Mechanisms of Climate Variability - Natural Hazards - page 41

Timing of flood (F) and drought (D) in North America, northern China, Patagonia, the Nile valley, India and the coincidence with the
18.6 year lunar tide

Table 2.2

Lunar Canadian United States N. China Patagonian Nile in India

Maxima Prairies Great Plains Andes Africa

1583 1581D 1582D

1601 1601D 1600D 1606F

1620 1622D 1620D 1621F

1638 1640D 1640D 1637F

1657 1652F 1659D 1656F

1676 1674F 1678D 1675F

1694 1694F 1693F

1713 1712F 1710F 1713D

1731 1729F 1727F 1733D

1750 1752F 1752D 1750D

1768 1768F 1768D 1766D

1787 1786F 1784D 1789D

1806 1805F 1805D 1806F 1802D 1806D

1824 1823F 1824D 1823F 1822D 1822D

1843 1843F 1844D 1846D 1841D 1837D

1861 1859F 1861D 1862D 1864D
1880 1881F 1879D 1881D 1880D 1885D
1899 1900F 1901D 1900D 1895D 1902D 1902D
1918 1916F 1919D 1918D 1918F 1917F 1913F
1936 1932F 1935D 1935F 1937F 1936F 1939F
1955 1953F 1955D 1954F 1956F 1953F 1958F
1973 1975F 1975D 1974F 1973F 1975F 1976F
1991 1995F 1993F 1990F 1992F 1996F 1990F
Sources: Currie (1984) and various internet searches. Since 1980, plotted rainfall anomalies for each region using
http://climexp.knmi.nl/fieldplot.cgi?someone@somewhere+gpcp

CONCLUDING COMMENTS

hazards, the realization is that they represent insepa-
rable hazards that follow each other in time as night
does day. Not only are the two events linked, but their
occurrence is also remarkably coincident across the
globe. They are intricately connected to the Southern
Oscillation and other spatial cyclic phenomena such as
the North Atlantic and North Pacific Oscillations.
Other hazards - such as tropical and extra-tropical
cyclones, wave erosion, and land instability - are
also correlated to the Southern Oscillation, and thus
subject to prediction. At mid-latitudes in the northern
hemisphere, storminess is more important. Here, the
North Atlantic Oscillation is the controlling factor.
Similar influences may occur in western North
America due to changes in sea surface temperature in
the north Pacific.

The dominant factor controlling air movement across
the surface of the Earth is the movement of cold polar
air in the form of mobile polar highs from the poles
towards the equator. This drives global air circulation
and satisfies the requirement in the atmosphere to
balance the inequality in heating and cooling between
the equator and poles, respectively. The concept of
mobile polar highs implies that the climate of high
latitudes is the key to world climate and global climate
change. Superimposed upon this meridional exchange
are zonal processes controlled by ocean-atmosphere
interactions. Chief amongst these is the Southern
Oscillation. While droughts and floods have plagued
people throughout recorded history, and are probably
responsible for the greatest loss of life of any natural