions at the meso-scale. The DARWIN project used Dynamical downscaling of ERA5 reanalysis data with WRF to produce the Galapagos refined analysis.
See also: El Nino and the Galapagos, Cloud frequency in the Galapagos, MOC Galapagos Ocean-Atmosphere Coupling