A survey of the vegetation of Ben Nevis - Scottish Natural Heritage

temperature was 1.6°C; the mean minimum temperature –2.2°C, showing that even on the summit the
climate is oceanic, with a small annual range in temperature. Only in June, July, August and September was
the mean monthly minimum temperature above freezing. The lowest recorded temperature at the observatory
was –17.4°C on 6 January 1884. The summit of the Ben is so high that it may, on occasions, be above
the level of temperature inversions. Low cloud is often trapped below the inversion layer, so there are days
in which Fort William and the surrounding glens are clothed in heavy cloud while the summit of Ben Nevis
is sunny and unusually dry. The total annual precipitation recorded for Ben Nevis in 1883–1904 was
4084mm – twice that recorded on low ground in the same part of Scotland. The strongest winds recorded
on Ben Nevis were estimated to exceed 113 knots and, interestingly, were from the south-east. This is
probably because westerly winds are deflected round to the south, and increased in force, when they meet
the high barrier of the western Highland hills. The annual total of sunshine in 1883–1904 was just 736m
on Ben Nevis, and the percentage of the time that the observatory was in mist or low cloud varied from
about 78% in winter to about 55% in early summer.
1.4 Nomenclature
Scottish Natural Heritage Commissioned Report No. 090 (ROAME No. F02LD01)
Nomenclature in this report follows Stace (1997) for vascular plants, Blockeel & Long (1998) for bryophytes,
and Purvis et al. (1992) for lichens. Place names are those on the Ordnance Survey 1:10,000 maps.
Plant communities (eg U10) and sub-communities (eg U10c) are those of the National Vegetation Classification
(NVC) (Rodwell 1991a, 1991b, 1992, 1995), supplemented by additional codes for vegetation not
described by the NVC.
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