Comparison of diurnal warming estimates from unpumped Argo data and SEVIRI satellite observations

Estimates of diurnal warming at the ocean surface from modified Argo floats providing unpumped measurements of temperature up to the surface are compared against collocated satellite-derived values from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) flying on the METEOSAT-9 Second Generation (MSG) geostationary satellite. The amplitude of diurnal warming is computed from the difference between subskin and foundation temperature estimates derived independently from the Argo and SEVIRI data. The results demonstrate remarkable consistency between the observations, lending support for both products and the associated methodologies, particularly for the estimation of the foundation temperature. Individual subskin values agree to within an absolute mean difference of ≤ 0.1 K and standard deviations of the differences are < 0.4 K. Statistics for comparison of the foundation temperatures are similar. Differences between the corresponding derived estimates of diurnal warming have negligible bias and standard deviations < 0.25 K. The strong agreement of the diurnal warming estimates exists even when excluding nearly isothermal profiles, suggesting the differences are robust to small spatial offsets and point-to-pixel differences. The results particularly support the ability of the modified Argo floats to provide reliable, and highly valuable, measurements of the near-surface temperature, helping to argue for more modified floats. Moreover, the results suggest that the unpumped Argo data has the potential to provide an independent estimate of the foundation temperature for validation of SST analyses. The method for estimating the foundation temperature from SEVIRI represents a good compromise between data coverage and influences of cloud contamination and nighttime cooling.