Download or read book Investigating Marine Boundary Layer Parameterizations by Combining Observations with Models Via State Estimation written by and published by . This book was released on 2015 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this project we have improved numerical weather prediction analyses and forecasts of low level winds in the marine boundary layer. This has been accomplished with the following tools; The National Center for Atmospheric Research (NCAR) Weather and Research Forecasting model, WRF, both in his single column (SCM) and three-dimensional (3D) versions; The National Oceanic and Atmospheric Administration (NOAA) Wave Watch III (WWIII); SE algorithms from the Data Assimilation Research Testbed (DART, Anderson et al. 2009); and Observations of key quantities of the lower MBL, including temperature and winds at multiple levels above the sea surface. The experiments with the WRF SCM / DART system have lead to large improvements with respect to a standard WRF configuration, which is currently commonly used by the wind energy industry. The single column model appears to be a tool particularly suitable for off-shore wind energy applications given its accuracy, the ability to quantify uncertainty, and the minimal computational resource requirements. In situations where the impact of an upwind wind park may be of interest in a downwind location, a 3D approach may be more suitable. We have demonstrated that with the WRF 3D / DART system the accuracy of wind predictions (and other meteorological parameters) can be improved over a 3D computational domain, and not only at specific locations. All the scripting systems developed in this project (i.e., to run WRF SCM / DART, WRF 3D / DART, and the coupling between WRF and WWIII) and the several modifications and upgrades made to the WRF SCM model will be shared with the broader community.
Download or read book Boundary Layer Dynamics written by National Research Council and published by National Academies Press. This book was released on 1997-04-24 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ocean Modeling and Parameterization written by Eric P. Chassignet and published by Springer Science & Business Media. This book was released on 1998-08-31 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: The realism of large scale numerical ocean models has improved dra matically in recent years, in part because modern computers permit a more faithful representation of the differential equations by their algebraic analogs. Equally significant, if not more so, has been the improved under standing of physical processes on space and time scales smaller than those that can be represented in such models. Today, some of the most challeng ing issues remaining in ocean modeling are associated with parameterizing the effects of these high-frequency, small-space scale processes. Accurate parameterizations are especially needed in long term integrations of coarse resolution ocean models that are designed to understand the ocean vari ability within the climate system on seasonal to decadal time scales. Traditionally, parameterizations of subgrid-scale, high-frequency mo tions in ocean modeling have been based on simple formulations, such as the Reynolds decomposition with constant diffusivity values. Until recently, modelers were concerned with first order issues such as a correct represen tation of the basic features of the ocean circulation. As the numerical simu lations become better and less dependent on the discretization choices, the focus is turning to the physics of the needed parameterizations and their numerical implementation. At the present time, the success of any large scale numerical simulation is directly dependent upon the choices that are made for the parameterization of various subgrid processes.
Download or read book Marine Boundary Layer Parameterizations for Large Scale Models written by L. Mahrt and published by . This book was released on 1994 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes work on the PL atmospheric boundary-layer model conducted under contract number F19628-91-K-0002 from the Phillips Laboratory. This model was developed to provide turbulence parameterization schemes for a global numerical weather prediction model. In this report, boundary-layer nonlocal turbulent mixing is reexamined, and a nonlocal momentum mixing formulation is presented. The boundary-layer cloud formulation, that accounts for turbulent and subgrid-mesoscale moisture variations, is extended to include enhanced cloud mixing using moist conservative variables. Observational data and results from model simulations are used to examine the complex land-surface/atmosphere interactions and the potential for cloud development. Exchange coefficients for subgrid fluxes are shown to depend significantly on grid size in the presence mesoscale motion induced by surface heterogeneity. Tower and aircraft-measured fluxes over heterogeneous terrain are analyzed to show the spatial variation of surface fluxes and the effect on the surface exchange coefficients for area-averaged fluxes. The classical bulk aerodynamic method for estimating surface fluxes in terms of surface radiative temperature is examined. A new sea-surface roughness formulation includes the effects of aerodynamically smooth and rough flow, and wave age in terms of a simple wind tendency relation. Subgrid variability, Atmospheric boundary-layer, Surface fluxes, Boundary-layer model, Surface energy balance, Cloud cover parameterization, Ocean surface roughness.
