Direct measurements of infrared budget and meteorological parameters at sea were carried out in the western Mediterranean Sea during different seasons in the years 1989-1992. The spatial and time distribution of this data set allows us to perform an exhaustive test on the most widely used infrared budget bulk formulas. An underestimation of about 30 W/m 2 is systematically observed, confirming previous results obtained by a limited data set. This discrepancy is independent of the time of the year and location of measurements, indicating an inability of the bulk formulas to reproduce the infrared Mediterranean budget. The completeness of the data set enables us to determine a new relation between infrared budget and meteorological parameters. Alternative expressions, to be used accordingly with the available data sets, are presented here.

Abstract. Meteorological and sea temperature data from the ODAS Italia 1 buoy (Ligurian Sea, Western Mediterranean) are used to study the anomalous warming of summer 2003 at sea. The event was related to the record heat wave that interested much of Europe from June to September of that year. The data show that the anomalous warming was prevalently confined to within a few meters below the sea surface. On the contrary, the temperatures in the underlying layers were lower than usual. The limited vertical propagation of heat is ascribed to the high temperature difference that arose between the surface and the deeper layers due to protracted calm weather conditions. The degree of penetration of heat deduced from the observations is consistent with that computed on the basis of an energetic argument, wherein the wind constitutes the sole supply of kinetic energy, while the heating is viewed as the source of potential energy that must be "subtracted" by mixing. The results support the hypothesis that the scanty energy from the wind is mainly responsible for the development of the temperature anomaly at the sea surface.

No abstract

Direct measurements of solar radiation at sea were carried out in the Western Mediterranean Sea during several cruises in the years 1989-1994. The data collected were used to perform a test on the empirical formula proposed by Reed [1977]. The agreement between measured and empirical data is noteworthy, taking into account the coarseness of the formula. Nevertheless, Reed's estimates show a bias of about 5 W m -2. In order to investigate the causes of this bias, the data were analyzed according to the time of year and the cloud cover index. The results reveal that the computed insolation is overestimated under clear sky conditions and underestimated for cloudy sky. The disagreement of clear sky predictions can be ascribed to a regional misevaluation of both aerosols and water vapor attenuation. The inadequacy of the cloud cover index is indicated to explain the discrepancy of the estimates under cloudy sky. In any case, the mean difference between observations and formula is very slight, and this supports the use of this type of formula to compute long time average insolation over the sea.

Abstract. Three years of 300 kHz acoustic doppler current profiler data collected in the central Ligurian Sea are analysed to investigate the variability of the zooplankton biomass and the diel vertical migration in the upper thermocline. After a pre-processing phase aimed at avoiding the slant range attenuation, hourly volume backscattering strength time series are obtained. Despite the lack of concurrent net samples collection, different migration patterns are identified and their temporal variability examined by means of time-frequency analysis. The effect of changes in the environmental condition is also investigated. The highest zooplankton biomasses are observed in April-May just after the peak of surface primary production in March-April. The main migration pattern found here points to a "nocturnal" migration, with zooplankton organisms occurring deeper in the water column during the day and shallower at night. Also, twilight migration is highlighted during this study. The largest migrations are recorded in November-December, corresponding to lowest backscattering strength values and they are likely attributable to larger and more active organisms (i.e. euphausiids and mesopelagic fish). The results suggest further applications of the available historical acoustic doppler current profiler time series.