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1. Introduction Aerosols—that is, the liquid and solid particulates suspended in the atmosphere—constitute an important atmospheric component not only by directly absorbing and scattering solar radiation and terrestrial thermal infrared emission, but also by affecting the water cycle through their indirect effect [i.e., acting as efficient cloud condensation nuclei (CCN) or ice nuclei (IN) ( Ramanathan et al. 2001 )]. Substantial uncertainties in our current knowledge of the aerosol impact on
1. Introduction Aerosols—that is, the liquid and solid particulates suspended in the atmosphere—constitute an important atmospheric component not only by directly absorbing and scattering solar radiation and terrestrial thermal infrared emission, but also by affecting the water cycle through their indirect effect [i.e., acting as efficient cloud condensation nuclei (CCN) or ice nuclei (IN) ( Ramanathan et al. 2001 )]. Substantial uncertainties in our current knowledge of the aerosol impact on
1. Introduction The stratospheric aerosol layer consists of submicrometer-sized particles composed primarily of liquid solutions of sulfuric acid and water, with traces of other materials, such as ammonium sulfates. The layer was first identified by Junge et al. (1961) ; hence, it is often referred to as the “Junge” layer. Many studies have been performed to explain the formation, growth, and removal of stratospheric particles (e.g., Castleman et al. 1974 ; Hofmann et al. 1976 ; Turco et al
1. Introduction The stratospheric aerosol layer consists of submicrometer-sized particles composed primarily of liquid solutions of sulfuric acid and water, with traces of other materials, such as ammonium sulfates. The layer was first identified by Junge et al. (1961) ; hence, it is often referred to as the “Junge” layer. Many studies have been performed to explain the formation, growth, and removal of stratospheric particles (e.g., Castleman et al. 1974 ; Hofmann et al. 1976 ; Turco et al
1. Introduction With some assumptions, the Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol algorithm can derive three primary products: the spectral aerosol optical depth, the effective radius of the aerosol, and the fraction of the total optical depth contributed by the fine mode aerosol ( Tanré et al. 1997 ). Some evaluation works on the MODIS aerosol retrieval over ocean have been done. For example, Remer et al. (2005 , 2006 ) reported that two-thirds of the retrieved aerosol
1. Introduction With some assumptions, the Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol algorithm can derive three primary products: the spectral aerosol optical depth, the effective radius of the aerosol, and the fraction of the total optical depth contributed by the fine mode aerosol ( Tanré et al. 1997 ). Some evaluation works on the MODIS aerosol retrieval over ocean have been done. For example, Remer et al. (2005 , 2006 ) reported that two-thirds of the retrieved aerosol
1. Introduction Aerosol particles affect the climate of the earth directly by scattering and absorbing solar radiation and indirectly by affecting cloud microphysical properties ( Bréon et al. 2002 ) and cloud lifetime. Although their net radiative effect may compensate for increases in the effects of greenhouse gases, the current magnitude and even the regional sign of their net effect remains uncertain ( Forster et al. 2007 ). The constellation of National Aeronautics and Space Administration
1. Introduction Aerosol particles affect the climate of the earth directly by scattering and absorbing solar radiation and indirectly by affecting cloud microphysical properties ( Bréon et al. 2002 ) and cloud lifetime. Although their net radiative effect may compensate for increases in the effects of greenhouse gases, the current magnitude and even the regional sign of their net effect remains uncertain ( Forster et al. 2007 ). The constellation of National Aeronautics and Space Administration
1. Introduction Atmospheric aerosol, mainly comprising sulfate, nitrate, ammonium, black carbon (BC), organic carbon (OC), dust, and sea salt, is generated from primary anthropogenic and natural emissions as well as by secondary transformation. Aerosol has impacts on radiative transfer directly through scattering and absorbing solar radiation and indirectly by modifying microphysical properties of clouds, thereby exerting a cooling or heating effect on the planet ( Rosenfeld et al. 2008
1. Introduction Atmospheric aerosol, mainly comprising sulfate, nitrate, ammonium, black carbon (BC), organic carbon (OC), dust, and sea salt, is generated from primary anthropogenic and natural emissions as well as by secondary transformation. Aerosol has impacts on radiative transfer directly through scattering and absorbing solar radiation and indirectly by modifying microphysical properties of clouds, thereby exerting a cooling or heating effect on the planet ( Rosenfeld et al. 2008