Download or read book Marine Boundary Layer Parameterizations for Large Scale Models Data Analysis and Verification written by and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The data sampling and analysis techniques associated with research under this AASERT grant will aid in better estimates of fluxes from observations, a requirement for model verification. The new analysis techniques allow decomposition of the flow into localized modes which are more natural to boundary layer problems compared to the usual Fourier decomposition. The analysis techniques are applicable to observational data sets as well as numerical output. The usual assumption of alignment of the surface stress and surface wind vector was reexamined. This assumption appears to break down with significant temperature advection. This problem was examined in terms of tower data collected in the coastal zone by the Risoe National Laboratory (Denmark). The usual formulation of the surface heat flux in models is inconsistent in that the aerodynamic temperature required for Monin-Okukhov similarity theory is replaced by the surface radiation temperature. The aerodynamic temperature is not readily available and numerous empirical fixes have been suggested to dose the system. The approach here documents these problems by relating the evaporative fraction to remotely sensed information using data from the Boreal Ecosystem-Atmosphere Study and the California Ozone Deposition Experiment.
Download or read book Parameterization Schemes written by David J. Stensrud and published by Cambridge University Press. This book was released on 2007-05-03 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents: 1.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oceanobs 19 An Ocean of Opportunity Volume II written by Tong Lee and published by Frontiers Media SA. This book was released on 2020-12-31 with total page 629 pages. Available in PDF, EPUB and Kindle. Book excerpt: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.
Download or read book Uncertainty Quantification in Ocean State Estimation written by Alexander G. Kalmikov and published by . This book was released on 2013 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantifying uncertainty and error bounds is a key outstanding challenge in ocean state estimation and climate research. It is particularly difficult due to the large dimensionality of this nonlinear estimation problem and the number of uncertain variables involved. The "Estimating the Circulation and Climate of the Oceans" (ECCO) consortium has developed a scalable system for dynamically consistent estimation of global time-evolving ocean state by optimal combination of ocean general circulation model (GCM) with diverse ocean observations. The estimation system is based on the "adjoint method" solution of an unconstrained least-squares optimization problem formulated with the method of Lagrange multipliers for fitting the dynamical ocean model to observations. The dynamical consistency requirement of ocean state estimation necessitates this approach over sequential data assimilation and reanalysis smoothing techniques. In addition, it is computationally advantageous because calculation and storage of large covariance matrices is not required. However, this is also a drawback of the adjoint method, which lacks a native formalism for error propagation and quantification of assimilated uncertainty. The objective of this dissertation is to resolve that limitation by developing a feasible computational methodology for uncertainty analysis in dynamically consistent state estimation, applicable to the large dimensionality of global ocean models. Hessian (second derivative-based) methodology is developed for Uncertainty Quantification (UQ) in large-scale ocean state estimation, extending the gradient-based adjoint method to employ the second order geometry information of the model-data misfit function in a high-dimensional control space. Large error covariance matrices are evaluated by inverting the Hessian matrix with the developed scalable matrix-free numerical linear algebra algorithms. Hessian-vector product and Jacobian derivative codes of the MIT general circulation model (MITgcm) are generated by means of algorithmic differentiation (AD). Computational complexity of the Hessian code is reduced by tangent linear differentiation of the adjoint code, which preserves the speedup of adjoint checkpointing schemes in the second derivative calculation. A Lanczos algorithm is applied for extracting the leading rank eigenvectors and eigenvalues of the Hessian matrix. The eigenvectors represent the constrained uncertainty patterns. The inverse eigenvalues are the corresponding uncertainties. The dimensionality of UQ calculations is reduced by eliminating the uncertainty null-space unconstrained by the supplied observations. Inverse and forward uncertainty propagation schemes are designed for assimilating observation and control variable uncertainties, and for projecting these uncertainties onto oceanographic target quantities. Two versions of these schemes are developed: one evaluates reduction of prior uncertainties, while another does not require prior assumptions. The analysis of uncertainty propagation