Ocean Science
www.ocean-sci.net
1812-0784
1812-0792
2
2
2006
10.5194/os-2-97-2006
http://www.ocean-sci.net/2/97/2006/
http://www.ocean-sci.net/2/97/2006/os-2-97-2006.html
http://www.ocean-sci.net/2/97/2006/os-2-97-2006.pdf
97
112
2006-08-30
The assessment of temperature and salinity sampling strategies in the Mediterranean Sea: idealized and real cases
F. Raicich
fabio.raicich@ts.ismar.cnr.it
CNR, Istituto di Scienze Marine, viale Romolo Gessi 2, 34123 Trieste, Italy
Temperature and salinity sampling strategies are studied and compared by
means of the Observing System Simulation Experiment technique in order to
assess their usefulness for data assimilation in the framework of the
Mediterranean Forecasting System. Their impact in a Mediterranean General
Circulation Model is quantified in numerical twin experiments via bivariate
data assimilation of temperature and salinity profiles in summer and winter
conditions, using the optimal interpolation algorithm implemented in the
System for Ocean Forecasting and Analysis. The data impact is quantified by
the error reduction in the assimilation run relative to the free run.
<P>
The sampling strategies studied here include various combinations of
temperature and salinity profiles collected along Volunteer Observing Ship
(VOS) tracks, by Mediterranean Multi-sensor Moored Arrays (M3A), a Glider
and ARGO floating profilers. Idealized sampling strategies involving VOS
data allow to recognize the impact of individual tracks. As a result, the
most effective tracks are those crossing regions characterized by high
mesoscale variability and the presence of frontal structures between water
masses.
<P>
Sampling strategies adopted in summer–autumn 2004 and winter 2005 are
studied to assess the impact of VOS and ARGO data in real conditions. The
combination of all available data allows to achieve up to 30% error
reductions. ARGO data produce a small impact when alone, but represent the
only continuous coverage of the basin and are useful as a complement to VOS
data sets.
<P>
Localized data sets, as those obtained by M3As and the Glider, seem to have
an almost negligible impact in the basin-scale assessment, and are expected
to be more effective at regional scale.
Arnold Jr., C. P. and Dey, C. H.: Observing-system simulation experiments: Past, present and future, Bull. Am. Meteor. Soc., 67, 687–695, 1986.
Barth, N. and Wunsch, C.: Oceanographic experiment design by simulated annealing, J. Phys. Oceanogr., 20, 1249–1263, 1990.
Bennett, A. F.: Inverse methods for assessing ship-of-opportunity networks and estimating circulation and winds from tropical expendable bathythermograph data, J. Geophys. Res., 95, 16 111–16 148, 1990.
Brankart, J.-M. and Pinardi, N.: Abrupt cooling of the Mediterranean Levantine Intermediate Water at the beginning of the eighties: observational evidence and model simulation, J. Phys. Oceanogr., 31, 2307–2320, 2001.
Brasseur, P., Beckers, J.-M., Brankart, J.-M., and Schoenauen, R.: Seasonal temperature and salinity fields in the Mediterranean Sea: Climatological analyses of an historical data set, Deep-Sea Res., 43, 159–192, 1996.
Castellari, S., Pinardi, N., and Leaman, K.: A model study of air-sea interactions in the Mediterranean Sea, J. Mar. Syst., 18, 89–114, 1998.
Castellari, S., Pinardi, N., and Leaman, K.: Simulation of water mass formation processes in the Mediterranean Sea: influence of the time frequency of the atmospheric forcing, J. Geophys. Res., 105, 24 157–24 181, 2000.
De Mey, P.: Optimal interpolation in a model of the Azores current in 1986–88, in: Data assimilation: Tools for modelling the ocean in a global perspective, NATO/ASI Series, I/19, edited by: Brasseur, P. P. and Nihoul, J. C. J., Springer-Verlag, 253 pp, 1994.
De Mey, P.: Data assimilation at the oceanic mesoscale: A Review, J. Meteorol. Soc. Japan, 75, Special issue on "Data assimilation in meteorology and oceanography: Theory and practice", 415–427, 1997.
De Mey, P. and Benkiran, M.: A multivariate reduced-order optimal interpolation method and its application to the Mediterranean basin-scale circulation, in: Ocean Forecasting Conceptual Basis and Applications, edited by: Pinardi, N. and Woods, J., Springer-Verlag, 281–306, 2002.
Demirov, E. and Pinardi, N.: Simulation of the Mediterranean Sea circulation from 1979 to 1993: Part I. The interannual variability, J. Mar. Syst., 33–34, 23–50, 2002.
Demirov, E., Pinardi, N., Fratianni, C., Tonani, M., Giacomelli, L., and De Mey, P.: Assimilation scheme of Mediterranean Forecasting System: Operational implementation, Ann. Geophys., 21, 189–204, 2003.
Derber, J. and Rosati, A.: A global oceanic data assimilation scheme, J. Phys. Oceanogr., 19, 1333–1347, 1989.
Fichaut, M., Balopoulos, E., Dooley, H., García-Fernandez, M.-J., Iona, A., Jourdan, D., Baudet, L., and Maillard, C.: A common protocol to assemble a coherent database from distributed heterogeneous data sets: The MEDATLAS database experience, in: Marine science and technology programme: Experiences in project data management, edited by: Bohle-Carbonell, M., European Commission, Luxembourg, 349 pp, 1998.
