Global land surface temperature (LST) data derived from satellite-based infrared radiance measurements are highly valuable for various applications in climate research. While in situ validation of satellite LST data sets is a challenging task, it is needed to obtain quantitative information on their accuracy. In the standardised approach to multi-sensor validation presented here for the first time, LST data sets obtained with state-of-the-art retrieval algorithms from several sensors (AATSR, GOES, MODIS, and SEVIRI) are matched spatially and temporally with multiple years of in situ data from globally distributed stations representing various land cover types in a consistent manner. Commonality of treatment is essential for the approach: all satellite data sets are projected to the same spatial grid, and transformed into a common harmonized format, thereby allowing comparison with in situ data to be undertaken with the same methodology and data processing. The large data base of standardised satellite LST provided by the European Space Agency’s GlobTemperature project makes previously difficult to perform LST studies and applications more feasible and easier to implement. The satellite data sets are validated over either three or ten years, depending on data availability. Average accuracies over the whole time span are generally within ±2.0 K during night, and within ± 4.0 K during day. Time series analyses over individual stations reveal seasonal cycles. They stem, depending on the station, from surface anisotropy, topography, or heterogeneous land cover. The results demonstrate the maturity of the LST products, but also highlight the need to carefully consider their temporal and spatial properties when using them for scientific purposes.

[1] The surface circulation and eddy field from the Azores Current system are studied here by analyzing surface drifters records and altimetry maps collected over more than 16 years. Clear differences in mean flow and eddy characteristics allow for a classification of the Azores Current in three zonal sectors: west of 30°W between the Mid-Atlantic Ridge and the Hyères-Atlantis seamount system, between 30°W and the longitude of Madeira, and east of Madeira. A detailed and quantitative characterization of each sector is given. The transition between the western and central parts is controlled by the Hyères-Atlantis ridge. In the transition to the eastern sector there is a change in the dynamics and the flow is forced by the cyclonic recirculation driven by the Mediterranean outflow. There is no clear expression of a continuous surface northern counterflow, but three distinct westward flows are seen: one along the southeastern border of the Azores plateau, another one southwest of Madeira, and a third one along 31°N west of the Hyères seamount. No clear tilt in the axis of the Azores Current is found in the calculated mean surface flow from surface drifters. Observations from both drifters and altimetry data show that anticyclonic features dominate in the northern region, whereas cyclonic ones dominate in the southern region. Overall, cyclones are more numerous, constituting 60% of large eddies. The eddy features detected in the west tend to be larger than those in the east, both in size and sea level anomaly. There is indication of different mean propagation speeds east and west of 25°W-30°W, with the mean speeds consistently increasing by 25%-45% in the west. Estimates for the rate of formation of strong eddies range from 1.4 to 2.4 year −1 for cyclones, and 1.2 to 1.7 year −1 for anticyclones.

This study presents the results of a multidisciplinary approach, using hydrogeochemical, isotopic and ecotoxicological analyses, performed to assess the nature and suitability for use of Paranhos and Salgueiros spring waters (Porto city, NW Portugal). Based on the surface activities located along the course of the springs, 23 water samples were collected. All the samples were analysed for major element concentrations. The isotopic techniques employed included d 2 H, d 18 O and 3 H. Standard acute bioassays with Daphnia magna were also performed. The hydrogeochemical analyses showed a nitrate and sulphateenriched composition for these groundwaters, resulting mainly from urban drainage and sewer leakage. In the ecotoxicological analyses, no significant mortality was observed in any of the tests performed. The results obtained in this study suggest that Porto urban groundwater could be suitable for irrigation uses.

International audienceThe mean seasonal hydrography and circulation of the Western Iberian Margin (WIM) are studied by means of a high-resolution configuration of the Regional Oceanic Modeling System. A comparison of 5-year model averages for January and July with climatological datasets shows a general good agreement in the reproduction of the mean water mass properties and hydrographic distribution. We find that there is a prevailing tendency for slope poleward flow at about 80 – 100 km offshore at all latitudes from the surface to 1,500 m with strong vertical coupling. This northward flow, which is mainly along slope and amounts up to 8 – 10 cm s1, exhibits several mean flow recirculation regions on its way and evidences of an offshore pathway of poleward flow. Transports at different zonal sections further confirm the poleward flow tendency with two peaks of poleward transport in summer (3 –10 Sv) and winter (2 – 7 Sv). The transport time series emphasize the seasonal character of the alongshore circulation and the interannualintrinsic variability ofthe circulation,since the forcing fields are climatological. As a conceptual essay with the purpose of assessing the Mediterranean Water flow influence on the WIM mean circulation, a second model configuration is setup, where the Mediterranean outflow into the study domain is removed. We find that there is an attenuation of the mesoscale field, but the slope poleward flow intensifies and remains as a mean dynamical feature closer to the upper slope