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• 1. [Article] Production of global sea surface temperature fields for the jet propulsion laboratory workshop comparisons

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Production of global sea surface temperature fields for the jet propulsion laboratory workshop comparisons Author: Chelton, Dudley B., Njoku, Eni G., Hilland, Jeffrey E. Copyrighted by American Geophysical Union. Title: Production of global sea surface temperature fields for the jet propulsion laboratory workshop comparisons Author: Chelton, Dudley B., Njoku, Eni G., Hilland, Jeffrey E. Copyrighted by American Geophysical Union. Close

• 2. [Article] Covariability of Surface Wind and Stress Responses to Sea Surface Temperature Fronts

  This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://www.ametsoc.org/pubs/journals/jcli/.

  Citation × Citation Citation Abstract Copy Title: Covariability of Surface Wind and Stress Responses to Sea Surface Temperature Fronts Author: Chelton, Dudley B., Esbensen, Steven K., O'Neill, Larry W. This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://www.ametsoc.org/pubs/journals/jcli/. Title: Covariability of Surface Wind and Stress Responses to Sea Surface Temperature Fronts Author: Chelton, Dudley B., Esbensen, Steven K., O'Neill, Larry W. This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://www.ametsoc.org/pubs/journals/jcli/. Close

• 3. [Article] Coupling between Sea Surface Temperature and Low-Level Winds in Mesoscale Numerical Models

  This study evaluates the impacts of sea surface temperature (SST) specification and grid resolution on numerical simulations of air–sea coupling near oceanic fronts through analyses of surface winds from ...

  Citation × Citation Citation Abstract Copy Title: Coupling between Sea Surface Temperature and Low-Level Winds in Mesoscale Numerical Models Author: Chelton, Dudley B., Thum, Nicolai, Esbensen, Steven K., O’Neill, Larry W., Song, Qingtao This study evaluates the impacts of sea surface temperature (SST) specification and grid resolution on numerical simulations of air–sea coupling near oceanic fronts through analyses of surface winds from the European Centre for Medium-Range Weather Forecasts (ECMWF) model. The 9 May 2001 change of the boundary condition from the Reynolds SST analyses to the NOAA Real-Time Global (RTG) SST in the ECMWF model resulted in an abrupt increase in mesoscale variance of the model surface winds over the ocean. In contrast, the 21 November 2000 change of the grid resolution resulted in an abrupt increase in mesoscale variability of surface winds over mountainous regions on land but had no significant effect on winds over the ocean. To further investigate model sensitivity to the SST boundary condition and grid resolution, a series of simulations were made with the Weather Research and Forecasting (WRF) model over a domain encompassing the Agulhas return current (ARC: also called “retroflection”) region in the south Indian Ocean. Results from three WRF simulations with SST measured by the Advanced Microwave Scanning Radiometer on the Earth Observing System Aqua satellite (AMSR-E) and the Reynolds and RTG SST analyses indicate the vital importance of the resolution of the SST boundary condition for accurate simulation of the air–sea coupling between SST and surface wind speed. WRF simulations with grid spacings of 40 and 25 km show that the latter increased energy only on scales shorter than 250 km. In contrast, improved resolution of SST significantly increased the mesoscale variability for scales up to 1000 km. Further sensitivity studies with the WRF model conclude that the weak coupling of surface wind speeds from the ECMWF model to SST is likely attributable primarily to the weak response of vertical turbulent mixing to SST-induced stability in the parameterization of boundary layer turbulence, with an overestimation of vertical diffusion by about 60% on average in stable conditions and an underestimation by about 40% in unstable conditions Title: Coupling between Sea Surface Temperature and Low-Level Winds in Mesoscale Numerical Models Author: Chelton, Dudley B., Thum, Nicolai, Esbensen, Steven K., O’Neill, Larry W., Song, Qingtao This study evaluates the impacts of sea surface temperature (SST) specification and grid resolution on numerical simulations of air–sea coupling near oceanic fronts through analyses of surface winds from the European Centre for Medium-Range Weather Forecasts (ECMWF) model. The 9 May 2001 change of the boundary condition from the Reynolds SST analyses to the NOAA Real-Time Global (RTG) SST in the ECMWF model resulted in an abrupt increase in mesoscale variance of the model surface winds over the ocean. In contrast, the 21 November 2000 change of the grid resolution resulted in an abrupt increase in mesoscale variability of surface winds over mountainous regions on land but had no significant effect on winds over the ocean. To further investigate model sensitivity to the SST boundary condition and grid resolution, a series of simulations were made with the Weather Research and Forecasting (WRF) model over a domain encompassing the Agulhas return current (ARC: also called “retroflection”) region in the south Indian Ocean. Results from three WRF simulations with SST measured by the Advanced Microwave Scanning Radiometer on the Earth Observing System Aqua satellite (AMSR-E) and the Reynolds and RTG SST analyses indicate the vital importance of the resolution of the SST boundary condition for accurate simulation of the air–sea coupling between SST and surface wind speed. WRF simulations with grid spacings of 40 and 25 km show that the latter increased energy only on scales shorter than 250 km. In contrast, improved resolution of SST significantly increased the mesoscale variability for scales up to 1000 km. Further sensitivity studies with the WRF model conclude that the weak coupling of surface wind speeds from the ECMWF model to SST is likely attributable primarily to the weak response of vertical turbulent mixing to SST-induced stability in the parameterization of boundary layer turbulence, with an overestimation of vertical diffusion by about 60% on average in stable conditions and an underestimation by about 40% in unstable conditions Close

• 4. [Article] Subseasonal SST Variability in the Tropical Eastern North Pacific during Boreal Summer

  Boreal summer intraseasonal (30–90-day time scale) sea surface temperature (SST) variability in the east Pacific warm pool is examined using Tropical Rainfall Measuring Mission (TRMM) Microwave Imager ...

