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Madden-Julian Oscilation Output

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Influence of the MJO on the European region

The Madden-Julian Oscillation (MJO) is a broad-scale wave-like convective phenomena centred on the equator and also the main source of tropical predictability on the monthly time scale.  It is important as it identifies where tropical deep convection interacts with the general atmospheric circulation, and it is observed mainly in a sector spanning the Indian and Pacific oceans.  The feature is typically initiated over the Indian Ocean, and usually advances steadily eastwards, as areas of relatively organised convection, bringing a significant enhancement of rainfall, followed in their wake by much less active convection.  The MJO may be monitored using a combination of lower and upper tropospheric zonal flow patterns and out-going long wave radiation (OLR) or simulations thereof.Image Removed Fig8.2.5-1: Schematic representation of the global teleconnection patterns associated with the Madden-Julian Oscillation (MJO).

The Madden-Julian Oscillation affects the North Atlantic Oscillation.   The mid-latitude jet streams in turn can affect the flow over the North Atlantic which has a strong impact on the tracking of depressions (e.g. towards Europe).  The cross-Atlantic flow can be categorised as positive or negative phases or regimes of the North Atlantic Oscillation (NAO).

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Fig8.2.5-1: Schematic representation of the global teleconnection patterns associated with the Madden-Julian Oscillation (MJO).

Fig8.2.5-2: Schematic diagram of the effects of positive NAO and negative NAO phases in the European and Mediterranean areas.  Positive NAO phase tends to steer depressions towards Northern Europe bringing wetter conditions while the Mediterranean region tends to be drier.  Negative NAO phase tends to steer depressions towards Southern Europe bringing wetter conditions while Northern Europe tends to be drier. 

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