Two case studies of winter continental‐type water and mixed‐phase stratocumuli over the sea 2. Absorption of solar radiation

Abstract

[1] We have carried out airborne experiments on cloud-radiation interactions for wintertime boundary layer clouds over the East China Sea and the Japan Sea in January 1999 as part of the Japanese Cloud and Climate Study (JACCS) program. By means of collocated and synchronized flights of two instrumented aircraft, flying above and below the cloud layer, respectively, we directly measured the visible and near-infrared (IR) solar absorption for two cases of stratiform clouds: one featuring supercooled water stratocumulus cloud polluted by continental aerosols observed on 21 January and one featuring highly inhomogeneous, mixed-phase stratocumulus clouds observed on 30 January. The former cloud layer, with a geometrical thickness of about 500 m (optical thickness of about 30), absorbed substantial (6%) and significant (21%) amounts of solar radiation in the visible and near-IR bands, respectively. For the latter mixed-phase cloud, on an average over a long flight distance, the visible-band solar absorption was almost zero, while the near-IR-band absorption was about 24% for the cloud layer with a mean thickness of 1.3 km. The results indicate no sign of the so-called anomalous solar absorption for either cloud case. Through radiative transfer simulations for reasonable aerosol-cloud models, along with back trajectory analysis, the visible-band solar absorption by the aerosol-polluted cloud on 21 January was attributed to absorbing aerosols from continental East Asia. The simulation study also suggests that anthropogenic water-soluble aerosols, as well as soil-dust particles, may cause appreciable visible absorption by cloud particles, resulting in an enhanced solar heating in the boundary layer cloud.

Two case studies of winter continental‐type water and mixed‐phase stratocumuli over the sea 1. Microphysical and optical properties

“…The scattering phase functions measured for the first time for mixed‐phase boundary layer cloud will serve as unique and valuable data set for implementation and validation of an iterative method, based on the bi‐component (water and ice crystals) representation of cloud composition, for the retrieving of the microphysical properties. The measured visible and near‐infrared solar absorption is discussed in detail in the companion of this paper [ Asano et al , 2002] with the interpretation of the results from a numerical simulation study.…”

“…The results are attempted to provide some basic information on the structural, microphysical and optical properties with the intention of obtaining some insight into cloud radiative transfer problem and into the inference of cloud composition from satellite information. Subsequent measured visible and near‐infrared solar absorption are discussed with details in the companion of this paper [ Asano et al , 2002] with the interpretation of the results from a numerical simulation study.…”

Assessment of cloud optical parameters in the solar region: Retrievals from airborne measurements of scattering phase functions

“…The measurements used in the study are based on the in situ angular scattering coefficient measurements performed with the Polar Nephelometer [ Gayet et al , 1997; Crépel et al , 1997]. The experimental data have been obtained during three campaigns, namely, Avion de Recherche Atmosphérique et de Télédétection (ARAT'97) [ Duroure et al , 1998], CIRRUS'98 [ Durand et al , 1998], and the Japanese Cloud and Climate Study (JACCS'99) [ Asano et al , 2002; Gayet et al , 2002a], which were carried out from Clermont‐Ferrand (central part of France), Tarbes (southwest of France), and over the Sea of Japan, respectively. Collectively, these campaigns present the advantage of merging three large sets obtained in a wide variety of meteorological conditions.…”

Seasonal Trends of Atmospheric Ice Nucleating Particles Over Tokyo

“…Aerosol particles in Asian outflow are thought to be one of possible major sources of the global INP load and have large impacts on aerosol‐cloud‐precipitation interactions on local, regional, and global scales. For example, aircraft measurements around the Japan Islands by Asano et al (2002) and Gaynet et al (2002) revealed the occurrence of boundary‐layer mixed‐phase clouds at temperatures above −15°C during a wintertime cold‐air outbreak event from the Asian continent (Asano et al, 2002; Gaynet et al, 2002), indicating the existence of certain efficient INPs in Asian continental outflow. Ground‐based in situ and/or lidar measurements in China (Bi et al, 2019), Japan (Isono et al, 1959; Murayama et al, 2001; Sakai et al, 2004), and the United States (Ault et al, 2011; Creamean et al, 2013; Pratt et al, 2009; Sassen, 2002) have suggested the importance of long‐range transported dust particles and/or primary biological aerosol particles (PBAPs) such as fungal spores and bacteria from the Asian continent for heterogeneous ice nucleation and subsequent precipitation processes.…”