  Citation × Citation Citation Abstract Copy Title: Subseasonal SST Variability in the Tropical Eastern North Pacific during Boreal Summer Author: Chelton, Dudley B., Esbensen, Steven K., Maloney, Eric D. Boreal summer intraseasonal (30–90-day time scale) sea surface temperature (SST) variability in the east Pacific warm pool is examined using Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) sea surface temperatures during 1998–2005. Intraseasonal SST variance maximizes at two locations in the warm pool: in the vicinity of 9°N, 92°W near the Costa Rica Dome and near the northern edge of the warm pool in the vicinity of 19°N, 108°W. Both locations exhibit a significant spectral peak at 50–60-day periods, time scales characteristic of the Madden–Julian oscillation (MJO). Complex empirical orthogonal function (CEOF) and spectra coherence analyses are used to show that boreal summer intraseasonal SST anomalies are coherent with precipitation anomalies across the east Pacific warm pool. Spatial variations of phase are modest across the warm pool, although evidence exists for the northward progression of intraseasonal SST and precipitation anomalies. Intraseasonal SSTs at the north edge of the warm pool lag those in the vicinity of the Costa Rica Dome by about 1 week. The MJO explains 30%–40% of the variance of intraseasonal SST anomalies in the east Pacific warm pool during boreal summer. Peak-to-peak SST variations of 0.8°–1.0°C occur during MJO events. SST is approximately in quadrature with MJO precipitation, with suppressed (enhanced) MJO precipitation anomalies leading positive (negative) SST anomalies by 7–10 days. Consistent with the CEOF and coherence analyses, MJO-related SST and precipitation anomalies near the Costa Rica Dome lead those at the northern edge of the warm pool by about 1 week. Title: Subseasonal SST Variability in the Tropical Eastern North Pacific during Boreal Summer Author: Chelton, Dudley B., Esbensen, Steven K., Maloney, Eric D. Boreal summer intraseasonal (30–90-day time scale) sea surface temperature (SST) variability in the east Pacific warm pool is examined using Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) sea surface temperatures during 1998–2005. Intraseasonal SST variance maximizes at two locations in the warm pool: in the vicinity of 9°N, 92°W near the Costa Rica Dome and near the northern edge of the warm pool in the vicinity of 19°N, 108°W. Both locations exhibit a significant spectral peak at 50–60-day periods, time scales characteristic of the Madden–Julian oscillation (MJO). Complex empirical orthogonal function (CEOF) and spectra coherence analyses are used to show that boreal summer intraseasonal SST anomalies are coherent with precipitation anomalies across the east Pacific warm pool. Spatial variations of phase are modest across the warm pool, although evidence exists for the northward progression of intraseasonal SST and precipitation anomalies. Intraseasonal SSTs at the north edge of the warm pool lag those in the vicinity of the Costa Rica Dome by about 1 week. The MJO explains 30%–40% of the variance of intraseasonal SST anomalies in the east Pacific warm pool during boreal summer. Peak-to-peak SST variations of 0.8°–1.0°C occur during MJO events. SST is approximately in quadrature with MJO precipitation, with suppressed (enhanced) MJO precipitation anomalies leading positive (negative) SST anomalies by 7–10 days. Consistent with the CEOF and coherence analyses, MJO-related SST and precipitation anomalies near the Costa Rica Dome lead those at the northern edge of the warm pool by about 1 week. Close

• 5. [Article] Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature Perturbations

  This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/mwre.

  Citation × Citation Citation Abstract Copy Title: Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature Perturbations Author: Chelton, Dudley B., Skyllingstad, Eric D., Samelson, Roger M., de Szoeke, Simon P., O'Neill, Larry W., Perlin, Natalie This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/mwre. Title: Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature Perturbations Author: Chelton, Dudley B., Skyllingstad, Eric D., Samelson, Roger M., de Szoeke, Simon P., O'Neill, Larry W., Perlin, Natalie This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/mwre. Close

• 6. [Article] Global Microwave Satellite Observations of Sea Surface Temperature for Numerical Weather Prediction and Climate Research

  Obtaining global sea surface temperature (SST) fields for the ocean boundary condition in numerical weather prediction (NWP) models and for climate research has long been problematic. Historically, such ...

  Citation × Citation Citation Abstract Copy Title: Global Microwave Satellite Observations of Sea Surface Temperature for Numerical Weather Prediction and Climate Research Author: Chelton, Dudley B., Wentz, Frank J. Obtaining global sea surface temperature (SST) fields for the ocean boundary condition in numerical weather prediction (NWP) models and for climate research has long been problematic. Historically, such fields have been constructed by a blending of in situ observations from ships and buoys and satellite infrared observations from the Advanced Very High Resolution Radiometer (AVHRR) that has been operational on NOAA satellites since November 1981. The resolution of these global SST fields is limited by the sparse coverage of in situ observations in many areas of the World Ocean and cloud contamination of AVHRR observations, which can exceed 75% over the subpolar oceans. As clouds and aerosols are essentially transparent to microwave radiation, satellite microwave observations can greatly improve the sampling and resolution of global SST fields. The Advanced Microwave Scanning Radiometer on the NASA Earth Observing System (EOS) Aqua satellite (AMSR-E) is providing the first highly accurate and global satellite microwave observations of SST. The potential for AMSR-E observations to improve the sampling, resolution, and accuracy of SST fields for NWP and climate research is demonstrated from example SST fields and from an investigation of the sensitivity of NWP models to specification of the SST boundary condition. Title: Global Microwave Satellite Observations of Sea Surface Temperature for Numerical Weather Prediction and Climate Research Author: Chelton, Dudley B., Wentz, Frank J. Obtaining global sea surface temperature (SST) fields for the ocean boundary condition in numerical weather prediction (NWP) models and for climate research has long been problematic. Historically, such fields have been constructed by a blending of in situ observations from ships and buoys and satellite infrared observations from the Advanced Very High Resolution Radiometer (AVHRR) that has been operational on NOAA satellites since November 1981. The resolution of these global SST fields is limited by the sparse coverage of in situ observations in many areas of the World Ocean and cloud contamination of AVHRR observations, which can exceed 75% over the subpolar oceans. As clouds and aerosols are essentially transparent to microwave radiation, satellite microwave observations can greatly improve the sampling and resolution of global SST fields. The Advanced Microwave Scanning Radiometer on the NASA Earth Observing System (EOS) Aqua satellite (AMSR-E) is providing the first highly accurate and global satellite microwave observations of SST. The potential for AMSR-E observations to improve the sampling, resolution, and accuracy of SST fields for NWP and climate research is demonstrated from example SST fields and from an investigation of the sensitivity of NWP models to specification of the SST boundary condition. Close

