Geoscience Reference
In-Depth Information
Chapter 13
Impact of Dust Radiative Forcing upon Climate
Ron L. Miller, Peter Knippertz, Carlos Pérez García-Pando,
Jan P. Perlwitz, and Ina Tegen
Abstract
Dust aerosols perturb the atmospheric radiative flux at both solar and
thermal wavelengths, altering the energy and water cycles. The climate adjusts
by redistributing energy and moisture, so that local temperature perturbations,
for example, depend upon the forcing over the entire extent of the perturbed
circulation. Within regions frequently mixed by deep convection, including the
deep tropics, dust particles perturb the surface air temperature primarily through
radiative forcing at the top of the atmosphere (TOA). Many models predict that dust
reduces global precipitation. This reduction is typically attributed to the decrease
of surface evaporation in response to dimming of the surface. A counterexample
is presented, where greater shortwave absorption by dust increases evaporation
and precipitation despite greater dimming of the surface. This is attributed to the
dependence of surface evaporation upon TOA forcing through its influence upon
surface temperature and humidity. Perturbations by dust to the surface wind speed
and vegetation (through precipitation anomalies) feed back upon the dust aerosol
concentration. The current uncertainty of radiative forcing attributed to dust and the
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