We investigate the connection between the equatorial Madden‐Julian Oscillation (MJO) and different types of the Northern Hemisphere mid‐winter major stratospheric sudden warmings (SSWs), i.e., vortex‐displacement and vortex‐split SSWs. The MJO‐SSW relationship for vortex‐split SSWs is stronger than that for vortex‐displacement SSWs, as a result of the stronger and more coherent eastward propagating MJOs before vortex‐split SSWs than those before vortex‐displacement SSWs. Composite analysis indicates that both the intensity and propagation features of MJO may influence the MJO‐related circulation pattern at high latitudes and the type of SSWs. A pronounced Quasi‐Biennial Oscillation (QBO) dependence is found for vortex‐displacement and vortex‐split SSWs, with vortex‐displacement (‐split) SSWs occurring preferentially in easterly (westerly) QBO phases. The lagged composites suggest that the MJO‐related anomalies in the Arctic are very likely initiated when the MJO‐related convection is active over the equatorial Indian Ocean (around the MJO phase 3). Further analysis suggests that the QBO may modulate the MJO‐related wave disturbances via its influence on the upper tropospheric subtropical jet. As a result, the MJO‐related circulation pattern in the Arctic tends to be wave number‐one/wave number‐two ~25–30 days following phase 3 (i.e., approximately phases 7–8, when the MJO‐related convection is active over the western Pacific) during easterly/westerly QBO phases, which resembles the circulation pattern associated with vortex‐displacement/vortex‐split SSWs.
A record minimum in total column ozone over the Tibetan Plateau in December 2003 is analyzed using both satellite observations and a chemical transport model (MOZART‐3). Ozone profiles observed by the MIPAS and GOMOS over the ozone minimum region (25°–35°N, 85°–110°E) show pronounced ozone reduction in both the upper troposphere and lower stratosphere (UTLS) and the middle stratosphere regions. MOZART‐3 simulation indicates that ozone reduction in the UTLS region is generally caused by uplift of the local tropopause and northward transport of tropical ozone‐poor air associated with an anomalous anticyclone in the upper troposphere. MIPAS observation suggests that the displacement of “low‐ozone pockets” is responsible for ozone decline in the middle‐stratospheric region and contributes to 29–46% of the total column ozone reduction. Further analysis shows that the upper‐tropospheric anticyclonic anomaly is closely associated with the Rossby‐wave triggered by the eastward propagating Madden–Julian Oscillation convective heating.
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