• 7. [Article] Central California Coastal Circulation Study : CTD observations, cruise 8401, February 1984

  Citation × Citation Citation Abstract Copy Title: Central California Coastal Circulation Study : CTD observations, cruise 8401, February 1984 Author: Chelton, Dudley B., Oregon State University. College of Oceanography, Kosro, P. Michael, 1951- Title: Central California Coastal Circulation Study : CTD observations, cruise 8401, February 1984 Author: Chelton, Dudley B., Oregon State University. College of Oceanography, Kosro, P. Michael, 1951- Close

• 8. [Article] Central California Coastal Circulation Study : CTD observations , cruise 8403, July 1984

  Citation × Citation Citation Abstract Copy Title: Central California Coastal Circulation Study : CTD observations , cruise 8403, July 1984 Author: Kosro, P. Michael, 1951-, Oregon State University. College of Oceanography, Chelton, Dudley B. Title: Central California Coastal Circulation Study : CTD observations , cruise 8403, July 1984 Author: Kosro, P. Michael, 1951-, Oregon State University. College of Oceanography, Chelton, Dudley B. Close

• 9. [Article] Central California Coastal Circulation Study : CTD observations, cruise 8404, October 1984

  Citation × Citation Citation Abstract Copy Title: Central California Coastal Circulation Study : CTD observations, cruise 8404, October 1984 Author: Kosro, P. Michael, 1951-, Oregon State University. College of Oceanography, Chelton, Dudley B. Title: Central California Coastal Circulation Study : CTD observations, cruise 8404, October 1984 Author: Kosro, P. Michael, 1951-, Oregon State University. College of Oceanography, Chelton, Dudley B. Close

• 10. [Article] Central California Coastal Circulation Study : CTD observations, cruise 8501, January 1985

  Citation × Citation Citation Abstract Copy Title: Central California Coastal Circulation Study : CTD observations, cruise 8501, January 1985 Author: Chelton, Dudley B., Oregon State University. College of Oceanography, Kosro, P. Michael, 1951- Title: Central California Coastal Circulation Study : CTD observations, cruise 8501, January 1985 Author: Chelton, Dudley B., Oregon State University. College of Oceanography, Kosro, P. Michael, 1951- Close

• 11. [Article] Air–Sea Heat Exchange along the Northern Sea Surface Temperature Front in the Eastern Tropical Pacific

  The atmospheric response to the oceanic forcing in the eastern Pacific along the northern equatorial sea surface temperature (SST) front is investigated in terms of sensible and latent heat flux during ...

  Citation × Citation Citation Abstract Copy Title: Air–Sea Heat Exchange along the Northern Sea Surface Temperature Front in the Eastern Tropical Pacific Author: Chelton, Dudley B., McPhaden, Michael J., Thum, Nicolai, Esbensen, Steven K. The atmospheric response to the oceanic forcing in the eastern Pacific along the northern equatorial sea surface temperature (SST) front is investigated in terms of sensible and latent heat flux during the 6-month period from 28 July 1999 to 27 January 2000 and the 7-month period from 28 June 2000 to 27 January 2001. Of particular interest is the atmospheric boundary layer (ABL) response to oceanic tropical instability waves (TIWs) that distort the SST front during May–January in normal years. In previous studies, time series of surface heat fluxes clearly show the influence of TIWs, but the relationship to spatial patterns of SST and wind speed has been inferred only from sparse in situ data. In this study, satellite observations are used as a basis for compositing in situ data from moorings to compensate for the lack of a spatially dense mooring array. The variability in the position of the SST front caused by westward-propagating TIWs enables fixed mooring locations to measure the ABL response from a large range of locations relative to the front. The satellite data enable determination of the precise location of the mooring relative to the front. The advantage of this strategy is the recurring measurement of the ABL response to the SST front over the 13-month period considered here. The results indicate that the TIW-induced perturbations of sensible heat flux are spatially shifted in phase toward the east relative to the perturbations of SST. The maximum fluxes of sensible heat are not centered directly over the warmest water, but are shifted toward the portion of the frontal region where a disequilibrium boundary layer is expected due to the advection of colder air from the equatorial region. The latent heat flux pattern is approximately in phase with the SST, with only a slight shift to the east. The changes of sensible and latent heat fluxes across the SST front have typical magnitudes of about 12 and 125 W m⁻², respectively. The sensible and latent heat flux patterns are interpreted in two complementary ways: 1) as an atmospheric response to the change of oceanic forcing as air flows across the SST front, and 2) as the atmospheric response to westward-propagating TIWs along the SST front. Title: Air–Sea Heat Exchange along the Northern Sea Surface Temperature Front in the Eastern Tropical Pacific Author: Chelton, Dudley B., McPhaden, Michael J., Thum, Nicolai, Esbensen, Steven K. The atmospheric response to the oceanic forcing in the eastern Pacific along the northern equatorial sea surface temperature (SST) front is investigated in terms of sensible and latent heat flux during the 6-month period from 28 July 1999 to 27 January 2000 and the 7-month period from 28 June 2000 to 27 January 2001. Of particular interest is the atmospheric boundary layer (ABL) response to oceanic tropical instability waves (TIWs) that distort the SST front during May–January in normal years. In previous studies, time series of surface heat fluxes clearly show the influence of TIWs, but the relationship to spatial patterns of SST and wind speed has been inferred only from sparse in situ data. In this study, satellite observations are used as a basis for compositing in situ data from moorings to compensate for the lack of a spatially dense mooring array. The variability in the position of the SST front caused by westward-propagating TIWs enables fixed mooring locations to measure the ABL response from a large range of locations relative to the front. The satellite data enable determination of the precise location of the mooring relative to the front. The advantage of this strategy is the recurring measurement of the ABL response to the SST front over the 13-month period considered here. The results indicate that the TIW-induced perturbations of sensible heat flux are spatially shifted in phase toward the east relative to the perturbations of SST. The maximum fluxes of sensible heat are not centered directly over the warmest water, but are shifted toward the portion of the frontal region where a disequilibrium boundary layer is expected due to the advection of colder air from the equatorial region. The latent heat flux pattern is approximately in phase with the SST, with only a slight shift to the east. The changes of sensible and latent heat fluxes across the SST front have typical magnitudes of about 12 and 125 W m⁻², respectively. The sensible and latent heat flux patterns are interpreted in two complementary ways: 1) as an atmospheric response to the change of oceanic forcing as air flows across the SST front, and 2) as the atmospheric response to westward-propagating TIWs along the SST front. Close

