Satellite-based datasets of surface turbulent fluxes over the global oceans are being evaluated and improved.O cean surface fluxes of heat, moisture, and momentum observed during field experiments show strong variability on temporal scales that range from the diurnal cycle to the life cycle of storms, and on spatial scales as small as that of an individual convective cloud. High-frequency variability (e.g., diurnal, storm scale) in tropical air-sea fluxes has been hypothesized to influence intraseasonal and interannual variability of the monsoon (e.g., Webster et al. 1998) and the Pacific Ocean warm pool and El Nino (e.g., Sui and Lau 1997;Fasullo and Webster 2000). At high latitudes, large variations in surface fluxes and sea surface temperature are seen in response to storms, which impact the temperature, density, and mixing in the upper ocean, further influencing the atmospheric dynamics and thermodynamics. Storm-scale events have been hypothesized (e.g., Marshall et al. 1998;Nardelli and Salusti 2000) to be associated with ocean convection in the high-latitude water mass formation regions, contributing to deep water formation and the global ocean thermohaline circulation. Ocean mixing induced by tropical cyclones might play an important role in driving the global ocean thermohaline circulation and, thereby,

A field experiment in the southwesternIndian Ocean provides new insights into ocean-atmosphere interactions in a key climatic region. W hile easterly trade winds blow year-round over the southern Indian Ocean, surface winds experience a striking reversal north of 10°S. During boreal summer, the low-level easterly flow penetrates northward, is deflected when crossing the equator, and forms the strong Indian monsoon jet. During boreal winter, northeasterly winds also bend while crossing the equator southward and form a weak low-level westerly jet between the equator and 10°S (Fig. la)

Five satellite products of latent heat flux at the sea surface were compared to bulk fluxes calculated with data from 75 moored buoys, on almost 36 successive months from 1998 to 2000. The five products compared are the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Dataset (HOAPS-2), the Japanese Ocean Flux Datasets with Use of Remote Sensing Observations (J-OFURO), the Jones dataset, the Goddard Satellite-Based Surface Turbulent Fluxes, version 2 (GSSTF-2), and the Bourras-Eymard-Liu dataset (BEL). The comparisons were performed under tropical and midlatitude environmental conditions, with three datasets based on 66 Tropical Atmosphere-Ocean array (TAO) buoys in the tropical Pacific, nine National Data Buoy Center (NDBC) buoys off the U.S. coasts, and four Met Office/Météo-France (UK-MF) moorings west of the United Kingdom and France, respectively. The satellite products did not all compare well to surface data. However, for each in situ dataset (TAO, NDBC, or UK-MF) at least one satellite product was found that had a good fit to surface data, that is, an rms deviation of 15-30 W m Ϫ2 . It was found that HOAPS-2, J-OFURO, GSSTF-2, and BEL satellite products had moderate systematic errors with respect to surface data, from Ϫ13 to 26 W m Ϫ2 , and small biases at midlatitudes (6-8 W m Ϫ2 ). Most of the satellite products were able to render the seasonal cycle of the latent heat flux calculated with surface data. The estimation of near-surface specific humidity was found to be problematic in most products, but it was best estimated in the HOAPS-2 product. GSSTF-2 and J-OFURO strongly overestimated the surface flux variations in time and space compared to surface data and to a flux climatology. With respect to TAO data, Jones fluxes yielded good results in terms of rms deviation (27 W m Ϫ2 ) but also presented a large systematic deviation. Overall, for application of the satellite fluxes to the world oceans, it was found that HOAPS-2 was the most appropriate product, whereas for application to the Tropics, BEL fluxes had the best performance in rms with respect to TAO data (24 W m Ϫ2 ).

The water vapour isotopic composition (1H216O, H218O and 1H2H16O) of the Atlantic marine boundary layer has been measured from 5 research vessels between 2012 and 2015. Using laser spectroscopy analysers, measurements have been carried out continuously on samples collected 10–20 meter above sea level. All the datasets have been carefully calibrated against the international VSMOW-SLAP scale following the same protocol to build a homogeneous dataset covering the Atlantic Ocean between 4°S to 63°N. In addition, standard meteorological variables have been measured continuously, including sea surface temperatures using calibrated Thermo-Salinograph for most cruises. All calibrated observations are provided with 15-minute resolution. We also provide 6-hourly data to allow easier comparisons with simulations from the isotope-enabled Global Circulation Models. In addition, backwards trajectories from the HYSPLIT model are supplied every 6-hours for the position of our measurements.