Downloads & Free Reading Options - Results

This DRI TECHNICAL PROGRAM (Emerging Dynamics Of The Marginal Ice Zone) brings together a high-level (global) scientific team in order to better understand the ocean, sea ice and atmosphere interaction within the marginal ice zone (MIZ) north of Alaska. The aim of this multi-disciplinary group is to deliver a step change in our understanding of the processes within the MIZ. This is being achieved through a comprehensive, and continuous observational program of the key physical parameters that influence the development of the MIZ. Our long-term goal is to determine the complex inter-linkages between atmosphere-ice-ocean processes so that, ultimately, parameterisations of MIZ processes can be developed for large-scale models. Our team s role in this DRI is to better understand the ice-ocean-interactions within the MIZ. This is being achieved through the deployment (2014) an autonomous data acquisition network of ice mass balance buoys (IMBs), wave buoys (WBs), and Automatic Weather Stations (AWS) in the region north of Alaska.

We study a simplified coupled atmosphere-ocean model using the formalism of covariant Lyapunov vectors (CLVs), which link physically-based directions of perturbations to growth/decay rates. The model is obtained via a severe truncation of quasi-geostrophic equations for the two fluids, and includes a simple yet physically meaningful representation of their dynamical/thermodynamical coupling. The model has 36 degrees of freedom, and the parameters are chosen so that a chaotic behaviour is observed. One finds two positive Lyapunov exponents (LEs), sixteen negative LEs, and eighteen near-zero LEs. The presence of many near-zero LEs results from the vast time-scale separation between the characteristic time scales of the two fluids, and leads to nontrivial error growth properties in the tangent space spanned by the corresponding CLVs, which are geometrically very degenerate. Such CLVs correspond to two different classes of ocean/atmosphere coupled modes. The tangent space spanned by the CLVs corresponding to the positive and negative LEs has, instead, a non-pathological behaviour, and one can construct robust large deviations laws for the finite time LEs, thus providing a universal model for assessing predictability on long to ultra-long scales along such directions. It is somewhat surprising to find that the tangent space of the unstable manifold has strong projection on both atmospheric and oceanic components. Our results underline the difficulties in using hyperbolicity as a conceptual framework for multiscale chaotic dynamical systems, whereas the framework of partial hyperbolicity seems better suited, possibly indicating an alternative definition for the chaotic hypothesis. Our results suggest the need for accurate analysis of error dynamics on different time scales and domains and for a careful set-up of assimilation schemes when looking at coupled atmosphere-ocean models.

x, 298 p. : 25 cm

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO's), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO's to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of ocean-atmosphere feedbacks. The objectives and immediate scientific goals of the proposed research are: 1. Develop and test the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model for MJO predictability and feedback process studies; 2. Develop and test a WRF-ROMS regional coupled model for MJO predictability and feedback process studies; 3. Test the NCAR CCSM coupled model for MJO predictability and in feedback process studies.

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO's), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO's to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of ocean-atmosphere feedbacks. The objectives and immediate scientific goals of the proposed research are: 1. Develop and test the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model for MJO predictability and feedback process studies; 2. Develop and test a WRF-ROMS regional coupled model for MJO predictability and feedback process studies; 3. Test the NCAR CCSM coupled model for MJO predictability and in feedback process studies.

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO's), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO's to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of oceanatmosphere feedbacks. The objectives and immediate scientific goals of the proposed research are: 1. Develop and test the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model for MJO predictability and feedback process studies; 2. Develop and test a WRF-ROMS regional coupled model for MJO predictability and feedback process studie; 3. Test the NCAR CCSM coupled model for MJO predictability and in feedback process studies.

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO s), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO s to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of ocean-atmosphere feedbacks. The objectives and immediate scientific goals of the proposed research are: 1. Develop and test the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model for MJO predictability and feedback process studies; 2. Develop and test a WRF-ROMS regional coupled model (SCOAR2) for MJO predictability and feedback process studies; 3. Test the NCAR CCSM coupled model for MJO predictability and in feedback process studies.

