Introduction to special section: Outstanding problems in quantifying the radiative impacts of mineral dust

Abstract

Abstract. This paper provides an introduction to the special section of the Journal of Geophysical Research on mineral dust. We briefly review the current experimental and theoretical approaches used to quantify the dust radiative impacts, highlight the outstanding issues, and discuss possible strategies to overcome the emerging problems. We also introduce the contributing papers of this special section. Despite the recent notable advances in dust studies, we demonstrate that the radiative effects of dust remain poorly quantified due to both limited data and incomplete understanding of relative physical and chemical processes. The foremost needs are (1) to quantify the spatial and temporal variations of dust burden in the atmosphere and develop a predictive capability for the size-and composition-resolved dust particle distribution; (2) to develop a quantitative description of the processes that control the spatial and temporal variabilities of dust physical and chemical properties and radiative effects; (3) to develop new instrumentation (especially to measure the dust particle size distribution in a wide range from about 0.01 gm to 100 gm, scattering phase function and light absorption by dust particles); and (4) to develop new techniques for interpreting and merging the diverse information from satellite remote sensing, in situ and ground-based measurements, laboratory studies, and model simulations. Because dust distribution and effects are heterogeneous, both spatially and temporally, a promising strategy to advance our knowledge is to perform comprehensive studies at the targeted regions affected by mineral dust of both natural and anthropogenic origin.

Columnar aerosol single‐scattering albedo and phase function retrieved from sky radiance over the ocean: Measurements of Saharan dust

“…Since mean aerosol optical depths of many species (e.g., Arabian and Asian mineral dust, biomass burning aerosols from southwest Africa) fall between 0.3 and 0.5 during peak seasonal activity [Husar et al, 1997], successful AERONET retrievals require periods of unusually strong aerosol activity. The Wang-Gordon algorithm can thus serve as a valuable supplement to aerosol characterization studies, particularly during closure experiments for which success relies on obtaining an overdetermined set of aerosol properties [Ogren, 1995;Sokolik et al, 2001] within the allotted time period. The insensitivity of the algorithm to particle shape also promises to be useful in assessing the accuracy of nonspherical models used to deduce the optical properties of airborne mineral dust [Dubovik et al, 2002b].…”

Physico‐chemical and optical properties of Sahelian and Saharan mineral dust: in situ measurements during the GERBILS campaign

“…By scattering and absorbing solar and terrestrial radiation, mineral dust has a direct impact on climate (Sokolik et al, 2001). At a global scale, the direct radiative effect of mineral dust from natural and anthropogenic sources at the top of the atmosphere (TOA) is between −0.56 and +0.1 W m −2 (Forster et al, 2007).…”

Origin and pathways of the mineral dust transport to two Spanish EARLINET sites: Effect on the observed columnar and range-resolved dust optical properties

“…Dust aerosols impact the radiation budget of the Earth-atmosphere system, both directly by scattering and absorbing solar and terrestrial thermal radiation, and also indirectly by modifying cloud optical properties and lifetimes. The shortwave radiative forcing of dust aerosols can be either positive or negative, whilst the longwave radiative forcing is always positive (Tegen et al, 1996;Sokolik et al, 2001;Ramanathan et al, 2007;Perrone and Bergamo, 2011;Piedeherro et al, 2014;Obregon et al, 2015).…”