Table of contents

This review covers recent advances in applying data assimilation techniques to problems in physical oceanography. The introduction and appendices provide the non-specialist reader with background in ocean circulation and observing methods.

The 4D variational assimilation approach is covered in depth showing how model - data misfits can be minimized using Lagrange multipliers in an unconstrained variational problem. Applications to modelling tropical Pacific temperatures, sea surface heights and circulation in the North Atlantic, and tomographic (sound travel time) data are all presented. The use of variational methods for deriving average climatological circulation patterns is also described as well as applications to error growth during numerical forecasting.

The paper then focuses on three important topics in physical oceanography, the evolution of ocean mesoscale eddies in middle latitudes, the development of El Nino events in the tropical Pacific, and the evolution of ocean surface waves. Recent improvements in data acquisition and modelling in these areas mean that data assimilation is practical and is providing new insights and forecasting capabilities to varying degrees. Results using a variety of assimilation techniques are presented, concluding with a forward look to a time when routine forecasting of ocean developments will be possible with important implications ranging from understanding climate change to fishing and pollution control.

The experimental technique of angle- and spin-resolved ultraviolet photoemission has been developed into an important tool for investigating the electronic structure of crystalline materials. Together with the high level in experimental set-up tremendous progress has been achieved in the theoretical description of the photoemission process from solid surfaces. Due to the intensive combination of experimental and theoretical investigations, which has existed for more than 15 years in this area of physical interest, the understanding of the electronic properties of clean and adsorbate-covered surfaces and thin films has grown enormously. This paper reviews the theoretical developments in the field of ultraviolet photoemission. Starting with a brief overview about many-body description of photoemission theory, one-electron models will be introduced with special emphasis on applications. In particular, theoretical aspects like temperature-dependent effects due to phonon excitations, relativistic effects and the influence of strong electron correlations will be discussed, and their importance for quantitative photoemission calculations will be shown by several examples. Furthermore, the review inhibits the modern technique of full-potential photoemission, which allows a more detailed understanding of complex systems like covalently bonded materials, multilayers and adsorbate-covered surfaces. Finally, the wide range of dichroic effects visible in photoemission experiments will be elucidated in the framework of relativistic photoemission theory.