A numerical model of the circulation of a coupled axisymmetric atmosphere-ocean system was constructed to investigate the physical factors governing the location and intensity of the Intertropical Convergence Zone (ITCZ) over oceans and over land. The results of several numerical integrations are presented to illustrate the interaction of the individual atmospheric and oceanic circulations. It is shown that the ITCA cannot be located at the equator because the atmosphere-ocean system is unstable for lateral displacements of the ITCA from an equilibrium position at the equator.

A systematic, unifying approach to the dynamics of the ocean and atmosphere is given in this book, with emphasis on the larger-scale motions (from a few kilometers to global scale). The foundations of the subject (the equations of state and dynamical equations) are covered in some detail, so that students with training in mathematics should find it a self-contained text. Knowledge of fluid mechanics is helpful but not essential. Simple mathematical models are used to demonstrate the fundamental dynamical principles with plentiful illustrations from field and laboratory.

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO s), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO s to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of ocean-atmosphere feedbacks. The objectives and immediate scientific goals of the proposed research are: 1. Develop and test the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model for MJO predictability and feedback process studies; 2. Develop and test a WRF-ROMS regional coupled model (SCOAR2) for MJO predictability and feedback process studies; 3. Test the NCAR CCSM coupled model for MJO predictability and in feedback process studies.

A brief investigation is presented of long-term variability of the tropical heat supply of the Pacific Ocean and its influence on the atmospheric circulation. From the record of monthly sea and air temperature at Canton Island, 2 deg 48 min S, 171 deg 43 min W, November 1964 is selected as typifying the arid conditions associated with anomalously cold equatorial water, and as representing a contrast to November 1965 with its near-maximum water temperature and abundant rainfall. Air circulation also differs significantly here. The large-scale effect on the atmosphere from November 1964 to November 1965 is described as a general warming of the complete belt of the tropical troposphere with inherent strengthening of the upper tropospheric westerlies in both hemispheres.

A brief investigation is presented of long-term variability of the tropical heat supply of the Pacific Ocean and its influence on the atmospheric circulation. From the record of monthly sea and air temperature at Canton Island, 2 deg 48 min S, 171 deg 43 min W, November 1964 is selected as typifying the arid conditions associated with anomalously cold equatorial water, and as representing a contrast to November 1965 with its near-maximum water temperature and abundant rainfall. Air circulation also differs significantly here. The large-scale effect on the atmosphere from November 1964 to November 1965 is described as a general warming of the complete belt of the tropical troposphere with inherent strengthening of the upper tropospheric westerlies in both hemispheres.

A system of five ordinary differential equations is studied which combines the Lorenz-84 model for the atmosphere and a box model for the ocean. The behaviour of this system is studied as a function of the coupling parameters. For most parameter values, the dynamics of the atmosphere model is dominant. For a range of parameter values, competing attractors exist. The Kaplan-Yorke dimension and the correlation dimension of the chaotic attractor are numerically calculated and compared to the values found in the uncoupled Lorenz model. In the transition from periodic behaviour to chaos intermittency is observed. The intermittent behaviour occurs near a Neimark-Sacker bifurcation at which a periodic solution loses its stability. The length of the periodic intervals is governed by the time scale of the ocean component. Thus, in this regime the ocean model has a considerable influence on the dynamics of the coupled system.

A system of five ordinary differential equations is studied which combines the Lorenz-84 model for the atmosphere and a box model for the ocean. The behaviour of this system is studied as a function of the coupling parameters. For most parameter values, the dynamics of the atmosphere model is dominant. For a range of parameter values, competing attractors exist. The Kaplan-Yorke dimension and the correlation dimension of the chaotic attractor are numerically calculated and compared to the values found in the uncoupled Lorenz model. In the transition from periodic behaviour to chaos intermittency is observed. The intermittent behaviour occurs near a Neimark-Sacker bifurcation at which a periodic solution loses its stability. The length of the periodic intervals is governed by the time scale of the ocean component. Thus, in this regime the ocean model has a considerable influence on the dynamics of the coupled system.