• 12. [Article] Frontal Scale Air–Sea Interaction in High-Resolution Coupled Climate Models

  The emerging picture of frontal scale air–sea interaction derived from high-resolution satellite observations of surface winds and sea surface temperature (SST) provides a unique opportunity to test the ...

  Citation × Citation Citation Abstract Copy Title: Frontal Scale Air–Sea Interaction in High-Resolution Coupled Climate Models Author: Chelton, Dudley B., McClean, Julie L., Loeb, Norman G., Dennis, John M., Bryan, Frank O., Tomas, Robert The emerging picture of frontal scale air–sea interaction derived from high-resolution satellite observations of surface winds and sea surface temperature (SST) provides a unique opportunity to test the fidelity of high-resolution coupled climate simulations. Initial analysis of the output of a suite of Community Climate System Model (CCSM) experiments indicates that characteristics of frontal scale ocean–atmosphere interaction, such as the positive correlation between SST and surface wind stress, are realistically captured only when the ocean component is eddy resolving. The strength of the coupling between SST and surface stress is weaker than observed, however, as has been found previously for numerical weather prediction models and other coupled climate models. The results are similar when the atmospheric component model grid resolution is doubled from 0.5° to 0.25°, an indication that shortcomings in the representation of subgrid scale atmospheric planetary boundary layer processes, rather than resolved scale processes, are responsible for the weakness of the coupling. In the coupled model solutions the response to mesoscale SST features is strongest in the atmospheric boundary layer, but there is a deeper reaching response of the atmospheric circulation apparent in free tropospheric clouds. This simulated response is shown to be consistent with satellite estimates of the relationship between mesoscale SST and all-sky albedo. Title: Frontal Scale Air–Sea Interaction in High-Resolution Coupled Climate Models Author: Chelton, Dudley B., McClean, Julie L., Loeb, Norman G., Dennis, John M., Bryan, Frank O., Tomas, Robert The emerging picture of frontal scale air–sea interaction derived from high-resolution satellite observations of surface winds and sea surface temperature (SST) provides a unique opportunity to test the fidelity of high-resolution coupled climate simulations. Initial analysis of the output of a suite of Community Climate System Model (CCSM) experiments indicates that characteristics of frontal scale ocean–atmosphere interaction, such as the positive correlation between SST and surface wind stress, are realistically captured only when the ocean component is eddy resolving. The strength of the coupling between SST and surface stress is weaker than observed, however, as has been found previously for numerical weather prediction models and other coupled climate models. The results are similar when the atmospheric component model grid resolution is doubled from 0.5° to 0.25°, an indication that shortcomings in the representation of subgrid scale atmospheric planetary boundary layer processes, rather than resolved scale processes, are responsible for the weakness of the coupling. In the coupled model solutions the response to mesoscale SST features is strongest in the atmospheric boundary layer, but there is a deeper reaching response of the atmospheric circulation apparent in free tropospheric clouds. This simulated response is shown to be consistent with satellite estimates of the relationship between mesoscale SST and all-sky albedo. Close

• 13. [Article] Observations of Coupling between Surface Wind Stress and Sea Surface Temperature in the Eastern Tropical Pacific

  Satellite measurements of surface wind stress from the QuikSCAT scatterometer and sea surface temperature (SST) from the Tropical Rainfall Measuring Mission Microwave Imager are analyzed for the three-month ...

