The CP 2 Analytical Plotter

This paper examines the rationale behind the design and development of the CP 2 analytical plotter and shows how the final product, in terms of both hardware and software, has been influenced by the needs of a commercial air survey company.     

Reply to comments by G. Kosarev, N. Petersen and L. P. Vinnik on 'The use of velocity spectrum for stacking receiver functions and imaging upper mantle discontinuities

We thank the editors of GJI for the opportunity to respond to the comment in this issue by Kosarev, Petersen & Vinnik 11996: hereafter referred to as KPV), which disputes the historical and technical accuracy of the paper by Gurrola, Minster & Owens (1994; henceforth referred to as GMO).     

The fog front of 25 May 1989 — A gravity flow?

Summary During the field experiment FRONTEX 1989 a shallow cold front with a fog field behind its leading edge was observed over the North Sea. The fog field was about 70 km wide, 160 m deep at the front side and 400 m deep at the rear side and was capped by a strong frontal inversion. With increasing height of the inversion the fog broke up into cumulus clouds. The horizontal temperature gradient was largest at 500 m with 9 K/100 km. The observed segment of the front was situated near the col of a geostrophic deformation field with vanishing cross-front wind but non-vanishing cross-front confluence. The front moved at a rate of 5 m/s. It exhibits characteristics of a gravity current which propagates into a stably stratified environment.The physical processes leading to the observed frontal structure and motion are elucidated by experiments with a two-dimensional numerical model. The charateristics of the observed front can be reproduced if both, geostrophic forcing and boundary-layer processes, such as air-sea temperature difference, moisture content and cloud radiational cooling are taken into account. The development of the front under altered conditions is studied by the comparison of different simulations. The reason for the movement of the front is discussed refering to the mechanisms of geostrophic forcing and the forcing by surface friction. The analysis of the forces acting on the cold air mass shows that the Coriolis force is important at some distance behind the frontal head, but has little effect on the processes at the frontal head.With 13 Figures