The long-term variability scale is important in the inter-tropical Pacific with regards to the El Niño – Southern Oscillation (ENSO) phenomenon. From a meteorological viewpoint, El Niño periods in the western Pacific, are dry, with less nebulosity, stronger winds and cooler temperatures. Such periods feature a negative Southern Oscillation Index (SOI), while the opposite climatic regime, called La Niña, has a positive SOI.