xviii
Introduction
In order to establish the importance of latitudinal variations in climatic
factors for the structure of these rainforests , Lawford analyzes transects
of coastal patterns of temperature, precipitation, and other hydroclimatic
variables along the western coasts of North and South America . Although
the gross features of these patterns are similar between continents,
there are many significant regional and local differences that control
ecosystems at the landscape and smaller scales. For example , the displacement of the climatic equator northward from the geographical equator
and the dramatic influence of the Andes mountains on local atmospheric
circulation patterns led to broader bands of arid and semiarid conditions
in Chile and Peru than in North America. Upper-air circulation patterns
in the Southern Hemisphere are more consistent from season to season ,
leading to more stable zones of high precipitation along the west coast of
South America . Although the estimates of hydroclimatic fields presented
by Lawford have some inherent limitations , the general character of the
fields reflects the large-scale controls on climate. However, it must be
recognized that better models and more strategic data collection activities
are needed to address the issues of land-atmosphere-biosphere links in
these coastal areas.
McBean provides a more detailed examination of the dynamic controls
on climate over the area of the western coast stretching from 30°N to
60
0N. He notes that variability occurs on different space and time scales,
with response times being dependent on the spatial scale of the phenomena
being considered and the medium (e.g. , atmosphere or ocean) in which
the variation is occurring. The large-scale linkages between the atmospheric circulation pattern and the topography are reflected in the complex
precipitation patterns observed along the coast. Differences in the dominant circulation regimes with latitude also influence the coastal oceanography. Upwelling of cold subsurface water is common between 30
0 N
and 45°N due to the dominant offshore pressure pattern. Father north ,
upwelling is much more irregular.
Benbow continues the theme of atmosphere-ocean interactions, associating upwelling areas with certain climate influences, including those
arising from the production of dimethylsulfide. This volatile sulfur compound, which is produced by marine phytoplankton, leads to the production
of cloud condensation nuclei with high sulfide content. Benbow assesses
the importance of phytoplankton-zooplankton interactions for DMS
(dimethylsulfide) production. The major effects of atmospheric releases
of DMS on climate include enhanced production of cloud and increases in
the concentration of sulfur compounds in precipitation leading to differential chemical inputs to coastal forests.
Hedin and Hetherington document the differences between the atmospheric and geological inputs to coastal forests. In the Chilean rainforests,
the inputs of sea-salt aerosols coupled with the low rates of weathering
constitute a major biogeochemical constraint on forests. In contrast,
Introduction
In order to establish the importance of latitudinal variations in climatic
factors for the structure of these rainforests , Lawford analyzes transects
of coastal patterns of temperature, precipitation, and other hydroclimatic
variables along the western coasts of North and South America . Although
the gross features of these patterns are similar between continents,
there are many significant regional and local differences that control
ecosystems at the landscape and smaller scales. For example , the displacement of the climatic equator northward from the geographical equator
and the dramatic influence of the Andes mountains on local atmospheric
circulation patterns led to broader bands of arid and semiarid conditions
in Chile and Peru than in North America. Upper-air circulation patterns
in the Southern Hemisphere are more consistent from season to season ,
leading to more stable zones of high precipitation along the west coast of
South America . Although the estimates of hydroclimatic fields presented
by Lawford have some inherent limitations , the general character of the
fields reflects the large-scale controls on climate. However, it must be
recognized that better models and more strategic data collection activities
are needed to address the issues of land-atmosphere-biosphere links in
these coastal areas.
McBean provides a more detailed examination of the dynamic controls
on climate over the area of the western coast stretching from 30°N to
60
0N. He notes that variability occurs on different space and time scales,
with response times being dependent on the spatial scale of the phenomena
being considered and the medium (e.g. , atmosphere or ocean) in which
the variation is occurring. The large-scale linkages between the atmospheric circulation pattern and the topography are reflected in the complex
precipitation patterns observed along the coast. Differences in the dominant circulation regimes with latitude also influence the coastal oceanography. Upwelling of cold subsurface water is common between 30
0 N
and 45°N due to the dominant offshore pressure pattern. Father north ,
upwelling is much more irregular.
Benbow continues the theme of atmosphere-ocean interactions, associating upwelling areas with certain climate influences, including those
arising from the production of dimethylsulfide. This volatile sulfur compound, which is produced by marine phytoplankton, leads to the production
of cloud condensation nuclei with high sulfide content. Benbow assesses
the importance of phytoplankton-zooplankton interactions for DMS
(dimethylsulfide) production. The major effects of atmospheric releases
of DMS on climate include enhanced production of cloud and increases in
the concentration of sulfur compounds in precipitation leading to differential chemical inputs to coastal forests.
Hedin and Hetherington document the differences between the atmospheric and geological inputs to coastal forests. In the Chilean rainforests,
the inputs of sea-salt aerosols coupled with the low rates of weathering
constitute a major biogeochemical constraint on forests. In contrast,