ALBERT

Beschreibung: In this paper results from the application of an ocean data assimilation (ODA) system, combining a multivariate reduced-order optimal interpolator (OI) scheme with a global ocean general circulation model (OGCM), are described. The present ODA system, designed to assimilate in situ temperature and salinity observations, has been used to produce ocean reanalyses for the 1962–2001 period. The impact of assimilating observed hydrographic data on the ocean mean state and temporal variability is evaluated. A special focus of this work is on the ODA system skill in reproducing a realistic ocean salinity state. Results from a hierarchy of different salinity reanalyses, using varying combinations of assimilated data and background error covariance structures, are described. The impact of the space and time resolution of the background error covariance parameterization on salinity is addressed.

Beschreibung: This work has been funded by the ENACT Project (Contract EVK2-CT2001-00117) for A. Bellucci and P. Di Pietro, and partially by the ENSEMBLES Project (Contract GOCE-CT-2003-505539) for A. Bellucci.

Beschreibung: Published

Beschreibung: 3785-3807

Beschreibung: 3.7. Dinamica del clima e dell'oceano

Beschreibung: JCR Journal

Beschreibung: reserved

Beschreibung: Skill in ensemble-mean dynamical seasonal climate hindcasts with a coupled land-atmosphere model and specified observed sea surface temperature is compared to that for long multi-decade integrations of the same model where the initial conditions are far removed from the seasons of validation. The evaluations are performed for surface temperature and compared among all seasons. Skill is found to be higher in the seasonal simulations than the multi-decadal integrations except during boreal winter. The higher skill is prominent even beyond the first month when the direct influence of the atmospheric initial state elevates model skill. Skill is generally found to be lowest during the winter season for the dynamical seasonal forecasts, equal to that of the long integrations, which show some of the highest skill during winter. The reason for the differences in skill during the non-winter months is attributed to the severe climate drift in the long simulations, manifest through errors in downward fluxes of water and energy over land and evident in soil wetness. The drift presses the land surface to extreme dry or wet states over much of the globe, into a range where there is little sensitivity of evaporation to fluctuations in soil moisture. Thus, the land-atmosphere feedback is suppressed, which appears to lessen the model’s ability to respond correctly over land to remote ocean temperature anomalies.

Beschreibung: Center for Ocean-Land-Atmosphere Studies

Beschreibung: Published

Beschreibung: This report describes calibration techniques developed over the past three years for the WHOI/Brown CTD in the Moored Array Program. Comparison is made with classical methods of hydrography for stations obtained in the MODE-1 density program. Methods for temperature lag correction and conversion of conductivity to salinity are given.

Beschreibung: Prepared for the Office of Naval Research under Contract N00014-74-C0262; NR 083-004.

Beschreibung: Originally issued as Reference No. 59-54

Beschreibung: In August and September 1958 a number of oceanographic sections were made in the R.R.S. DISCOVERY II, Captain James Gray, under the scientific leadership of H. F. P. Herdman. These sections comprise part of a joint program undertaken by the National Institute of Oceanography and the Woods Hole Oceanographic Institution for the International Geophysical Year.

Beschreibung: The United States participation in this program was supported by the Office of Naval Research Contract Nonr 2196(00) with the Woods Hole Oceanographic Institution.

Beschreibung: This report summarizes the work, under the auspices of the WOCE Hydrographic Programme (WHP), which took place on the R/V Akademik Vernadsky in June-July 1991. The goal of the exercise was an international comparison/training cruise to obtain comparisons of water sampling methods and analytical techniques employed by several groups for the oceanographic measurement of salinity and oxygen in seawater. The training aspect was formalized in a pre-cruise practicum held on board the vessel by Dr. Fred Culkin and Mr. Paul Ridout of Ocean Scientific International, the manufacturer of IAPSO Standard Seawater, At-sea comparisons of Russian Reference Water, manufactured in Moscow, were made with IAPSO water. Further work involved comparisons of a Guildline and a pair of SOKOL salinometers using reference water and natural seawater collected on the cruise. While the agreement among the salnometers was quite good and at the level of acceptability for the WHP, it was discovered that lack of thermal equilbration of the salinity samples run on the SOKOLs led to substantial "errors" at large depths (or for cold water samples). This could not have been anticipated before the cruise and would have been missed in a shore-based or laboratory exercise. All five groups making oxygen comparisons benefitted from the technical exchange afforded by the cruise and, as a result of reconciling inter-group differences, have identified procedural changes they wil make in the future in order to achieve the high standards required by the WHP, The technical interaction, which amounted to "training" for all groups, was greatly facilitated by the cooperation of Captain Malnovsky, Chief Scientist Panteleyev, the scientists from MHI, Sevastopol, and the crew of the Vernadsky. On the Vernadsky comparison cruise, a shore-based practicum was held prior to sailing in order to review the theory and measurement of salinity. The cruise itself, which took place between 27 June and 8 July 1991, was in the NE Atlantic to the west of Madeira. An international group of experts in salnity and oxygen measurements was drawn from the United Kingdom (UK), Spain, Russia, Ukraine, and the United States (US). Except for one of the five groups, measured oxygen values in the range of 3-5 mIll (concentration units are used throughout) agreed with one another within :11%, which exceeds the WOCE requirements by a factor of 2. Subsequent analyses of the differences by all five groups could account for much of the observed inter-group variations, Intra-group precision was generally in the range of 0,1-0.4%, As a result, of a low oxygen sparging experiment in which sample oxygens 0: 1.2 mIll were generated, substantial inter-group differences of :1.08 mIll were found indicating that oxygen specifications for WOCE need to be expressed as both a percent "error" and a low oxygen bias. The salinity comparison component of the cruise enabled comparison of various batches of Russian Reference Water (RRW) of various salnities (10, 20, 30, 35 and 40) against IAPSO Standard Seawater (SSW) of various salinities (10, 30, 35 and 38); inferences could then also be drawn on the relative performance of the two types of salinometer (Guildline Autosal 8400 and SOKOL 4602) used during the experiment. Under quasilaboratory conditions, the machines produced mean results different by no more than 0.001 in salinity for salinity 35 RRW, standardizing against salinity 35 SSW. The other salnities produced less conclusive results, but the three salinometers deviated by no more than 0.003 from the expected value over a wide range of salinities. Under operational conditions (analysis of duplicate samples collected from CTD casts) a mean bias emerged between machines of approximately 0.005 in salinity (SOKOL fresher than Guildline), Subsequent investigations tentatively ascribed this bias to non-equilbration of deep (cold) samples in the Russian system.

Beschreibung: Prepared for the National Science Foundation under Grants OCE89-07815, and OCE92-06184, T. Joyce, Principal Investigator; Vetlesen Funds, Woods Hole Oceanographic Institution; and with support from the Intergovernmental Oceanographic Commission.