The Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRn oceaN (CAPRICORN) experiment was carried out in March-April 2016 onboard the R/V Investigator studying the momentum (τ), sensible (H_s) and latent (H_l) heat fluxes over the Australian sector of the Southern Ocean including over one cyclonic cold-core and one anticyclonic warm-core mesoscale oceanic eddy. The direct flux measurements obtained with the NOAA PSD flux system are compared with those obtained by the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.5 bulk model and neutral transfer coefficients are studied. We find that while 10-m neutral drag and latent-heat transfer coefficients depend linearly on the magnitude of the mean 10-m wind vector (U_10n) for >4 ms^-1, they exhibit no linear correlation with wind-sea (γ_w) or full sea significant wave height (γ). The root mean square (RMS) uncertainties in COARE 3.5 estimates of τ, H_s and H_l are 25%, 73% and 24% respectively with mean biases of 7%, 30%, and 12%. Further, the variability in COARE 3.5 bulk fluxes is investigated with respect to wind-wave conditions, oceanic eddies, precipitation events and extratropical cyclones encountered during the voyage. The main observed variability is an increase in γ_w (∼35%), τ (∼85%), H_s + H_l (∼52%) over the warm eddy as compared to average voyage values. During the passage of 9 extratropical cyclones, an increase in τ (∼55% average) and a decrease in H_s (∼117%) and H_l (∼64%) is noted in the warm sector, compared to pre-storm conditions, but the pattern reverses behind the cold front.

These observations are then employed to evaluate fluxes obtained by European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis product (ERA-Interim), the Australian Integrated Marine Observing System (IMOS) routine observations and Objectively Analyzed air-sea heat Fluxes (OAFlux) project hybrid dataset is performed.