Climate, Climate Variability and Impacts in the Mediterranean Area: An Overview
51
higher spatial resolution than presently provided by the International Satellite Cloud
Climatology Project (ISCCP). In different regions of the Medi terranean the spectral
atmospheric transmission has been measured and also regional networks exist. It
would be necessary to intensify these measurements with modern equipment at
"Anchor Stations" distributed around the Mediterranean, to evaluate these data with
a standardized procedure and to compile these data into a central archive to generate
a more complete picture for the whole basin.
There may also exist another climate relevant link between carbon dioxide and
desert aerosols which is not yet explored. It is known that the uptake of CO 2 by the
oceans increases with its iron content. Into the Mediterranean Sea continuously
Saharan minerals are precipitated among which are iron containing minerals. Does
this lead to an additional dumping of CO 2 into the Mediterranean Sea?
6 Will Mediterranean Water Resources and Vegetation
Sustain Dramatic Climate Changes?
6.1 The Search for Long Term Variability and Trends in Operational
Precipitation Data
Some features of the Mediterranean climate and its spatial variability have been
discussed in the second section of this chapter and in the third section the climate
development prior to the establishment of the operational measuring network, the
"instrumental era", was addressed. Here now more recent studies are reported of
temporal variability primarily of precipitation. The latest results of Mediterranean
climatologists are then presented in Chapters 4 and 5.
Maheras (1988) investigated the changes of precipitation conditions in the
western Mediterranean basin from 1891 to 1985 by means of a principal component
analysis. Two principal moist periods occurred from 1901 to 1921 and 1930 to 1941
with dry periods in between and 1942 to 1954. 1980 again a dry period began. This
indicates a periodicity of about 20 years. The wet periods coincide with weaker zonal
circulation and the dry periods with stronger zonal circulation. The analysis was
expanded retrospectively by Rodrigo et al. (2000) for Andalusia to 1500 AD where
three major long lasting dry periods, 1501-1589, 1650-1775, and 1938-1997 could
be identified and periodicities of 2.1, 3.5, 7-9, and 16.7 years have been found.
Droughts are related to high positive NAO indices and floods to negative NAO
values.
With respect to the whole basin Kutiel and Maheras (1998) and Maheras,
Xoplaki, and Kutiel (1999) concluded that there exists a complicated pattern of
hydric anomalies throughout the Mediterranean basin. There can be positive as well
as negative excursions from average (i) basin-wide, (ii) primarily in the west, (iii)
strong in the west and east but weak in the central parts, or (iv) positive in the east
and weaker in the western part. Temperatures of Malta, Athens and Jerusalem are
51
higher spatial resolution than presently provided by the International Satellite Cloud
Climatology Project (ISCCP). In different regions of the Medi terranean the spectral
atmospheric transmission has been measured and also regional networks exist. It
would be necessary to intensify these measurements with modern equipment at
"Anchor Stations" distributed around the Mediterranean, to evaluate these data with
a standardized procedure and to compile these data into a central archive to generate
a more complete picture for the whole basin.
There may also exist another climate relevant link between carbon dioxide and
desert aerosols which is not yet explored. It is known that the uptake of CO 2 by the
oceans increases with its iron content. Into the Mediterranean Sea continuously
Saharan minerals are precipitated among which are iron containing minerals. Does
this lead to an additional dumping of CO 2 into the Mediterranean Sea?
6 Will Mediterranean Water Resources and Vegetation
Sustain Dramatic Climate Changes?
6.1 The Search for Long Term Variability and Trends in Operational
Precipitation Data
Some features of the Mediterranean climate and its spatial variability have been
discussed in the second section of this chapter and in the third section the climate
development prior to the establishment of the operational measuring network, the
"instrumental era", was addressed. Here now more recent studies are reported of
temporal variability primarily of precipitation. The latest results of Mediterranean
climatologists are then presented in Chapters 4 and 5.
Maheras (1988) investigated the changes of precipitation conditions in the
western Mediterranean basin from 1891 to 1985 by means of a principal component
analysis. Two principal moist periods occurred from 1901 to 1921 and 1930 to 1941
with dry periods in between and 1942 to 1954. 1980 again a dry period began. This
indicates a periodicity of about 20 years. The wet periods coincide with weaker zonal
circulation and the dry periods with stronger zonal circulation. The analysis was
expanded retrospectively by Rodrigo et al. (2000) for Andalusia to 1500 AD where
three major long lasting dry periods, 1501-1589, 1650-1775, and 1938-1997 could
be identified and periodicities of 2.1, 3.5, 7-9, and 16.7 years have been found.
Droughts are related to high positive NAO indices and floods to negative NAO
values.
With respect to the whole basin Kutiel and Maheras (1998) and Maheras,
Xoplaki, and Kutiel (1999) concluded that there exists a complicated pattern of
hydric anomalies throughout the Mediterranean basin. There can be positive as well
as negative excursions from average (i) basin-wide, (ii) primarily in the west, (iii)
strong in the west and east but weak in the central parts, or (iv) positive in the east
and weaker in the western part. Temperatures of Malta, Athens and Jerusalem are