in the ocean model is time-resolving. It captures the dynamics of uncertainty evolution and reveals transient and stationary uncertainty regimes. The system is applied to quantifying uncertainties of Antarctic Circumpolar Current (ACC) transport in a global barotropic configuration of the MITgcm. The model is constrained by synthetic observations of sea surface height and velocities. The control space consists of two-dimensional maps of initial and boundary conditions and model parameters. The size of the Hessian matrix is 0(1010) elements, which would require 0(60GB) of uncompressed storage. It is demonstrated how the choice of observations and their geographic coverage determines the reduction in uncertainties of the estimated transport. The system also yields information on how well the control fields are constrained by the observations. The effects of controls uncertainty reduction due to decrease of diagonal covariance terms are compared to dynamical coupling of controls through off-diagonal covariance terms. The correlations of controls introduced by observation uncertainty assimilation are found to dominate the reduction of uncertainty of transport. An idealized analytical model of ACC guides a detailed time-resolving understanding of uncertainty dynamics. Keywords: Adjoint model uncertainty, sensitivity, posterior error reduction, reduced rank Hessian matrix, Automatic Differentiation, ocean state estimation, barotropic model, Drake Passage transport.
Download or read book Advances in Ocean Data Assimilation Methodologies Forecasting and Reanalysis written by Shiqiu Peng and published by Frontiers Media SA. This book was released on 2023-12-01 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surface Layer Forced Marine Atmospheric Boundary Layer Convective Eddies written by David John Beberwyk and published by . This book was released on 1997-07-01 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boundary layer convective eddies (BLCE) observed via synthetic aperture radar (SAR) on 17 June 1993 during the Hi-Res 2 field experiment are investigated using a three dimensional nonlinear spectral model derived from the shallow Boussinesq equations. Boundary conditions are appropriate for marine atmospheric boundary layer (MABL) flow and allow for heat and momentum fluxes across the lower boundary, as is required to determine sea surface stress patterns. Enhancements made to the model for this study include the addition of an inversion layer, an unstable surface layer and weighted nonlinear numerical dissipation. A more numerically accurate integration scheme is also incorporated. A linear stability analysis of Hi-Res 2 data finds maximum growth rates for disturbances having horizontal wavelengths that match those determined from the 17 June 1993 SAR image. Desirable by products of the analysis include the determination of physically plausible mean horizontal wind profiles and inversion strengths. Two model integrations are performed using identical measured atmospheric input values and initial conditions, but with different dissipation weights.
Download or read book An Investigation of the Wave Boundary Layer and Its Interaction with the Atmospheric Surface Layer written by and published by . This book was released on 1998 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research is to gain a better understanding of the flow characteristics of the marine surface layers, including the coupling at the air-sea interface. Specifically, the research focuses on the influence of ocean waves on turbulent processes, especially those involved in stress-wave interactions. The long range goal of this research is to develop new and/or revise old theoretical descriptions of turbulence, such that they are universally applicable to both over land and over sea boundary layers. This is to be accomplished by focusing on the physical processes unique to the marine boundary layers through a combination of scale analysis and numerical modeling.
Download or read book MTPE EOS Reference Handbook written by and published by . This book was released on 1995 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multi scale fluid physics in oceanic flows New insights from laboratory experiments and numerical simulations written by Shi-Di Huang and published by Frontiers Media SA. This book was released on 2024-01-15 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Weather Review written by and published by . This book was released on 1994 with total page 972 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Marine Fog Challenges and Advancements in Observations Modeling and Forecasting written by Darko Koračin and published by Springer. This book was released on 2017-01-28 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the history of marine fog research and applications, and discusses the physical processes leading to fog's formation, evolution, and dissipation. A special emphasis is on the challenges and advancements of fog observation and modeling as well as on efforts toward operational fog forecasting and linkages and feedbacks between marine fog and the environment.
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 1264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
