Simultaneous evaluation of ice cloud microphysics and nonsphericity of the cloud optical properties using hydrometeor video sonde and radiometer sonde in situ observations

Abstract

This study utilizes hydrometeor sonde and radiometer sonde in situ observations to simultaneously evaluate ice cloud microphysics and radiative fluxes. In addition, the impact of nonsphericity and heterogeneous ice nucleation schemes on radiative fluxes are examined using a double-moment bulk cloud microphysics scheme on a midlatitude frontal system. The distribution of simulated outgoing longwave radiation (OLR) is systematically reduced by assuming the presence of columnar ice crystals instead of planar ice crystals because of the difference in the effective radii (the projected area) between the two shapes. However, the choice of the heterogeneous ice nucleation schemes drastically changes the distribution of OLR by modifying the number concentration of the cloud ice (N i ) (more than tenfold). The observed shortwave fluxes are useful for evaluating the simulated number concentration of cloud ice when nonspherical single scattering properties are used instead of spherical single scattering properties. The dependence of the asymmetry factor on the effective radius is the key to quantitatively estimating the ice cloud radiative forcing and determining the aerosol indirect effect on ice clouds. Based on the comparison of shortwave fluxes, the cloud microphysics scheme was found to underestimate the N i near the cloud base (a robust bias). A possible method of modifying the bias is discussed.

Impact of Precipitating Ice Hydrometeors on Longwave Radiative Effect Estimated by a Global Cloud‐System Resolving Model

“…In addition to the mass of hydrometeors (cloud water, rain, cloud ice, snow, and graupel), the double‐moment scheme implemented in NICAM predicts number concentration of hydrometeors. The cloud optical properties were calculated using a look‐up table of effective radii of hydrometeors, which are estimated using the mass and the number concentration (Seiki et al, ). The radiative effects of ice clouds simulated by NICAM with the double‐moment cloud microphysics scheme were evaluated by Seiki et al (, ).…”

“…The cloud optical properties were calculated using a look‐up table of effective radii of hydrometeors, which are estimated using the mass and the number concentration (Seiki et al, ). The radiative effects of ice clouds simulated by NICAM with the double‐moment cloud microphysics scheme were evaluated by Seiki et al (, ). Seiki et al () revealed that the simulated total ice amount, which includes cloud ice, snow, and graupel, is improved using the double‐moment scheme compared with simulations from NICAM, which uses a single‐moment cloud microphysics scheme.…”

Evaluation of Precipitating Hydrometeor Parameterizations in a Single-Moment Bulk Microphysics Scheme for Deep Convective Systems over the Tropical Central Pacific

“…Single-moment schemes that calculate only the mass concentrations of hydrometeors (e.g., Lin et al 1983) have been widely used for large-scale experiments and long-term CSRM simulations because of their ease of use and computational efficiency. Double-moment schemes can predict changes in hydrometeor number concentration and enable explicit calculation of nucleation processes related to indirect aerosol effects and potentially more consistent treatment of the radiation effects of cloud particles (Seiki et al 2014). Double-moment schemes can predict changes in hydrometeor number concentration and enable explicit calculation of nucleation processes related to indirect aerosol effects and potentially more consistent treatment of the radiation effects of cloud particles (Seiki et al 2014).…”

Evaluating Arctic cloud radiative effects simulated by NICAM with A‐train

“…Impacts of the nonsphericity on the active sensors were discussed in Hashino et al [] for this data set, and it turned out that the cloud microphysical diagnosis was robust in a qualitative sense due to the large model‐observation differences. Seiki et al [] evaluated the vertical profiles of LW and SW fluxes simulated with NICAM and the two‐moment scheme called NDW6 [ Seiki and Nakajima , ]. Although midlatitude cirrus clouds with optical thickness of about six were their target, the use of nonspherical single scattering parameters led to about 60 W m −2 decrease in SW downward fluxes at surface and about 100 W m −2 increase in SW upward fluxes at 16 km from the Mie approximation.…”

“…The SW CREs constitute valuable information to evaluate cloud optical properties. The importance of the SW arises because, compared to the LW, (1) clouds do not become optically opaque in the SW until higher values of liquid water path are reached [ Shupe and Intrieri, ] and (2) the SW broadband is more sensitive to the effective radius and number concentration of ice particles [e.g, Seiki et al, ]. Shupe and Intrieri [] introduced a simple radiative transfer model for the shortwave net cloud radiative effect at surface (CRE SW,SFC ).…”