1. Introduction Accurate sampling of aerosol particles from aircraft requires appropriately designed inlets that can representatively sample particles from the freestream and transport them to the measurement devices in the cabin. In clear air, this is often achieved using isokinetic sampling with diffuser-style inlets, where the sample velocity is matched with the freestream velocity. In clouds, accurate sampling of nonactivated or interstitial aerosol is complicated by the breakup or shatter
1. Introduction Accurate sampling of aerosol particles from aircraft requires appropriately designed inlets that can representatively sample particles from the freestream and transport them to the measurement devices in the cabin. In clear air, this is often achieved using isokinetic sampling with diffuser-style inlets, where the sample velocity is matched with the freestream velocity. In clouds, accurate sampling of nonactivated or interstitial aerosol is complicated by the breakup or shatter
1. Introduction The contribution of aerosol particles to the earth’s radiative balance is a major uncertainty in modeling long-term global climate ( Denman et al. 2007 ). A particular challenge in climate modeling is in accurately representing the indirect effect, that is, the aerosol interaction with water vapor to form clouds ( Andreae and Rosenfeld 2008 ; Seinfeld and Pandis 2006 ). In global climate models, for simplicity of numerical calculations, aerosol–cloud processes are often just
1. Introduction The contribution of aerosol particles to the earth’s radiative balance is a major uncertainty in modeling long-term global climate ( Denman et al. 2007 ). A particular challenge in climate modeling is in accurately representing the indirect effect, that is, the aerosol interaction with water vapor to form clouds ( Andreae and Rosenfeld 2008 ; Seinfeld and Pandis 2006 ). In global climate models, for simplicity of numerical calculations, aerosol–cloud processes are often just
1. Introduction Observational-based studies have shown that the presence of thick aerosol plumes can significantly attenuate surface-reaching solar energy, thereby altering the heat budget and, perhaps, regional weather patterns. For instance, noticeable high biases in numerical weather prediction (NWP) model forecast near-surface air temperatures have been reported with the presence of heavy smoke plumes (e.g., Westphal and Toon 1991 ; Robock 1991 ; Zhang et al. 2016 ). Despite demonstrated
1. Introduction Observational-based studies have shown that the presence of thick aerosol plumes can significantly attenuate surface-reaching solar energy, thereby altering the heat budget and, perhaps, regional weather patterns. For instance, noticeable high biases in numerical weather prediction (NWP) model forecast near-surface air temperatures have been reported with the presence of heavy smoke plumes (e.g., Westphal and Toon 1991 ; Robock 1991 ; Zhang et al. 2016 ). Despite demonstrated
1. Introduction Anthropogenic aerosols from burning fossil fuels and biomass affect the earth’s radiation balance in multiple ways. They scatter and absorb shortwave (SW) and longwave (LW) radiation in the clear sky (the direct effect; e.g., Haywood and Ramaswamy 1998 ). Atmospheric warming exerted by absorbing aerosols (e.g., black carbon) facilitates dissipation of clouds through evaporating droplets (the semidirect effect; e.g., Hansen et al. 1997 ). Water-soluble aerosol particles (e
1. Introduction Anthropogenic aerosols from burning fossil fuels and biomass affect the earth’s radiation balance in multiple ways. They scatter and absorb shortwave (SW) and longwave (LW) radiation in the clear sky (the direct effect; e.g., Haywood and Ramaswamy 1998 ). Atmospheric warming exerted by absorbing aerosols (e.g., black carbon) facilitates dissipation of clouds through evaporating droplets (the semidirect effect; e.g., Hansen et al. 1997 ). Water-soluble aerosol particles (e
.g., Carlton et al. 2018 ) and debated with studies proposing it to be a result of any or all of the following: “dimming” due to aerosols ( Leibensperger et al. 2012 ; Mickley et al. 2012 ; Saxena and Yu 1998 ; Tosca et al. 2017 ; Silvern et al. 2017 ; Zheng et al. 2020 ); an increase in cloudiness, precipitation, and soil moisture variability ( Napton et al. 2010 ; Liang et al. 2006 ; Yu et al. 2014 ; Cusworth et al. 2017 ); variability of sea surface temperatures (SSTs) in both the Atlantic and
.g., Carlton et al. 2018 ) and debated with studies proposing it to be a result of any or all of the following: “dimming” due to aerosols ( Leibensperger et al. 2012 ; Mickley et al. 2012 ; Saxena and Yu 1998 ; Tosca et al. 2017 ; Silvern et al. 2017 ; Zheng et al. 2020 ); an increase in cloudiness, precipitation, and soil moisture variability ( Napton et al. 2010 ; Liang et al. 2006 ; Yu et al. 2014 ; Cusworth et al. 2017 ); variability of sea surface temperatures (SSTs) in both the Atlantic and