  Citation × Citation Citation Abstract Copy Title: Observations of Coupling between Surface Wind Stress and Sea Surface Temperature in the Eastern Tropical Pacific Author: Chelton, Dudley B., McPhaden, Michael J., Schlax, Michael G., Freilich, Michael H., Thum, Nicolai, Esbensen, Steven K., Gentemann, Chelle L., Wentz, Frank J., Schopf, Paul S. Satellite measurements of surface wind stress from the QuikSCAT scatterometer and sea surface temperature (SST) from the Tropical Rainfall Measuring Mission Microwave Imager are analyzed for the three-month period 21 July–20 October 1999 to investigate ocean–atmosphere coupling in the eastern tropical Pacific. Oceanic tropical instability waves (TIWs) with periods of 20–40 days and wavelengths of 1000–2000 km perturb the SST fronts that bracket both sides of the equatorial cold tongue, which is centered near 1°S to the east of 130°W. These perturbations are characterized by cusp-shaped features that propagate systematically westward on both sides of the equator. The space–time structures of these SST perturbations are reproduced with remarkable detail in the surface wind stress field. The wind stress divergence is shown to be linearly related to the downwind component of the SST gradient with a response on the south side of the cold tongue that is about twice that on the north side. The wind stress curl is linearly related to the crosswind component of the SST gradient with a response that is approximately half that of the wind stress divergence response to the downwind SST gradient. The perturbed SST and wind stress fields propagate synchronously westward with the TIWs. This close coupling between SST and wind stress supports the Wallace et al. hypothesis that surface winds vary in response to SST modification of atmospheric boundary layer stability. Title: Observations of Coupling between Surface Wind Stress and Sea Surface Temperature in the Eastern Tropical Pacific Author: Chelton, Dudley B., McPhaden, Michael J., Schlax, Michael G., Freilich, Michael H., Thum, Nicolai, Esbensen, Steven K., Gentemann, Chelle L., Wentz, Frank J., Schopf, Paul S. Satellite measurements of surface wind stress from the QuikSCAT scatterometer and sea surface temperature (SST) from the Tropical Rainfall Measuring Mission Microwave Imager are analyzed for the three-month period 21 July–20 October 1999 to investigate ocean–atmosphere coupling in the eastern tropical Pacific. Oceanic tropical instability waves (TIWs) with periods of 20–40 days and wavelengths of 1000–2000 km perturb the SST fronts that bracket both sides of the equatorial cold tongue, which is centered near 1°S to the east of 130°W. These perturbations are characterized by cusp-shaped features that propagate systematically westward on both sides of the equator. The space–time structures of these SST perturbations are reproduced with remarkable detail in the surface wind stress field. The wind stress divergence is shown to be linearly related to the downwind component of the SST gradient with a response on the south side of the cold tongue that is about twice that on the north side. The wind stress curl is linearly related to the crosswind component of the SST gradient with a response that is approximately half that of the wind stress divergence response to the downwind SST gradient. The perturbed SST and wind stress fields propagate synchronously westward with the TIWs. This close coupling between SST and wind stress supports the Wallace et al. hypothesis that surface winds vary in response to SST modification of atmospheric boundary layer stability. Close

• 14. [Article] The Effects of SST-Induced Surface Wind Speed and Direction Gradients on Midlatitude Surface Vorticity and Divergence

  The effects of surface wind speed and direction gradients on midlatitude surface vorticity and divergence fields associated with mesoscale sea surface temperature (SST) variability having spatial scales ...

  Citation × Citation Citation Abstract Copy Title: The Effects of SST-Induced Surface Wind Speed and Direction Gradients on Midlatitude Surface Vorticity and Divergence Author: Chelton, Dudley B., Esbensen, Steven K., O’Neill, Larry W. The effects of surface wind speed and direction gradients on midlatitude surface vorticity and divergence fields associated with mesoscale sea surface temperature (SST) variability having spatial scales of 100–1000 km are investigated using vector wind observations from the SeaWinds scatterometer on the Quick Scatterometer (QuikSCAT) satellite and SST from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) Aqua satellite. The wind–SST coupling is analyzed over the period June 2002–August 2008, corresponding to the first 6+ years of the AMSR-E mission. Previous studies have shown that strong wind speed gradients develop in response to persistent mesoscale SST features associated with the Kuroshio Extension, Gulf Stream, South Atlantic, and Agulhas Return Current regions. Midlatitude SST fronts also significantly modify surface wind direction; the surface wind speed and direction responses to typical SST differences of about 2°–4°C are, on average, about 1–2 m s⁻¹ and 4°–8°, respectively, over all four regions. Wind speed perturbations are positively correlated and very nearly collocated spatially with the SST perturbations. Wind direction perturbations, however, are displaced meridionally from the SST perturbations, with cyclonic flow poleward of warm SST and anticyclonic flow poleward of cool SST. Previous observational analyses have shown that small-scale perturbations in the surface vorticity and divergence fields are related linearly to the crosswind and downwind components of the SST gradient, respectively. When the vorticity and divergence fields are analyzed in curvilinear natural coordinates, the wind speed contributions to the SST-induced vorticity and divergence depend equally on the crosswind and downwind SST gradients, respectively. SST-induced wind direction gradients also significantly modify the vorticity and divergence fields, weakening the vorticity response to crosswind SST gradients while enhancing the divergence response to downwind SST gradients. Title: The Effects of SST-Induced Surface Wind Speed and Direction Gradients on Midlatitude Surface Vorticity and Divergence Author: Chelton, Dudley B., Esbensen, Steven K., O’Neill, Larry W. The effects of surface wind speed and direction gradients on midlatitude surface vorticity and divergence fields associated with mesoscale sea surface temperature (SST) variability having spatial scales of 100–1000 km are investigated using vector wind observations from the SeaWinds scatterometer on the Quick Scatterometer (QuikSCAT) satellite and SST from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) Aqua satellite. The wind–SST coupling is analyzed over the period June 2002–August 2008, corresponding to the first 6+ years of the AMSR-E mission. Previous studies have shown that strong wind speed gradients develop in response to persistent mesoscale SST features associated with the Kuroshio Extension, Gulf Stream, South Atlantic, and Agulhas Return Current regions. Midlatitude SST fronts also significantly modify surface wind direction; the surface wind speed and direction responses to typical SST differences of about 2°–4°C are, on average, about 1–2 m s⁻¹ and 4°–8°, respectively, over all four regions. Wind speed perturbations are positively correlated and very nearly collocated spatially with the SST perturbations. Wind direction perturbations, however, are displaced meridionally from the SST perturbations, with cyclonic flow poleward of warm SST and anticyclonic flow poleward of cool SST. Previous observational analyses have shown that small-scale perturbations in the surface vorticity and divergence fields are related linearly to the crosswind and downwind components of the SST gradient, respectively. When the vorticity and divergence fields are analyzed in curvilinear natural coordinates, the wind speed contributions to the SST-induced vorticity and divergence depend equally on the crosswind and downwind SST gradients, respectively. SST-induced wind direction gradients also significantly modify the vorticity and divergence fields, weakening the vorticity response to crosswind SST gradients while enhancing the divergence response to downwind SST gradients. Close

• 15. [Article] Comparisons of Daily Sea Surface Temperature Analyses for 2007–08

  Six different SST analyses are compared with each other and with buoy data for the period 2007–08. All analyses used different combinations of satellite data [for example, infrared Advanced Very High Resolution ...

