A comparison of surface wind products over the North Pacific Ocean

Rienecker, Michele M.; Atlas, Robert; Schubert, Siegfried D.; Willett, Cynthia S.

doi:10.1029/95jc03015

Cited by 26 publications

(10 citation statements)

References 23 publications

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“…The errors are probably due to the closed western boundary and an overly diffuse thermocline in the eastern basin in the model [ Yuan and Rienecker , 2003] that produces overestimated amplitudes of sea level oscillations in the eastern basin (see later). Errors of the wind stress [ Rienecker et al , 1996] can also produce inaccuracies in the simulated circulation, which may ultimately contribute to the model‐altimetry difference through errors of the simulated TIWs. These errors of TIWs, produced by either wind or model errors, are difficult to estimate in the present experiment, except that the error of the closed western boundary can be estimated explicitly through an integration of the Kelvin wave equation and has been shown in the wind‐forced waves (see later).…”

Section: Seasonal Cycle Simulationmentioning

confidence: 99%

Role of the Kelvin and Rossby waves in the seasonal cycle of the equatorial Pacific Ocean circulation

Yuan¹

2005

J. Geophys. Res.

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[1] The dynamics of the seasonal cycle of the equatorial Pacific Ocean circulation are investigated in a hindcast study generated by the Poseidon quasi-isopycnal general ocean circulation model forced by wind stress from a Special Sensor Microwave Imager product and heat flux from an atmospheric mixed layer model. The simulated annual and semiannual oscillations are validated by the Tropical Atmosphere-Ocean mooring measurements and the altimetry sea levels on the equator, based on which the roles of the equatorial Kelvin and Rossby waves in the seasonal cycle dynamics are investigated. The Kelvin and Rossby waves are extracted from the hindcast in such a way as to treat the model zonal nonlinear momentum terms and wind stress as forcing terms so that the validity of the linear theory on wave propagation and reflection can be examined. It is found that the reflections of the first baroclinic mode waves at the Pacific western and eastern boundaries are in good agreement with the linear theory. In comparison, the reflections of the second and higher baroclinic mode waves are significantly different from the linear theory, suggesting that the reflections are potentially nonlinear. The hindcast has simulated the westward propagation of the dominant annual oscillations of the seasonal sea level in the central basin and the eastward propagation of the dominant semi-annual oscillations of the seasonal sea level in the western and eastern basins successfully. The westward propagation of the annual oscillations is primarily associated with the annual Rossby waves forced by the annual winds in the eastern-to-central equatorial Pacific, the upwelling phase of which forces progressive springtime reversal of the surface zonal currents from the east to the west. However, the internal dynamics of the ocean alter the amplitudes and phases of the springtime reversal significantly. The results of this study have shown that the internal dynamics of the ocean are an important source of the semiannual oscillations in the equatorial Pacific Ocean. The semi-annual harmonics of the Rossby waves are boosted by the internal dynamics and eventually dominate the seasonal cycle in the far western Pacific. The reflections of the Rossby waves at the western boundary produce semi-annual dominant Kelvin waves, which force significant semi-annual oscillations of sea level in the eastern basin.

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Section: Seasonal Cycle Simulationmentioning

confidence: 99%

Role of the Kelvin and Rossby waves in the seasonal cycle of the equatorial Pacific Ocean circulation

Yuan¹

2005

J. Geophys. Res.

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“…Fortunately, several satellites have observed winds over the ocean during the last two decades, such as the Geo-sat altimeter, the National Aeronautics and Space Administration (NASA) Scatterometer (NSCAT), the Quick Scatterometer (QuikSCAT), the Special Sensor Microwave Imager (SSM/I), European Space Agency Remote Sensing Satellites (ERS-1/2), and water vapor or cloud-derived satellite winds. Comparisons between different observed surface winds or between observed winds and model forecasted/analyzed winds have been studied extensively (Halpern et al 1994;Rienecker et al 1996;Boutin and Etcheto 1996;Meissner et al 2001;Mears et al 2001;Yuan 2004), but no comparisons have been made between SSM/I and QuikSCAT. Boutin and Etcheto (1996) found that SSM/I-retrieved wind speeds are underestimated by more than 1 m s Ϫ1 with respect to ship measurements at high latitudes.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Assimilating SSM/I and QuikSCAT Satellite Winds on Hurricane Isidore Simulations

