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• 1. [Article] Sensible Heat Flux in Near-Neutral Conditions over the Sea

  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/phoc.

  Citation × Citation Citation Abstract Copy Title: Sensible Heat Flux in Near-Neutral Conditions over the Sea Author: Khelif, Djamal, Andreas, Edgar L., Vickers, Dean, Mahrt, L. 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/phoc. Title: Sensible Heat Flux in Near-Neutral Conditions over the Sea Author: Khelif, Djamal, Andreas, Edgar L., Vickers, Dean, Mahrt, L. 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/phoc. Close

• 2. [Article] Turbulent structure in the bora and stable boundary layer

  An eigenvector analysis of the velocity-temperature correlation matrix is applied to clear-air turbulence measured by aircraft in the Bora. The eigenvectors are identified with the main eddies of the turbulence. ...

  Citation × Citation Citation Abstract Copy Title: Turbulent structure in the bora and stable boundary layer Author: Frank, Helmut P. An eigenvector analysis of the velocity-temperature correlation matrix is applied to clear-air turbulence measured by aircraft in the Bora. The eigenvectors are identified with the main eddies of the turbulence. This study attempts to infer the three-dimensional structure of these eddies. The results are compared with turbulent structures in the stable boundary layer. The turbulence in the strongly stratified boundary layer appears to be dominated by double roller eddies with their axes of rotation tilted in the shear direction. The clear-air turbulence shows a larger variety of motion types. Title: Turbulent structure in the bora and stable boundary layer Author: Frank, Helmut P. An eigenvector analysis of the velocity-temperature correlation matrix is applied to clear-air turbulence measured by aircraft in the Bora. The eigenvectors are identified with the main eddies of the turbulence. This study attempts to infer the three-dimensional structure of these eddies. The results are compared with turbulent structures in the stable boundary layer. The turbulence in the strongly stratified boundary layer appears to be dominated by double roller eddies with their axes of rotation tilted in the shear direction. The clear-air turbulence shows a larger variety of motion types. Close

• 3. [Article] Atmospheric boundary layer coupling to midlatitude mesoscale sea surface temperature anomalies

  This thesis examines the mechanisms that couple the monthly-averaged atmospheric boundary layer (ABL) to open-ocean sea surface temperature (SST) perturbations on scales of 50-500 km. The observed positive ...

