How the Inhomogeneity of Wet Sea Salt Aerosols Affects Direct Radiative Forcing

Abstract

Sea salt aerosols were assumed to be homogeneous spheres in most climate models. However, observations show that sea salt particles are inhomogeneous during the deliquesce and crystallization processes. Using a two‐layer sphere model, we found that backscattering of solar radiation associated with sea salts is underestimated in homogeneous sea salt models. The Community Earth System Model is used to assess the inhomogeneity effect on direct radiative forcing. For global climate model simulation, the inhomogeneity effect on radiative transfer is found to be small as high RHs over widespread oceans suppress the impact of inhomogeneity. On the other hand, in coastal regions, the inhomogeneity effect can cause up to 10% radiative forcing difference of sea salt aerosols. The inhomogeneity effect of sea salt aerosols has to be considered over coastal regions, especially in the Mediterranean, Australia, and the eastern coast of South America.

Modeling Optical Properties of Non‐Cubical Sea‐Salt Particles

“…In that study, superellipsoids resembling rounded cubes, spheres, and rounded octahedra as well as distortions of these base solids by changing the aspect ratio were considered. Sea‐salt aerosol with a water coating was investigated in regard to the depolarization ratio (Bi, Lin, Wang, et al., 2018), and in regard to the impact on radiative forcing (Wang et al., 2019).…”

Capability of Superspheroids for Modeling PARASOL Observations Under Dusty‐Sky Conditions

“…(2018), only superspheroids with roundness parameter being equal to or greater than 1.0 were employed in simulations for modeling dust aerosols. Note that superspheroids with the roundness parameter (<1.0; not shown) were found useful for modeling dry sea‐salt aerosols (Bi, Lin, Wang, et al., 2018; Z. Wang et al., 2019). Because the superspheroidal model has one more degree of freedom as compared to the spheroidal model, the superspheroidal model allows the possibility to constrain the particle geometry in a relatively large shape space.…”

“…According to Lin et al (2018), only superspheroids with roundness parameter being equal to or greater than 1.0 were employed in simulations for modeling dust aerosols. Note that superspheroids with the roundness parameter (<1.0; not shown) were found useful for modeling dry sea-salt aerosols (Bi, Lin, Wang, et al, 2018;Z. Wang et al, 2019).…”

“…Attention should be called to the fact that the complexity of the dust model's geometry often requires numerous computer resources and time for optical computation, which might be one of the difficulties in applying complicated dust models to generalized applications. The superspheroidal model has been recently proposed for optical modeling studies of dust aerosols (Bi, Lin, Wang, et al., 2018; Lin et al., 2018; Tang et al., 2019) and studies of the optical properties and radiative forcing of sea‐salt aerosols (Bi, Lin, Wang, et al., 2018; Z. Wang et al., 2019). The superiority of superspheroidal model to the spheroidal model in modeling scattering phase matrices of different dust samples from the Amsterdam‐Granada Light Scattering Database (Muñoz et al., 2012) has been investigated in Lin et al.…”

Particle Shape Impact on the Radiative Forcing Efficiency Estimated from Single Levitated (NH4)2SO4 Particles

“…In marine environments, the influence of the RH is crucial to calculate the morphology and the refractive index of sea salts. Wang et al [14] reported that the inhomogeneity effect can cause up to 10% radiative forcing of sea salts. Therefore, an accurate assessment of the impact of inorganic salt shapes on optical properties and hence on the radiation field is still demanded.…”