Validation of FOAM near-surface ocean current forecasts using Lagrangian drifting buoys

Abstract. In this study, the quality of near-surface current forecasts from the FOAM ocean forecasting system is assessed using the trajectories of Lagrangian drifting buoys. A method is presented for deriving pseudo-Eulerian estimates of ocean currents from the positions of Surface Velocity Program drifters and the resulting data are compared to velocities observed by the global tropical moored buoy array. A quantitative analysis of the global FOAM velocities is performed for the period 2007 and 2008 using currents derived from over 3000 unique drifters (providing an average of 650 velocity observations per day). A potential bias is identified in the Southern Ocean which appears to be caused by wind-slip in the drifter dataset as a result of drogue loss. The drifter-derived currents are also used to show how the data assimilation scheme and a recent system upgrade impact upon the quality of FOAM current forecasts.

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Near-surface current and temperature variability observed in the equatorial Atlantic from drifting buoys

Journal of Geophysical Research Atmospheres ◽

10.1029/jc091ic05p06569 ◽

1986 ◽

Vol 91 (C5) ◽

pp. 6569 ◽

Cited By ~ 27

Author(s):

G. Reverdin ◽

M. J. McPhaden

Keyword(s):

Surface Current ◽

Temperature Variability ◽

Equatorial Atlantic ◽

Near Surface ◽

Drifting Buoys

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Near-surface ocean current sensors: Problems and performance

10.1109/ccm.1978.1158389 ◽

2005 ◽

Cited By ~ 14

Author(s):

J. McCullough

Keyword(s):

Ocean Current ◽

Near Surface ◽

Surface Ocean ◽

Current Sensors ◽

And Performance

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Mediterranean Forecasting System: forecast and analysis assessment through skill scores

Ocean Science ◽

10.5194/os-5-649-2009 ◽

2009 ◽

Vol 5 (4) ◽

pp. 649-660 ◽

Cited By ~ 60

Author(s):

M. Tonani ◽

N. Pinardi ◽

C. Fratianni ◽

J. Pistoia ◽

S. Dobricic ◽

...

Keyword(s):

Forecast Error ◽

Skill Score ◽

Skill Scores ◽

Basin Scale ◽

System Variability ◽

Forecasting System ◽

Different Depths ◽

The Difference ◽

Ocean Forecasting

Abstract. This paper describes the first evaluation of the quality of the forecast and analyses produced at the basin scale by the Mediterranean ocean Forecasting System (MFS) (http://gnoo.bo.ingv.it/mfs). The system produces short-term ocean forecasts for the following ten days. Analyses are produced weekly using a daily assimilation cycle. The analyses are compared with independent data from buoys, where available, and with the assimilated data before the data are inserted. In this work we have considered 53 ten days forecasts produced from 16 August 2005 to 15 August 2006. The forecast skill is evaluated by means of root mean square error (rmse) differences, bias and anomaly correlations at different depths for temperature and salinity, computing differences between forecast and analysis, analysis and persistence and forecast and persistence. The Skill Score (SS) is defined as the ratio of the rmse of the difference between analysis and forecast and the rmse of the difference between analysis and persistence. The SS shows that at 5 and 30 m the forecast is always better than the persistence, but at 300 m it can be worse than persistence for the first days of the forecast. This result may be related to flow adjustments introduced by the data assimilation scheme. The monthly variability of SS shows that when the system variability is high, the values of SS are higher, therefore the forecast has higher skill than persistence. We give evidence that the error growth in the surface layers is controlled by the atmospheric forcing inaccuracies, while at depth the forecast error can be interpreted as due to the data insertion procedure. The data, both in situ and satellite, are not homogeneously distributed in the basin; therefore, the quality of the analyses may be different in different areas of the basin.

