The influences of El Nino and Arctic sea-ice on the QBO disruption in February 2016

The westerly phase of the quasi-biennial oscillation (QBO) was unexpectedly disrupted by an anomalous easterly near 40 hPa (~23 km) in February 2016. At the same time, a very strong El Nino and a very low Arctic sea-ice concentration in the Barents and Kara Sea were present. Previous studies have shown that the disruption of the QBO was primarily caused by the momentum transport of the atmospheric waves in the Northern Hemisphere. Our results indicate that the tropical waves evident over the Atlantic, Africa, and the western Pacific were associated with extratropical disturbances. Moreover, we suggest that the El Nino and sea-ice anomalies in 2016 account for approximately half of the disturbances and waves based on multiple regression analysis of the observational/reanalysis data and large-ensemble experiments using an atmospheric global climate model. Climate science: El Nino and sea-ice impacts on stratosphere The El Nino and sea-ice anomalies in February 2016 were associated with the QBO disruption in 2016 through stratospheric wave anomaly. In early 2016, unprecedented behavior of the quasi-biennial oscillation (QBO), the dominant mode of stratospheric variability with a period of 22–36 months, was observed. Multiple regression analyses of the observational/reanalysis data and the large-ensemble experiments using an atmospheric climate model showed that about half of the waves were associated with the strong El Nino and the reduced Arctic sea-ice in 2016. These results suggest an importance of stratosphere-troposphere coupling process for the QBO anomaly and also for the seasonal forecasts. Similar QBO disruptions may occur more frequently in the future warm climate with the decreasing Arctic sea-ice and possible variation of the El Nino.