El Niño Precipitation Anomaly

El Niño events—characterized by unusually warm ocean temperatures in the eastern equatorial Pacific—are strongly associated with changes the atmospheric circulation. In particular, rainfall patterns tend to shift—e.g., heavier rainfall patterns along the Equator. Such changes drive a variety of excessive and deficient rain anomalies in specific regions. The overall global total rainfall changes very little.

The top visualization shows rainfall amounts, while the bottom visualization shows rainfall anomalies. The actual rainfall amounts are important because those are the amounts that humans, the biosphere, and the environment experience; the anomalies reveal where the rainfall is above or below average. The data were computed from the international constellation of precipitation-relevant satellites, numbering about 10 during this time. The computational scheme was developed as part of the Tropical Rainfall Measuring Mission (TRMM), and this particular dataset, the TRMM Multi-satellite Precipitation Analysis - Real Time (TMPA-RT), is generated about 8 hours after the data are observed. The climatology, or average condition, used in the anomalies is computed from 12 years of TMPA-RT data. Since day-to-day rainfall is highly variable, 30-day running averages are shown to demonstrate the underlying patterns as time progresses.