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Near-surface ocean current sensors : problems and performance

10.1575/1912/10340 ◽

1979 ◽

Cited By ~ 1

Author(s):

James R. McCullough

Keyword(s):

Ocean Current ◽

Near Surface ◽

Surface Ocean ◽

Current Sensors ◽

And Performance

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Evaluation of HRCLDAS and ERA5 Datasets for Near-Surface Wind over Hainan Island and South China Sea

Atmosphere ◽

10.3390/atmos12060766 ◽

2021 ◽

Vol 12 (6) ◽

pp. 766

Author(s):

Yi Jiang ◽

Shuai Han ◽

Chunxiang Shi ◽

Tao Gao ◽

Honghui Zhen ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Surface Wind ◽

Hainan Island ◽

The South China Sea ◽

Wind Data ◽

The South ◽

Near Surface ◽

China Sea

Near-surface wind data are particularly important for Hainan Island and the South China Sea, and there is a wide range of wind data sources. A detailed understanding of the reliability of these datasets can help us to carry out related research. In this study, the hourly near-surface wind data from the High-Resolution China Meteorological Administration (CMA) Land Data Assimilation System (HRCLDAS) and the fifth-generation ECMWF atmospheric reanalysis data (ERA5) were evaluated by comparison with the ground automatic meteorological observation data for Hainan Island and the South China Sea. The results are as follows: (1) the HRCLDAS and ERA5 near-surface wind data trend was basically the same as the observation data trend, but there was a smaller bias, smaller root-mean-square errors, and higher correlation coefficients between the near-surface wind data from HRCLDAS and the observations; (2) the quality of HRCLDAS and ERA5 near-surface wind data was better over the islands of the South China Sea than over Hainan Island land. However, over the coastal areas of Hainan Island and island stations near Sansha, the quality of the HRCLDAS near-surface wind data was better than that of ERA5; (3) the quality of HRCLDAS near-surface wind data was better than that of ERA5 over different types of landforms. The deviation of ERA5 and HRCLDAS wind speed was the largest along the coast, and the quality of the ERA5 wind direction data was poorest over the mountains, whereas that of HRCLDAS was poorest over hilly areas; (4) the accuracy of HRCLDAS at all wind levels was higher than that of ERA5. ERA5 significantly overestimated low-grade winds and underestimated high-grade winds. The accuracy of HRCLDAS wind ratings over the islands of the South China Sea was significantly higher than that over Hainan Island land, especially for the higher wind ratings; and (5) in the typhoon process, the simulation of wind by HRCLDAS was closer to the observations, and its simulation of higher wind speeds was more accurate than the ERA5 simulations.

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Physics-Based Relationship for Pore Pressure and Vertical Stress Monitoring Using Seismic Velocity Variations

Remote Sensing ◽

10.3390/rs13142684 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2684

Author(s):

Eldert Fokker ◽

Elmer Ruigrok ◽

Rhys Hawkins ◽

Jeannot Trampert

Keyword(s):

Pore Pressure ◽

Seismic Velocity ◽

Pressure Head ◽

Groundwater Table ◽

Surface Velocity ◽

Seismic Velocities ◽

Stress Monitoring ◽

Near Surface ◽

Velocity Variations ◽

Velocity Changes

Previous studies examining the relationship between the groundwater table and seismic velocities have been guided by empirical relationships only. Here, we develop a physics-based model relating fluctuations in groundwater table and pore pressure with seismic velocity variations through changes in effective stress. This model justifies the use of seismic velocity variations for monitoring of the pore pressure. Using a subset of the Groningen seismic network, near-surface velocity changes are estimated over a four-year period, using passive image interferometry. The same velocity changes are predicted by applying the newly derived theory to pressure-head recordings. It is demonstrated that the theory provides a close match of the observed seismic velocity changes.

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Intra-Annual Variability of the Radiocarbon Content of Corals from the Galapagos Islands

Radiocarbon ◽

10.1017/s0033822200064912 ◽

1993 ◽

Vol 35 (2) ◽

pp. 245-251 ◽

Cited By ~ 25

Author(s):

T. A. Brown ◽

G. W. Farwell ◽

P. M. Grootes ◽

F. H. Schmidt ◽

Minze Stuiver

Keyword(s):

Southern Oscillation ◽

Galapagos Islands ◽

Ocean Current ◽

Galápagos Islands ◽

Ocean Water ◽

Annual Variations ◽

Surface Ocean ◽

Annual Variability ◽

Annual Changes ◽

Detailed Record

We report AMS 14C measurements on subannual samples of coral from the Galapagos Islands that span the period, 1970–1973. Both the major 1972 El Niño/Southern Oscillation event and intra-annual changes in regional upwelling of 14C-depleted waters associated with alternation of surface-ocean current patterns are evident in the record. Our data show that the corals preserve a detailed record of past intra-annual variations of the 14C content of surface ocean water.

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