| 09 Sep 2026
The influence of the Madden-Julian Oscillation and extratropical Rossby wave dynamics on daily to multi-day precipitation variability in the arid Middle East during the wet season
Abstract. Most of the annual precipitation in the arid Middle East falls on only a few days per year during the cool season, having important implications for water resources and hydrometeorological hazards. Previous studies have shown that daily precipitation in the Middle East is modulated by both intraseasonal variability in tropical convection related to the Madden-Julian Oscillation (MJO) and midlatitude Rossby wave dynamics. However, their respective contributions to precipitation variability and their underlying mechanisms remain largely unexplored. This study quantifies the separate and joint influence of the MJO and midlatitude Rossby wave dynamics on daily to multi-day precipitation variability in the arid Middle East during the wet season (November–April) and explores the underlying mechanisms. To this end, we use daily precipitation observations and atmospheric reanalysis data for the period 1979–2020 along with diagnostics of Rossby wave packets and Rossby wave breaking. Our findings indicate that the remote influence of the MJO and local midlatitude Rossby wave forcing operate largely independent of each other and exert an approximately equal influence on Middle Eastern precipitation variability. Consistent with previous studies, reduced (enhanced) tropical convection over the eastern Indian Ocean and Maritime Continent during MJO phases 8 and 1 (4 and 5) increases (decreases) precipitation by more than 50 %. MJO convective activity influences Middle Eastern precipitation through a baroclinic response in the regional tropical circulation, consistent with the Matsuno-Gill model, inducing anomalies in the upper- and lower-tropospheric circulation, in atmospheric moisture transport into the region, and in large-scale vertical motion over the region. The immediate influence of the MJO via the regional tropical circulation does not alter the propagation and breaking of Rossby waves into the region in a manner that is consistent with wet or dry conditions. However, our findings suggest an extratropical pathway through which the MJO modulates precipitation over the Middle East with an approximately two-week lag, extending wet or dry conditions induced by the immediate MJO influence. The concurrence of the MJO with anomalous Rossby wave forcing can amplify or mute the precipitation response that would be expected from midlatitude forcing alone through strengthening or weakening the atmospheric moisture supply and through reinforcing or offsetting large-scale vertical motion over the region. This study contributes to improved process understanding of tropical and extratropical controls on precipitation variability in the water-scarce Middle East with implications for medium-range to sub-seasonal prediction of precipitation and early warnings for drought and flood hazards.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Weather and Climate Dynamics.
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