Special seminar: The Atlantic/Pacific atmospheric moisture budget asymmetry

The contrast between basin-integrated precipitation minus evaporation (P-E) of the Atlantic and Pacific Oceans is about 0.4 Sv (1 Sv = 109 kg s-1). The Atlantic is net evaporative and the Pacific near neutral – a result consistent across datasets. This asymmetry is linked to the higher sea surface salinity in the Atlantic than in the Pacific (at all latitudes) and the absence of a deep-water formation in the Pacific.

Here, I will discuss the relationship between the inter-basin P-E contrast and the atmospheric moisture transports. First, it will be shown that the P-E asymmetry is primarily a result of greater Pacific precipitation (notably south of 30oN) rather than greater evaporation over the Atlantic.

The combined analysis of atmospheric moisture fluxes across the catchment boundaries of the basins and moisture-tracking Lagrangian technique further reveals that the eastward moisture flux across South-East Asia, rather the often-invoked flux across Central America, is the key to the P-E asymmetry. The anomalous flux across South-East Asia (i.e. contrasting with the westward flux found in other basins at the same latitudes) is related to the Somali low-level jet and Asian Summer Monsoon. These circulation patterns, diverting trajectories away from Africa into the westerly flow towards the Pacific, explain the higher efficiency of the moisture import to the Pacific than to the Atlantic/Indian basins.

These results highlight the importance of continental geometry and steady large-scale circulation features in the Atlantic/Pacific P-E asymmetry. Implications for future climate change and paleoclimate applications will be discussed.




15:15 h


Bundesstr. 53, room 101/102
Seminar Room 101/102, 1st floor, Bundesstr. 53, 20146 Hamburg, Hamburg


David Ferreira, University of Reading


Roberta D'Agostino

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