  Citation × Citation Citation Abstract Copy Title: Comparisons of Daily Sea Surface Temperature Analyses for 2007–08 Author: Chelton, Dudley B., Reynolds, Richard W. Six different SST analyses are compared with each other and with buoy data for the period 2007–08. All analyses used different combinations of satellite data [for example, infrared Advanced Very High Resolution Radiometer (AVHRR) and microwave Advanced Microwave Scanning Radiometer (AMSR) instruments] with different algorithms, spatial resolution, etc. The analyses considered are the National Climatic Data Center (NCDC) AVHRR-only and AMSR+AVHRR, the Navy Coupled Ocean Data Assimilation (NCODA), the Remote Sensing Systems (RSS), the Real-Time Global High-Resolution (RTG-HR), and the Operational SST and Sea Ice Analysis (OSTIA); the spatial grid sizes were 1/4°, 1/4°, 1/9°, 1/11°, 1/12°, and 1/20°, respectively. In addition, all analyses except RSS used in situ data. Most analysis procedures and weighting functions differed. Thus, differences among analyses could be large in high-gradient and data-sparse regions. An example off the coast of South Carolina showed winter SST differences that exceeded 5°C. To help quantify SST analysis differences, wavenumber spectra were computed at several locations. These results suggested that the RSS is much noisier and that the RTG-HR analysis is much smoother than the other analyses. Further comparisons made using collocated buoys showed that RSS was especially noisy in the tropics and that RTG-HR had winter biases near the Aleutians region during January and February 2007. The correlation results show that NCODA and, to a somewhat lesser extent, OSTIA are strongly tuned locally to buoy data. The results also show that grid spacing does not always correlate with analysis resolution. The AVHRR-only analysis is useful for climate studies because it is the only daily SST analysis that extends back to September 1981. Furthermore, comparisons of the AVHRR-only analysis and the AMSR+AVHRR analysis show that AMSR data can degrade the combined AMSR and AVHRR resolution in cloud-free regions while AMSR otherwise improves the resolution. These results indicate that changes in satellite instruments over time can impact SST analysis resolution. Title: Comparisons of Daily Sea Surface Temperature Analyses for 2007–08 Author: Chelton, Dudley B., Reynolds, Richard W. Six different SST analyses are compared with each other and with buoy data for the period 2007–08. All analyses used different combinations of satellite data [for example, infrared Advanced Very High Resolution Radiometer (AVHRR) and microwave Advanced Microwave Scanning Radiometer (AMSR) instruments] with different algorithms, spatial resolution, etc. The analyses considered are the National Climatic Data Center (NCDC) AVHRR-only and AMSR+AVHRR, the Navy Coupled Ocean Data Assimilation (NCODA), the Remote Sensing Systems (RSS), the Real-Time Global High-Resolution (RTG-HR), and the Operational SST and Sea Ice Analysis (OSTIA); the spatial grid sizes were 1/4°, 1/4°, 1/9°, 1/11°, 1/12°, and 1/20°, respectively. In addition, all analyses except RSS used in situ data. Most analysis procedures and weighting functions differed. Thus, differences among analyses could be large in high-gradient and data-sparse regions. An example off the coast of South Carolina showed winter SST differences that exceeded 5°C. To help quantify SST analysis differences, wavenumber spectra were computed at several locations. These results suggested that the RSS is much noisier and that the RTG-HR analysis is much smoother than the other analyses. Further comparisons made using collocated buoys showed that RSS was especially noisy in the tropics and that RTG-HR had winter biases near the Aleutians region during January and February 2007. The correlation results show that NCODA and, to a somewhat lesser extent, OSTIA are strongly tuned locally to buoy data. The results also show that grid spacing does not always correlate with analysis resolution. The AVHRR-only analysis is useful for climate studies because it is the only daily SST analysis that extends back to September 1981. Furthermore, comparisons of the AVHRR-only analysis and the AMSR+AVHRR analysis show that AMSR data can degrade the combined AMSR and AVHRR resolution in cloud-free regions while AMSR otherwise improves the resolution. These results indicate that changes in satellite instruments over time can impact SST analysis resolution. Close

• 16. [Article] Summertime Coupling between Sea Surface Temperature and Wind Stress in the California Current System

  Satellite observations of wind stress and sea surface temperature (SST) are analyzed to investigate ocean–atmosphere interaction in the California Current System (CCS). As in regions of strong SST fronts ...

