OROGRAPHIC CIRRUS GENERATED BY ICELAND AND THE FAEROE ISLANDS - 4-6 MAY 1993

Fig. 1 provides two clear examples of orographically generated cirrus cloud, north-east of the Faeroes in 1(a) and north-east of Iceland in 1(b). Animated hourly images show the south-western edges of these clo ud masses to be almost stationary, whilst filaments within the cirrus stream away to the north and north-east wavering occasionally to the l eft or right. The appearance resembles that of a flame, or a flag bein g blown by the wind. Insets in Fig. 1 show UK Met. Office limited area model (LAM) delta for times close to those of the respective images. The south-westerly upper flow is broadly consistent with the location and behaviour of the cirrus. It should be appreciated at the outset th at most (if not all) theories and numerical simulations relating to or ographic cirrus assume orographic barriers of infinite length. This br ief study will relate cirrus features to individual peaks, and conside r the effect of such peaks on downstream flow; in this respect the wor k is new. For this reason the results in sections 2, 3 and 5, which dr aw upon past work, must necessarily be treated with some caution.