Geoscience Reference
In-Depth Information
Figure 4.17
Mean precipitation (mm/yr) over (A) the oceans, (B) the land and (C) globally for December to February, June to August
and annually.
Source
: Peixoto and Oort (1983). From
Variations in the Global Water Budget
, ed. A. Street-Perrott, M. Beran and R. Ratciffe (1983), Fig. 23.
Copyright © D. Reidel, Dordrecht, by kind permission of Kluwer Academic Publishers.
and the occurrence of precipitation. However, a further
factor may be the effect of eddies, set up in the airflow
by the mountains, on the catch of rain gauges. Studies
in Bavaria at the Hohenpeissenberg Observatory show
that standard rain gauges may overestimate amounts by
about 10 per cent on the lee slopes and underestimate
them by 14 per cent on the windward slopes.
In the tropics and subtropics, maximum precipita-
tion occurs below the higher mountain summits, from
which level it decreases upward towards the crest.
Observations are generally sparse in the tropics, but
numerous records from Java show that the average ele-
vation of greatest precipitation is approximately 1200 m.
Above about 2000 m, the decrease in amounts becomes
quite marked. Similar features are reported from Hawaii
and, at a rather higher elevation, on mountains in East
Africa (see Chapter 11H.2). Figure 4.18A shows that,
despite the wide range of records for individual stations,
this effect is clearly apparent along the Pacific flank of
the Guatemalan highlands. Further north along the
