Cairn Gorm weather station - link for the current wind speed

Deflation surfaces are most commonly associated with desert and coastal dune systems

Partly vegetated sand sheet, Ben Macdui

Remnants of a smooth, relict, protruding wind polished surface at 1270 m a.s.l., on a granite bedrock outcrop on Braeriach, Cairngorm Mountains. The person is pointing at a preserved wind polished surface (light-grey area), while weathering has removed any wind polish on adjoining rock surfaces (Christiansen, 2004).

Wind

The Cairngorms experience some of the highest wind speeds of the British Isles. Gusts over 100 mph may occur several times a year and the weather station recorded the highest UK wind speed in a gust of 173 mph in March 1986.

Erosion by strong winds creates deflation surfaces. The vegetation, soil and fine material debris is removed to leave an armoured surface where large clasts are embedded within a matrix of grit and sand. Remnants of the former vegetation cover sometimes occur and allow the former thickness of the regolith to be estimated. Grains of sand and fine gravel can be observed in motion during strong winds - sand blasting the vegetation and rock surfaces. The resting places of the transported debris are often unclear. Small sand sheets occur on the northern flank of Ben Macdui but the bulk of the debris seems not to accumulate as dunes or sheets. Some becomes temporarily resident in the snow pack, to thaw out in spring. Some probably finds its way into lochans and burn on valleys floors.

Deflation scars are the bare patches that result from opening up of the vegetation by wind-stripping. Wind stripes are lines of vegetation that alternate with bare ground (Bayfield, 1984). Wind crescents are arcuate patches of vegetated ground. All three types of pattern can be observed on the Cairngorms plateau.

A careful search has recently revealed wind-facetted blocks in the Cairngorms (Christiansen, 2004). The surfaces are identified from their smooth and polished surfaces, together with facets and grooves. Some wind effects are modern but the best developed forms probably date from the Loch Lomond Stadial. Examination of many surfaces between Glen Clova and the Cairngorms indicates a predominance of two wind directions at this time: northerly and southerly. It has been suggested previously by Ballantyne and Harris (1994) that the prevailing pressure systems during the last glaciation provided southerly winds in summer and northerly winds in summer.

High wind speeds are not restricted to the high tops. Goodier (Baxter and Goodier, 1990) described the swathe cut through the Scots' Pines of central Quoich by a great storm. In 1976 the pines were already long dead, bleached but preserved from rotting by being held off the ground by the spines of their branches. Seton Gordon suggested felling during the northerly gale of 1893; others related it to the Tay Bridge storm of 28th December 1879. Tree ring measurements could sort out that problem and provide a means to identify the major storms of the last few centuries.