Griffa, A., Molcard, A., Raicich, F., and Rupolo, V.: Assessment of the impact of TS assimilation from ARGO floats in the Mediterranean Sea, Ocean Sci. Discuss., 3, 671–700, 2006.
Guinehut, S., Larnicol, G., and Le Traon, P.-Y.: Design of an array of profiling floats in the North Atlantic from model simulations, J. Mar. Syst., 35, 1–9, 2002.
Guinehut, S., Le Traon, P.-Y., Larnicol, G., and Philipps, S.: Combining Argo and remote-sensing data to estimate the ocean three-dimensional temperature fields – A first approach based on simulated observations, J. Mar. Syst., 46, 85–98, 2004.
Hackert, E. C., Miller, R. N., and Busalacchi, A. J.: An optimized design for a moored instrument array in the tropical Atlantic Ocean, J. Geophys. Res., 103, 7491–7509, 1998.
Hernandez, F., Le Traon, P.-Y., and Barth, N. H.: Optimizing a drifter cast strategy with a genetic algorithm, J. Atmos. Ocean. Tech., 12, 330–345, 1994.
Kindle, J. C.: Sampling strategies and model assimilation of altimetric data for ocean monitoring and prediction, J. Geophys. Res., 91, 2418–2432, 1986.
Korres, G., Pinardi, N., and Lascaratos, A.: The ocean response to low-frequency interannual atmospheric variability in the Mediterranean Sea. Part I: sensitivity experiments and energy analysis, J. Climate, 13, 705–731, 2000.
LeTraon, P.-Y. and Ogor, F.: ERS-1/2 orbit improvement using Topex/Poseidon: the 2 cm challenge, J. Geophys. Res., 103, 8045–8050, 1998.
Malanotte-Rizzoli, P., Manca, B. B., Ribera d'Alcalà, M., Theocharis, A., Brenner, S., Budillon, G., and Özsöy, E.: The Eastern Mediterranean in the 80s and in the 90s: the big transition in the intermediate and deep circulations, Dyn. Atmos. Oceans, 29, 365–395, 1999.
Manzella, G. M. R., Scoccimarro, E., Pinardi, N., and Tonani, M.: Improved near-real time management procedures for the Mediterranean ocean Forecasting System – Voluntary Observing Ship program, Ann. Geophys., 21, 49–62, 2003.
Millot, C.: Circulation in the Western Mediterranean Sea, J. Mar. Syst., 20, 423–442, 1999.
Miyakoda, K., Smagorinsky, J., Strickler, R. F., and Hembree, G. D.: Experimental extended predictions with a nine-level hemispheric model, Mon. Wea. Rev., 97, 1–76, 1969.
Nittis, K., Tziavos, C., Thanos, I., Drakopoulos, P., Cardin, V., Ga\vci\'c, M., Petihakis, G., and Basana, R.: The Mediterranean Moored Multi-sensor Array (M3A): system development and initial results, Ann. Geophys., 21, 75–87, 2003.
Özsöy, E., Hecht, A., Ünlüata, Ü., Brenner, S., Sur, S., Bishop, H. I., Latif, M. A., Rosentroub, Z., and O\uguz, T.: A synthesis of the Levantine Basin circulation and hydrography, 1985–1990, Deep-Sea Res., Part II, 40, 1075–1119, 1993.
Pacanowski, R. C., Dixon, K., and Rosati, A.: The GFDL Modular Ocean Model users guide, version 1.0, Geophysical Fluid Dynamics Laboratory Ocean Tech. Rep. 2, 18 pp, 1990.
Poulain, P.-M.: A profiling float program in the Mediterranean, Argonautics, 6, 2, 2005.
Pinardi, N. and Flemming, N. C. (Eds.): The Mediterranean Forecasting System Science Plan, EuroGOOS Publication No. 11, Southampton Oceanographic Centre, Southampton, UK, 52 pp, 1998.
Raicich, F. and Rampazzo, A.: Observing System Simulation Experiments for the assessment of temperature sampling strategies in the Mediterranean Sea, Ann. Geophys., 21, 151–165, 2003.
Rohaly, G. D. and Krishnamurti, I. N.: An observing system simulation experiment for the Laser Atmospheric Wind Sounder (LAWS), J. Appl. Meteorol., 32, 1453–1471, 1993.
She, J., Høyer, J. L., and Larsen, J.: Assessment of sea surface temperature observational networks in the Baltic Sea and North Sea, J. Mar. Syst., Special Issue "Marine Environmental Monitoring and Prediction", in press, 2006.
Sparnocchia, S., Pinardi, N., and Demirov, E.: Multivariate Empirical Orthogonal Function analysis of the upper thermocline structure of the Mediterranean Sea from observations and model simulations, Ann. Geophys., 21, 167–187, 2003.
Taillandier, V., Griffa, A., Poulain, P.-M., and Béranger, K.: Assimilation of Argo float positions in the north western Mediterranean Sea and impact on ocean circulation simulations, Geophys. Res. Lett., 33, L11604, doi:10.1029/2005GL025552, 2006.