  Citation × Citation Citation Abstract Copy Title: Summertime Coupling between Sea Surface Temperature and Wind Stress in the California Current System Author: Chelton, Dudley B., Schlax, Michael G., Samelson, Roger M. Satellite observations of wind stress and sea surface temperature (SST) are analyzed to investigate ocean–atmosphere interaction in the California Current System (CCS). As in regions of strong SST fronts elsewhere in the World Ocean, SST in the CCS region is positively correlated with surface wind stress when SST fronts are strong, which occurs during the summertime in the CCS region. This ocean influence on the atmosphere is apparently due to SST modification of stability and mixing in the atmospheric boundary layer and is most clearly manifest in the derivative wind stress fields: wind stress curl and divergence are linearly related to, respectively, the crosswind and downwind components of the local SST gradient. The dynamic range of the Ekman upwelling velocities associated with the summertime SST-induced perturbations of the wind stress curl is larger than that of the upwelling velocities associated with the mean summertime wind stress curl. This suggests significant feedback effects on the ocean, which likely modify the SST distribution that perturbed the wind stress curl field. The atmosphere and ocean off the west coast of North America must therefore be considered a fully coupled system. It is shown that the observed summertime ocean–atmosphere interaction is poorly represented in the NOAA North American Mesoscale Model (formerly called the Eta Model). This is due, at least in part, to the poor resolution and accuracy of the SST boundary condition used in the model. The sparse distribution of meteorological observations available over the CCS for data assimilation may also contribute to the poor model performance. Title: Summertime Coupling between Sea Surface Temperature and Wind Stress in the California Current System Author: Chelton, Dudley B., Schlax, Michael G., Samelson, Roger M. Satellite observations of wind stress and sea surface temperature (SST) are analyzed to investigate ocean–atmosphere interaction in the California Current System (CCS). As in regions of strong SST fronts elsewhere in the World Ocean, SST in the CCS region is positively correlated with surface wind stress when SST fronts are strong, which occurs during the summertime in the CCS region. This ocean influence on the atmosphere is apparently due to SST modification of stability and mixing in the atmospheric boundary layer and is most clearly manifest in the derivative wind stress fields: wind stress curl and divergence are linearly related to, respectively, the crosswind and downwind components of the local SST gradient. The dynamic range of the Ekman upwelling velocities associated with the summertime SST-induced perturbations of the wind stress curl is larger than that of the upwelling velocities associated with the mean summertime wind stress curl. This suggests significant feedback effects on the ocean, which likely modify the SST distribution that perturbed the wind stress curl field. The atmosphere and ocean off the west coast of North America must therefore be considered a fully coupled system. It is shown that the observed summertime ocean–atmosphere interaction is poorly represented in the NOAA North American Mesoscale Model (formerly called the Eta Model). This is due, at least in part, to the poor resolution and accuracy of the SST boundary condition used in the model. The sparse distribution of meteorological observations available over the CCS for data assimilation may also contribute to the poor model performance. Close

• 17. [Article] Objective Determination of Feature Resolution in Two Sea Surface Temperature Analyses

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American ...

  Citation × Citation Citation Abstract Copy Title: Objective Determination of Feature Resolution in Two Sea Surface Temperature Analyses Author: Roberts-Jones, Jonah, Martin, Matthew J., Menemenlis, Dimitris, Merchant, Christopher John, Chelton, Dudley B., Reynolds, Richard W. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://www.ametsoc.org/pubs/journals/jcli/. Title: Objective Determination of Feature Resolution in Two Sea Surface Temperature Analyses Author: Roberts-Jones, Jonah, Martin, Matthew J., Menemenlis, Dimitris, Merchant, Christopher John, Chelton, Dudley B., Reynolds, Richard W. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://www.ametsoc.org/pubs/journals/jcli/. Close

• 18. [Article] Satellite Microwave SST Observations of Transequatorial Tropical Instability Waves

  Satellite measurements of sea-surface temperature (SST) by the TRMM Microwave Imager reveal previously unreported features of tropical instability waves (TIWs). In the Pacific, TIW-related variability ...

  Citation × Citation Citation Abstract Copy Title: Satellite Microwave SST Observations of Transequatorial Tropical Instability Waves Author: Chelton, Dudley B., Schlax, Michael G., Genremann, Chelle L., Wentz, Frank J., de Szoeke, Roland A. Satellite measurements of sea-surface temperature (SST) by the TRMM Microwave Imager reveal previously unreported features of tropical instability waves (TIWs). In the Pacific, TIW-related variability is observed from the eastern boundary to at least 160°E. Cusp-shaped distortions of SST fronts and associated trains of anticyclonic vortices both north and south of the equator propagate westward at ~0.5 m s-1 with approximately 50% larger meridional displacements in the north. In the Atlantic, TIWs and associated anticyclonic vortices are clearly observed only on the north side of the equator where they propagate from the eastern boundary to the western boundary at ~0.3 m s-1. Title: Satellite Microwave SST Observations of Transequatorial Tropical Instability Waves Author: Chelton, Dudley B., Schlax, Michael G., Genremann, Chelle L., Wentz, Frank J., de Szoeke, Roland A. Satellite measurements of sea-surface temperature (SST) by the TRMM Microwave Imager reveal previously unreported features of tropical instability waves (TIWs). In the Pacific, TIW-related variability is observed from the eastern boundary to at least 160°E. Cusp-shaped distortions of SST fronts and associated trains of anticyclonic vortices both north and south of the equator propagate westward at ~0.5 m s-1 with approximately 50% larger meridional displacements in the north. In the Atlantic, TIWs and associated anticyclonic vortices are clearly observed only on the north side of the equator where they propagate from the eastern boundary to the western boundary at ~0.3 m s-1. Close

• 19. [Article] Geographical Variability of the First Baroclinic Rossby Radius of Deformation

  Global 1° × 1° climatologies of the first baroclinic gravity-wave phase speed c¹ and the Rossby radius of deformation λ1 are computed from climatological average temperature and salinity profiles. These ...

