Monsoonal Variability and Ocean-Atmosphere Interactions

Monsoonal variability arises from the seasonal reversal of prevailing winds and associated shifts in rainfall distribution, driven by differential heating between continents and adjacent oceans. Central to this phenomenon is the coupling between sea surface temperatures, ocean currents and atmospheric circulations such as the Hadley and Walker cells. On intraseasonal timescales, the Madden–Julian Oscillation modulates monsoon onset and active–break cycles, while interannual fluctuations are largely governed by the El Niño–Southern Oscillation and the Tropospheric Biennial Oscillation, which impose alternating wet and dry regimes across monsoon domains. Decadal and multidecadal modes, notably the Interdecadal Pacific Oscillation and the Indian Ocean Dipole, induce longer-term shifts in monsoon strength through their influence on sea surface temperature gradients and thermocline depth. Regional cross-equatorial flows supply moisture from tropical seas into monsoon troughs, with critical sources in the Banda and Solomon seas for the western North Pacific monsoon and in the Somali region for the South Asian system. Teleconnections link remote ocean basins, so that anomalous conditions in the Atlantic or Pacific can modulate rainfall extremes in South Asia, East Asia and Australia. Understanding these ocean–atmosphere feedbacks is essential for improving seasonal forecasts, managing water resources and adapting to climate change impacts on agriculture and ecosystems.

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Recent analyses have documented an interdecadal weakening of cross-equatorial flows over the Maritime Continent during boreal summer, linked to a negative phase of the Interdecadal Pacific Oscillation. Observational reanalyses and coupled model sensitivity experiments reveal that cold central Pacific sea surface temperature anomalies diminish local convection, alter regional Hadley cell patterns and reduce low-level moisture transport into the western North Pacific monsoon system.

Advances in multiscale atmosphere–ocean linkage studies have shown that fundamental and combination modes of ENSO with the annual cycle generate teleconnections between the Pacific and Indian Oceans, driving characteristic sea surface temperature anomalies and Indian Ocean Dipole events. These modes also synchronise tropospheric biennial oscillations and contribute to a west Pacific multidecadal mode, which modulates monsoon variability and precipitation over Australia.

Investigations of the Tropospheric Biennial Oscillation of East Asian summer rainfall demonstrate robust north–south seesaw patterns in China on two-year timescales. Atmospheric model intercomparison runs and observational data confirm that Pacific sea surface temperature anomalies associated with El Niño and La Niña episodes drive alternating wet and dry conditions, with northern China tending towards dryness in El Niño summers and southern China exhibiting the opposite response.

Monsoonal Variability and Ocean-Atmosphere Interactions publication trend

The graph below shows the total number of articles in monsoonal variability and ocean-atmosphere interactions across all publications each year (not limited to Nature Index journals).

Technical terms

Monsoon: Seasonal reversal of wind circulation and associated precipitation changes between land and ocean.

Sea Surface Temperature (SST): Temperature of the ocean’s surface layer, influencing air–sea heat and moisture exchanges.

El Niño–Southern Oscillation (ENSO): Irregular interannual variation of tropical Pacific sea surface temperatures and atmospheric pressure.

Indian Ocean Dipole (IOD): Mode of Indian Ocean climate variability marked by east–west sea surface temperature differences.

Madden–Julian Oscillation (MJO): Intraseasonal eastward-propagating pulse of convective and circulation anomalies across the tropics.

Tropospheric Biennial Oscillation (TBO): Alternating strength of monsoon rainfall on approximately two-year cycles.

Interdecadal Pacific Oscillation (IPO): Multidecadal fluctuation of Pacific basin sea surface temperatures affecting global climate patterns.

References

1. The role of the New Guinea cross-equatorial flow in the interannual variability of the western North Pacific summer monsoon. Environmental Research Letters (2014).
2. Tropospheric biennial oscillation of summer monsoon rainfall over East Asia and its association with ENSO. Climate Dynamics (2014).
3. Interdecadal weakening of the cross-equatorial flows over the Maritime Continent during the boreal summer in the mid-1990s: drivers and physical processes. Climate Dynamics (2021).
4. Indo-Pacific Variability on Seasonal to Multidecadal Timescales. Part II: Multiscale Atmosphere-Ocean Linkages. Journal of Climate (2017).