This paper is concerned with the long-time behavior of solutions for the three dimensional primitive equations of large-scale ocean and atmosphere dynamics in an unbounded domain. Since the Sobolev embedding is no longer compact in an unbounded domain, we cannot obtain the asymptotical compactness of the semigroup generated by problem (2.4)-(2.6) by the Sobolev compactness embedding theorem even if we obtain the existence of an absorbing set in more regular phase space. To overcome this difficulty, we first prove the asymptotical compactness in a weak phase space of the semigroup generated by problem (2.4)-(2.6) by combining the tail-estimates and the energy methods. Thanks to the existence of an absorbing set in more regular phase space, we establish the existence of a global attractor of problem (2.4)-(2.6) by virtue of Sobolev interpolation inequality.

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO s), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO s to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of ocean-atmosphere feedbacks. The objectives and immediate scientific goals of the proposed research are: 1. Develop and test the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model for MJO predictability and feedback process studies; 2. Develop and test a WRF-ROMS regional coupled model (SCOAR2) for MJO predictability and feedback process studies; 3. Test the NCAR CCSM coupled model for MJO predictability and in feedback process studies.

The investigation of the coupled atmosphere-ocean system is not only scientifically challenging but also practically important. We consider a coupled atmosphere-ocean model, which involves hydrodynamics, thermodynamics, and random atmospheric dynamics due to short time influences at the air-sea interface. We reformulate this model as a random dynamical system. First, we have shown that the asymptotic dynamics of the coupled atmosphere-ocean model is described by a random climatic attractor. Second, we have estimated the atmospheric temperature evolution under oceanic feedback, in terms of the freshwater flux, heat flux and the external fluctuation at the air-sea interface, as well as the earth's longwave radiation coefficient and the shortwave solar radiation profile. Third, we have demonstrated that this system has finite degree of freedom by presenting a finite set of determining functionals in probability. Finally, we have proved that the coupled atmosphere-ocean model is ergodic under suitable conditions for physical parameters and randomness, and thus for any observable of the coupled atmosphere-ocean flows, its time average approximates the statistical ensemble average, as long as the time interval is sufficiently long.

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO's), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO's to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of ocean-atmosphere feedbacks. The objectives and immediate scientific goals of the proposed research are: 1. Develop and test the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model for MJO predictability and feedback process studies; 2. Develop and test a WRF-ROMS regional coupled model for MJO predictability and feedback process studies; 3. Test the NCAR CCSM coupled model for MJO predictability and in feedback process studies.

Our long-term goal is to develop a coupled ocean-atmosphere model that has significant and quantified skill in predicting the evolution of Madden-Julian Oscillations (MJO s), which is highly relevant to ONR long-term objectives. This requires developing a better understanding of the sensitivities of the atmospheric circulation associated with MJO s to small-scale SST anomalies, regional-scale SST anomalies, the diurnal cycle, surface waves, upper-ocean mixing, and various other aspects of ocean-atmosphere feedbacks.

We consider a coupled atmosphere-ocean model, which involves hydrodynamics, thermodynamics and nonautonomous interaction at the air-sea interface. First, we show that the coupled atmosphere-ocean system is stable under the external fluctuation in the atmospheric energy balance relation. Then, we estimate the atmospheric temperature feedback in terms of the freshwater flux, heat flux and the external fluctuation at the air-sea interface, as well as the earth's longwave radiation coefficient and the shortwave solar radiation profile. Finally, we prove that the coupled atmosphere-ocean system has time-periodic, quasiperiodic and almost periodic motions, whenever the external fluctuation in the atmospheric energy balance relation is time-periodic, quasiperiodic and almost periodic, respectively.

We consider a coupled atmosphere-ocean model, which involves hydrodynamics, thermodynamics and nonautonomous interaction at the air-sea interface. First, we show that the coupled atmosphere-ocean system is stable under the external fluctuation in the atmospheric energy balance relation. Then, we estimate the atmospheric temperature feedback in terms of the freshwater flux, heat flux and the external fluctuation at the air-sea interface, as well as the earth's longwave radiation coefficient and the shortwave solar radiation profile. Finally, we prove that the coupled atmosphere-ocean system has time-periodic, quasiperiodic and almost periodic motions, whenever the external fluctuation in the atmospheric energy balance relation is time-periodic, quasiperiodic and almost periodic, respectively.