Air-Sea Interaction and Diurnal Variability in Tropical Oceans

Air–sea interaction in tropical oceans encompasses the exchange of heat, momentum and gases across the ocean surface, driven by solar radiation, wind stress and ocean mixing. Diurnal variability in sea surface temperature (SST) and surface fluxes modulates atmospheric convection, cloud formation and boundary-layer processes on hourly to daily timescales. In the tropics, calm wind conditions often lead to strong daytime warming of the upper ocean, which in turn enhances afternoon turbulence and moisture flux into the atmosphere. These sub-daily interactions underpin larger-scale phenomena such as the Madden–Julian oscillation (MJO) and the El Niño–Southern Oscillation (ENSO), and influence regional rainfall patterns, tropical cyclone genesis and marine biogeochemistry. Improved understanding of these processes is vital for weather forecasting, climate modelling and the assessment of ocean carbon uptake.

Research from Nature Portfolio

Recent studies have highlighted the role of upper-ocean thermal memory in modulating successive convective pulses of the MJO. Observations of ocean response to sequential wind bursts reveal persistent subsurface mixing and currents that deplete heat energy available for later pulses, producing a feedback whereby weak pulses tend to be followed by stronger events and vice versa. This memory effect implies that ocean mixing and heat redistribution on intraseasonal timescales are key to the predictability and amplitude modulation of tropical convective disturbances.

Air-Sea Interaction and Diurnal Variability in Tropical Oceans publication trend

The graph below shows the total number of articles in air-sea interaction and diurnal variability in tropical oceans across all publications each year (not limited to Nature Index journals).

Technical terms

Air–sea interaction: Exchange of momentum, heat and gases between the atmosphere and the ocean surface.

Diurnal variability: Fluctuations in physical quantities (such as SST) over the course of a day, driven by the solar cycle and atmospheric conditions.

Sea surface temperature (SST) diurnal amplitude: The difference between maximum and minimum SST within a 24-hour period.

Madden–Julian oscillation (MJO): A 30–70-day tropical convective system characterised by eastward-propagating rainfall and atmospheric circulation anomalies.

El Niño–Southern Oscillation (ENSO): The dominant mode of interannual climate variability in the tropical Pacific, comprising warm (El Niño) and cold (La Niña) phases.

Ocean mixed layer: The uppermost ocean layer where temperature and salinity are homogenised by wind and buoyancy-driven mixing.

References

1. Key to ENSO phase-locking simulation: effects of sea surface temperature diurnal amplitude. npj Climate and Atmospheric Science (2023).
2. Improved Atmosphere‐Ocean Coupled Simulation by Parameterizing Sub‐Diurnal Scale Air‐Sea Interactions. Journal of Advances in Modeling Earth Systems (2024).
3. Ocean feedback to pulses of the Madden–Julian Oscillation in the equatorial Indian Ocean. Nature Communications (2016).
4. The impact of diurnal variability in sea surface temperature on the central Atlantic air-sea CO2 flux. Atmospheric Chemistry and Physics (2009).
5. Diurnal Ocean Surface Warming Drives Convective Turbulence and Clouds in the Atmosphere. Geophysical Research Letters (2021).