  Citation × Citation Citation Abstract Copy Title: Atmospheric boundary layer coupling to midlatitude mesoscale sea surface temperature anomalies Author: Thum, Nicolai This thesis examines the mechanisms that couple the monthly-averaged atmospheric boundary layer (ABL) to open-ocean sea surface temperature (SST) perturbations on scales of 50-500 km. The observed positive correlation between surface wind speed anomalies and SST anomalies is successfully simulated using the Weather Research and Forecasting (WRF) model. In numerical experiments with idealized SST fronts, the cross-frontal surface wind acceleration in the cold-to-warm case and deceleration in the warm-to- cold case are found over narrow transition zones co-located with the narrow regions of large frontal SST changes. In the transition zone, horizontal momentum is redistributed vertically in the ABL by turbulence and convection. The largest pressure adjustments, on the other hand, take place over a much broader region downstream from the SST front. In the cold-to-warm transition zone the model simulates an unstable thermal internal boundary layer (TIBL) in the lower part of the ABL. As the TIBL grows, higher velocity air aloft is incorporated into the TIBL, accelerating the flow. Over the warm-to-cold transition zone, the momentum boundary layer collapses, and vertical mixing of momentum by turbulence and convection ceases in the upper part of the ABL. The WRF model is also applied to open-ocean ABL flow across idealized sinusoidal SST anomalies having scales similar to those observed in the Agulhas return current region. The simulated horizontal pressure gradient force anomalies are crucial to the response over the entire domain, and the vertically integrated momentum budget is found to be approximately linear. A linear diagnostic model is therefore developed which successfully predicts the observed phase and amplitude of the ABL wind, pressure and temperature response to the SST anomalies, with largest quantitative discrepancies found in the perturbation wind component perpendicular to the mean wind direction. By using the divergence and vorticity budgets, the diagnostic model shows that differences in the vertical structure of the perturbation wind components down and across the mean wind can explain the differences in the coupling coefficients for the divergence and curl as functions of downwind and crosswind SST gradients, and as functions of the angle between the SST gradient and the mean wind. Title: Atmospheric boundary layer coupling to midlatitude mesoscale sea surface temperature anomalies Author: Thum, Nicolai This thesis examines the mechanisms that couple the monthly-averaged atmospheric boundary layer (ABL) to open-ocean sea surface temperature (SST) perturbations on scales of 50-500 km. The observed positive correlation between surface wind speed anomalies and SST anomalies is successfully simulated using the Weather Research and Forecasting (WRF) model. In numerical experiments with idealized SST fronts, the cross-frontal surface wind acceleration in the cold-to-warm case and deceleration in the warm-to- cold case are found over narrow transition zones co-located with the narrow regions of large frontal SST changes. In the transition zone, horizontal momentum is redistributed vertically in the ABL by turbulence and convection. The largest pressure adjustments, on the other hand, take place over a much broader region downstream from the SST front. In the cold-to-warm transition zone the model simulates an unstable thermal internal boundary layer (TIBL) in the lower part of the ABL. As the TIBL grows, higher velocity air aloft is incorporated into the TIBL, accelerating the flow. Over the warm-to-cold transition zone, the momentum boundary layer collapses, and vertical mixing of momentum by turbulence and convection ceases in the upper part of the ABL. The WRF model is also applied to open-ocean ABL flow across idealized sinusoidal SST anomalies having scales similar to those observed in the Agulhas return current region. The simulated horizontal pressure gradient force anomalies are crucial to the response over the entire domain, and the vertically integrated momentum budget is found to be approximately linear. A linear diagnostic model is therefore developed which successfully predicts the observed phase and amplitude of the ABL wind, pressure and temperature response to the SST anomalies, with largest quantitative discrepancies found in the perturbation wind component perpendicular to the mean wind direction. By using the divergence and vorticity budgets, the diagnostic model shows that differences in the vertical structure of the perturbation wind components down and across the mean wind can explain the differences in the coupling coefficients for the divergence and curl as functions of downwind and crosswind SST gradients, and as functions of the angle between the SST gradient and the mean wind. Close

• 4. [Article] Estimation of momentum, heat and mass transfer in laminar boundary layers

  Sisson's formally exact series solution for momentum, heat and mass transfer in steady two-dimensional or axi-symmetrical constant-property, laminar boundary layer flow was examined. A new series was proposed ...

