Aeolian systems - Fundamentals of the Physical Environment - page 395

(a) (b)

Dominant wind

S

S

R

B

Saltation (S), ballistic impact (B) and reptation (R)

BARCHAN LINGUOID

moist sand

Impacts continue; small mound forms where moist sand traps
particles

PARABOLIC AKLÉ

N o do m inant wind

Increased number of grains one 'hop' downwind causes development of
second mound; regularly-spaced ripples start to form.

SEIF RHOURD

Figure 16.5 The formation and character of aeolian bedforms: (a) micro-scale ripples and (b) macro-scale dunes. Most of the
latter may be superimposed on draa or megadunes.
Source: Partly after Collinson (1986)

(a)

+1

0

Medieval
Warm Epoch

-1

“Little Ice Age”

15

10

5
0

AD1000 1200 1400 1600 1800

(b)

+6

+5

+4

+3

+2

+1

+1.0

+0.5

Figure 16.6 Temperature and storminess in north-west
Europe. (a) The late medieval and pre-industrial period ( AD
1000-1850), from proxy and documentary records. The
broken line shows the long-term 'mean temperature'. (b)
Observed and forecast changes 1850-2100, from direct
observation and AOGCMs. Storm track activity is shown in
geopotential metres (gpm) and the broken line shows the
climate trend. Temperature forecasts after 2000 show the
'envelope of uncertainty' dependent on the nature and extent
of human and natural systems responses.
Source: (a) Partly after Lamb (1982), (b) partly after IPCC (2001)

0

60

55

50

45

40

AD1850 1900 1950 2000 2050 AD2100