Volcanic eruption, global monsoon, and El Niño

Seminar by Seung-Ki Min from Pohang University of Science and Technology

22 July 2020
16:00 — 17:00

The Seminar is being held in Room 1010 (Jasmin) – Intergrated mechanical engineering building. Click here for the campus map.

Tropical volcanic eruptions are known to induce a decrease in global monsoon precipitation but there remains a large uncertainty in model simulated responses. Here we show that the inter-simulation differences in the global monsoon drying response primarily relate to diverse El Niño responses to tropical eruptions. Most of the coupled climate models simulate El Niño-like equatorial eastern Pacific warming after volcanic eruptions but with different amplitudes across model simulations, which drives a large spread of summer monsoon weakening and corresponding precipitation reduction. Further, two factors are identified for the diverse El Niño responses: the imposed volcanic forcing and the pre-eruption ocean state. Different volcanic forcings are found to induce large systematic differences in the Maritime Continent drying, which induces different levels of westerly winds over equatorial western to central Pacific and subsequent El Niño intensity. The equatorial western Pacific warm water volume in the pre-eruption month also contributes to the diverse El Niño development in the framework of the recharge oscillator mechanism. The two factors explain about 43% of the inter-simulation spread in El Niño responses. This identification of sources of uncertainty in the hydrologic responses to volcanic eruptions has important implications for assessing the side effect of geoengineering as well as improving decadal predictions.