Atmospheric aerosols and trace gases are a highly relevant component of the
climate system affecting atmospheric radiative transfer and the hydrologic
cycle. In arid and semi-arid regions, where cloud cover is often low and
precipitation is generally scarce and sporadic, the driving processes accounting
for the production, loss and transport of atmospheric constituents are often
distinctly different from other climates. In arid regions, the same
circulation dynamics that suppress cloud formation can be responsible for
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