Monday, 26 June 2017
Salon A-E (Marriott Portland Downtown Waterfront)
We compare the different characteristics of extratropical ozone variability related to the Madden-Julian Oscillation (MJO) in the upper troposphere-lower stratosphere (UTLS) in El Niño and La Niña winters using ERA-Interim reanalysis data. Negative/positive ozone anomalies, which associated with anticyclonic/cyclonic anomalies, propagate eastward from the west of Tibetan Plateau to northwest Pacific as the enhanced/suppressed MJO convection propagate from Indian Ocean to Pacific. The negative MJO-related ozone anomalies are stronger in La Niña winters than in El Niño winters when they are over East Asia, but they become weaker in La Niña winters after they propagate to northwest Pacific. On the other hand, the positive MJO-related ozone anomalies over East Asia are more significant in El Niño winters which then become stronger in La Niña winters when they propagate to east coast of China and northwest Pacific. These differences are related to the positive correlation between sea surface temperature (SST) and the strength of the MJO in the Indian Ocean and the western Pacific in winters.
Positive correlation between SST and MJO-related OLR anomalies has been found exist over eastern Indian Ocean and southwestern Pacific. As a result, negative SST anomalies in eastern Indian Ocean in La Niña winters lead to smaller OLR anomalies (stronger negative OLR anomalies in Phases 2-5 and weaker positive OLR anomalies in Phases 6-1) which generate more significant negative ozone anomalies or weaker positive ozone anomalies over East Asia. However as enhanced/suppressed MJO convection propagate to southwest Pacific, opposite SST anomalies compared to eastern Indian Ocean make the relative strength of MJO-related OLR anomalies between El Niño and La Niña reverse, as well as extratropical MJO-related ozone anomalies in UTLS. As the decay of MJO along its eastward journey, the correlation between MJO-related OLR anomalies and SST is much weaker in southwest Pacific than in eastern Indian Ocean.
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