  Citation × Citation Citation Abstract Copy Title: Geographical Variability of the First Baroclinic Rossby Radius of Deformation Author: El Naggar, Karim, Chelton, Dudley B., Schlax, Michael G., Siwertz, Nicolas, deSzoeke, Roland A. Global 1° × 1° climatologies of the first baroclinic gravity-wave phase speed c¹ and the Rossby radius of deformation λ1 are computed from climatological average temperature and salinity profiles. These new atlases are compared with previously published 5° × 5° coarse resolution maps of λ₁ for the Northern Hemisphere and the South Atlantic and with a 1° × 1° fine-resolution map of c₁ for the tropical Pacific. It is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5%–15% owing to seemingly minor computational errors. Geographical variations in the new high-resolution maps of c₁ and λ₁ are discussed in terms of a WKB approximation that elucidates the effects of earth rotation, stratification, and water depth on these quantities. It is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c₁ and λ₁ at any particular location in the World Ocean. This is rationalized from consideration of the WKB approximation. Title: Geographical Variability of the First Baroclinic Rossby Radius of Deformation Author: El Naggar, Karim, Chelton, Dudley B., Schlax, Michael G., Siwertz, Nicolas, deSzoeke, Roland A. Global 1° × 1° climatologies of the first baroclinic gravity-wave phase speed c¹ and the Rossby radius of deformation λ1 are computed from climatological average temperature and salinity profiles. These new atlases are compared with previously published 5° × 5° coarse resolution maps of λ₁ for the Northern Hemisphere and the South Atlantic and with a 1° × 1° fine-resolution map of c₁ for the tropical Pacific. It is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5%–15% owing to seemingly minor computational errors. Geographical variations in the new high-resolution maps of c₁ and λ₁ are discussed in terms of a WKB approximation that elucidates the effects of earth rotation, stratification, and water depth on these quantities. It is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c₁ and λ₁ at any particular location in the World Ocean. This is rationalized from consideration of the WKB approximation. Close

• 20. [Article] Dynamical Analysis of the Boundary Layer and Surface Wind Responses to Mesoscale SST Perturbations

  The dynamical response of the marine atmospheric boundary layer (MABL) to mesoscale sea surface temperature (SST) perturbations is investigated over the Agulhas Return Current during winter from a 1-month, ...

  Citation × Citation Citation Abstract Copy Title: Dynamical Analysis of the Boundary Layer and Surface Wind Responses to Mesoscale SST Perturbations Author: Chelton, Dudley B., Thum, Nicolai, Samelson, Roger M., O’Neill, Larry W., Esbensen, Steven K. The dynamical response of the marine atmospheric boundary layer (MABL) to mesoscale sea surface temperature (SST) perturbations is investigated over the Agulhas Return Current during winter from a 1-month, high-resolution, three-dimensional simulation using the Weather Research and Forecasting (WRF) mesoscale model. A steady lower boundary condition for July 2002 is obtained using SST measurements from the Advanced Microwave Scanning Radiometer on the Earth Observing System (EOS)–Aqua satellite (AMSR-E). The WRF models’ ability to accurately simulate the SST-induced surface wind response is demonstrated from a comparison with satellite surface wind observations from the SeaWinds scatterometer on the Quick Scatterometer (QuikSCAT) satellite. Relevant features of this simulation include a quasi-periodic distribution of mesoscale SST perturbations with spatial scales ~200 km and strong winds that lead to a large surface sensible heat flux response, whose broad range of 80–100 W m⁻² between warm and cool SST perturbations is much larger than seen in most previous simulations of mesoscale wind–SST coupling. This simulation provides the first realistic example of vertical turbulent redistribution of momentum driven by the SST-induced surface heating perturbations acting in concert with the SST-induced pressure gradients to accelerate near-surface flow toward warm water and decelerate near-surface flow toward cool water. This simulation is also the first example of a near-surface wind speed response to mesoscale SST perturbations that differs qualitatively and substantially from the vertically averaged MABL wind response. In the vertically averaged MABL momentum budget, the surface wind stress acts as a drag on the SST-induced perturbation flow as it is being accelerated by SST-induced pressure gradients. However, only in the middle and upper reaches of the MABL does the turbulent stress divergence act as a drag on the SST-induced winds perturbations in this simulation. These mesoscale SST perturbations are also shown to modify the wind direction within the MABL. Dynamically, this is accomplished through SST-induced perturbations to the crosswind components of the pressure gradient, turbulent stress divergence, and the Coriolis force. Title: Dynamical Analysis of the Boundary Layer and Surface Wind Responses to Mesoscale SST Perturbations Author: Chelton, Dudley B., Thum, Nicolai, Samelson, Roger M., O’Neill, Larry W., Esbensen, Steven K. The dynamical response of the marine atmospheric boundary layer (MABL) to mesoscale sea surface temperature (SST) perturbations is investigated over the Agulhas Return Current during winter from a 1-month, high-resolution, three-dimensional simulation using the Weather Research and Forecasting (WRF) mesoscale model. A steady lower boundary condition for July 2002 is obtained using SST measurements from the Advanced Microwave Scanning Radiometer on the Earth Observing System (EOS)–Aqua satellite (AMSR-E). The WRF models’ ability to accurately simulate the SST-induced surface wind response is demonstrated from a comparison with satellite surface wind observations from the SeaWinds scatterometer on the Quick Scatterometer (QuikSCAT) satellite. Relevant features of this simulation include a quasi-periodic distribution of mesoscale SST perturbations with spatial scales ~200 km and strong winds that lead to a large surface sensible heat flux response, whose broad range of 80–100 W m⁻² between warm and cool SST perturbations is much larger than seen in most previous simulations of mesoscale wind–SST coupling. This simulation provides the first realistic example of vertical turbulent redistribution of momentum driven by the SST-induced surface heating perturbations acting in concert with the SST-induced pressure gradients to accelerate near-surface flow toward warm water and decelerate near-surface flow toward cool water. This simulation is also the first example of a near-surface wind speed response to mesoscale SST perturbations that differs qualitatively and substantially from the vertically averaged MABL wind response. In the vertically averaged MABL momentum budget, the surface wind stress acts as a drag on the SST-induced perturbation flow as it is being accelerated by SST-induced pressure gradients. However, only in the middle and upper reaches of the MABL does the turbulent stress divergence act as a drag on the SST-induced winds perturbations in this simulation. These mesoscale SST perturbations are also shown to modify the wind direction within the MABL. Dynamically, this is accomplished through SST-induced perturbations to the crosswind components of the pressure gradient, turbulent stress divergence, and the Coriolis force. Close