  Citation × Citation Citation Abstract Copy Title: Estimation of momentum, heat and mass transfer in laminar boundary layers Author: Myers, Gary Allen Sisson's formally exact series solution for momentum, heat and mass transfer in steady two-dimensional or axi-symmetrical constant-property, laminar boundary layer flow was examined. A new series was proposed for the boundary condition accounting for the mass transfer at the surface of the body on which the boundary layer is formed. This series circumvents certain anomalies experienced by the original method and improves the accuracy of the solutions for those flows with suction occurring at the wall. The perturbation theory upon which the original method was based was examined. It was found that the treatment followed in the original work was the better of the two alternatives available. The theory was developed to extend Sisson's formally exact series solution method to flows with a non-constant wall temperature. This new theory yields a more general heat and mass transfer similar flow equation, which contains a temperature parameter that is of the same form as the β parameter in the general momentum similar equation. This general heat and mass transfer similar flow equation was solved for a wide range of the new parameter, the 1 parameter and the mass flux parameter K. An approximation was introduced for simplifying practical calculations. Calculations using this extended method agreed well with the exact solutions with which they were compared. In addition, many flows not considered by Sisson were shown to be accurately solved with the original method. The method of Sisson was found to agree with exact theory for limits of large suction and limits of small Prandtl or Schmidt numbers with little or no mass transfer at the wall. The exact limit of large Prandtl or Schmidt numbers with little or no mass transfer at the surface was approached very closely by the Sisson similar method. A rapid, general, approximate method for the calculation of an average Nusselt number was investigated. It was found to be quite accurate for a wide range of flow conditions. Title: Estimation of momentum, heat and mass transfer in laminar boundary layers Author: Myers, Gary Allen Sisson's formally exact series solution for momentum, heat and mass transfer in steady two-dimensional or axi-symmetrical constant-property, laminar boundary layer flow was examined. A new series was proposed for the boundary condition accounting for the mass transfer at the surface of the body on which the boundary layer is formed. This series circumvents certain anomalies experienced by the original method and improves the accuracy of the solutions for those flows with suction occurring at the wall. The perturbation theory upon which the original method was based was examined. It was found that the treatment followed in the original work was the better of the two alternatives available. The theory was developed to extend Sisson's formally exact series solution method to flows with a non-constant wall temperature. This new theory yields a more general heat and mass transfer similar flow equation, which contains a temperature parameter that is of the same form as the β parameter in the general momentum similar equation. This general heat and mass transfer similar flow equation was solved for a wide range of the new parameter, the 1 parameter and the mass flux parameter K. An approximation was introduced for simplifying practical calculations. Calculations using this extended method agreed well with the exact solutions with which they were compared. In addition, many flows not considered by Sisson were shown to be accurately solved with the original method. The method of Sisson was found to agree with exact theory for limits of large suction and limits of small Prandtl or Schmidt numbers with little or no mass transfer at the wall. The exact limit of large Prandtl or Schmidt numbers with little or no mass transfer at the surface was approached very closely by the Sisson similar method. A rapid, general, approximate method for the calculation of an average Nusselt number was investigated. It was found to be quite accurate for a wide range of flow conditions. Close

• 5. [Article] Wind and Temperature Oscillations Generated by Wave–Turbulence Interactions in the Stably Stratified Boundary Layer

  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/atsc.

  Citation × Citation Citation Abstract Copy Title: Wind and Temperature Oscillations Generated by Wave–Turbulence Interactions in the Stably Stratified Boundary Layer Author: Lenschow, Donald H., Sun, Jielun, Mahrt, Larry, Nappo, Carmen 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/atsc. Title: Wind and Temperature Oscillations Generated by Wave–Turbulence Interactions in the Stably Stratified Boundary Layer Author: Lenschow, Donald H., Sun, Jielun, Mahrt, Larry, Nappo, Carmen 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/atsc. Close

• 6. [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

• 7. [Article] Ship-Based Observations of the Diurnal Cycle of Southeast Pacific Marine Stratocumulus Clouds and Precipitation

  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: Ship-Based Observations of the Diurnal Cycle of Southeast Pacific Marine Stratocumulus Clouds and Precipitation Author: Brewer, W. Alan, Yuter, Sandra E., Burleyson, Casey D., de Szoeke, Simon P., Wilbanks, Matt 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://journals.ametsoc.org/loi/atsc. Title: Ship-Based Observations of the Diurnal Cycle of Southeast Pacific Marine Stratocumulus Clouds and Precipitation Author: Brewer, W. Alan, Yuter, Sandra E., Burleyson, Casey D., de Szoeke, Simon P., Wilbanks, Matt 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://journals.ametsoc.org/loi/atsc. Close

• 8. [Article] Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean

  This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/.

  Citation × Citation Citation Abstract Copy Title: Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean Author: Zuidema, P., Saide, P., Lytle, M., Twohy, C. H., George, R. C., Wood, R., Andrejczuk, M., Spak, S., Leon, D., Anderson, J. R., Adams, A., Toohey, D. W. This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/. Title: Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean Author: Zuidema, P., Saide, P., Lytle, M., Twohy, C. H., George, R. C., Wood, R., Andrejczuk, M., Spak, S., Leon, D., Anderson, J. R., Adams, A., Toohey, D. W. This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/. Close