Chen

2007

Monthly Weather Review

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Three observational datasets of Hurricane Isidore (in 2002) were analyzed and compared: the Special Sensor Microwave Imager (SSM/I), the Quick Scatterometer (QuikSCAT) winds, and dropsonde winds. SSM/I and QuikSCAT winds were on average about 1.9 and 0.3 m s Ϫ1 stronger, respectively, than dropsonde winds. With more than 20 000 points of data, SSM/I wind speed was about 2.2 m s Ϫ1 stronger than QuikSCAT. Comparison of the wind direction observed by QuikSCAT with those from the dropsondes showed that the quality of QuikSCAT data is good. The effect of assimilating SSM/I wind speeds and/or QuikSCAT wind vectors for the analysis of Hurricane Isidore was assessed using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) and its three-dimensional variational data assimilation system. For the Hurricane Isidore case study, it was found that the assimilation of either satellite winds strengthened the cyclonic circulation in the analysis. However, the increment of the QuikSCAT wind analysis is more complicated than that from the SSM/I analysis due to the correction of the storm location, a positive result from the assimilation of wind vectors. The increase in low-level wind speeds enhanced the air-sea interaction processes and improved the simulated intensity for Isidore. In addition, the storm structure was better simulated. Assimilation of QuikSCAT wind vectors clearly improved simulation of the storm track, in particular during the later period of the simulation, but lack of information about the wind direction from SSM/I data prevented it from having much of an effect. Assessing the assimilation of QuikSCAT wind speed versus wind vector data confirmed this hypothesis. The track improvement partially resulted from the relocation of the storm's initial position after assimilation of the wind vectors.

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“…The wind speed observations of SSMI have also been processed using the 2d‐VAR for the entire period of operational SSMI data [ Atlas et al , 1991, 1993, 1996]. The resulting wind fields have proven useful in forcing ocean models in several studies [ Busalacchi et al , 1993; Liu et al , 1996; Atlas et al , 1996; Rienecker et al , 1996] and in assessing the impact of satellite information on surface wind stress estimates [ Ponte and Rosen , 1993]. In this study, we examine the use of 2d‐VAR for NSCAT ambiguity removal.…”

Section: Ambiguity Removal Proceduresmentioning

confidence: 99%

A comparison of a two‐dimensional variational analysis method and a median filter for NSCAT ambiguity removal

Henderson¹

2003

J. Geophys. Res.

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[1] The ocean surface vector wind can be measured from space by scatterometers. For a set of measurements observed from several viewing directions and collocated in space and time, there will usually exist two, three, or four consistent wind vectors. These multiple wind solutions are known as ambiguities. Ambiguity removal procedures select one ambiguity at each location. We compare results of two different ambiguity removal algorithms, the operational median filter (MF) used by the Jet Propulsion Laboratory (JPL) and a two-dimensional variational analysis method (2d-VAR). We applied 2d-VAR to the entire NASA Scatterometer (NSCAT) mission, orbit by orbit, using European Centre for Medium-Range Weather Forecasts (ECMWF) 10-m wind analyses as background fields. We also applied 2d-VAR to a 51-day subset of the NSCAT mission using National Centers for Environmental Prediction (NCEP) 1000-hPa wind analyses as background fields. This second data set uses the same background fields as the MF data set. When both methods use the same NCEP background fields as a starting point for ambiguity removal, agreement is very good: Approximately only 3% of the wind vector cells (WVCs) have different ambiguity selections; however, most of the WVCs with changes occur in coherent patches. Since at least one of the selections is in error, this implies that errors due to ambiguity selection are not isolated, but are horizontally correlated. When we examine ambiguity selection differences at synoptic scales, we often find that the 2d-VAR selections are more meteorologically reasonable and more consistent with cloud imagery.

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A comparison of surface wind products over the North Pacific Ocean

Cited by 26 publications

References 23 publications

Role of the Kelvin and Rossby waves in the seasonal cycle of the equatorial Pacific Ocean circulation

Role of the Kelvin and Rossby waves in the seasonal cycle of the equatorial Pacific Ocean circulation

The Impact of Assimilating SSM/I and QuikSCAT Satellite Winds on Hurricane Isidore Simulations

A comparison of a two‐dimensional variational analysis method and a median filter for NSCAT ambiguity removal

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