Radiative Properties of Mid-latitude Frontal Ice-Clouds Observed by the Shortwave and Longwave Radiometer-Sondes

Abstract

In the Japanese Cloud and Climate Study (JACCS) cirrus experiment, simultaneous measurements of cloud radiative and microphysical properties were conducted by using the combined-sonde (radiometersonde þ hydrometeor-video-sonde (HYVIS)) observation system at the Meteorological Research Institute (MRI), located at (36.05 N, 140.13 E) in Tsukuba, Japan, during early summer seasons from 1995 to 1999. We have analyzed the radiative properties of frontal ice-clouds observed by the shortwave and longwave radiometer-sondes (Asano et al. 2004). To interpret the observed radiative flux profiles, we have also performed radiative transfer calculations for horizontally homogeneous atmospheric models, where the single-scattering properties of ice-clouds were computed by anomalous diffraction theory for ice-crystals observed by HYVIS. On an average of the observed frontal ice-clouds, the shortwave reflectance, transmittance and absorptance were estimated to be 0.41 G 0.03, 0.51 G 0.06, and 0.08 G 0.09, respectively, for the averaged ice-cloud layer with a mean visible optical thickness of 4.6 and a mean geometrical thickness of 5.4 km (mean volume extinction coefficient of 0.85 km À1 ). The ice-clouds were significantly heated by absorption of solar radiation in daytime. On the other hand, the mean effective emittance was estimated to be about 0.86 G 0.37, showing that the frontal ice-clouds never acted as blackbody for longwave radiation. The lower parts of ice-cloud layers were heated by absorption of longwave radiation from the surface and the atmosphere below the ice-clouds, while the upper parts were cooled by emission of longwave radiation to space. The shortwave and longwave heating profiles could make the daytime ice-cloud layers thermodynamically unstable.

Assessing the impact of the Kuroshio Current on vertical cloud structure using CloudSat data

“…4i and j). Radiative heating occurred due to shortwave radiation inside the cloud, while radiative cooling occurred due to longwave radiation around the cloud top (Yoshida et al, 2004). Shortwave cloud radiative heating and longwave cloud radiative cooling were both strong at the higher altitudes over the Kuroshio (126-128 • E, Fig.…”

Effects of the Vertical Profiles of Cloud Droplets and Ice Particles on the Visible and Near-Infrared Radiative Properties of Mixed-Phase Stratocumulus Clouds

“…The solar radiation budget and the cloud radiative properties (reflectance, transmittance, and absorptance) have been computed for the assumed cloudatmosphere column between the altitudes of 3.5 km (C404 flight level) and 0.3 km (B200 flight level). A description of the radiative transfer scheme used in this study can be found in Yoshida et al (2004), but with some modifications described below. The temperature and humidity profiles measured through the aircraft experiment were employed up to 2.5 km, and above 2.5 km they were adjusted to the radiosonde profile measured at the JMA Yonago Observatory (35.26 N,133.21 E) on that morning at 09:00 (LST).…”

“…On the other hand, the scattering properties of ice particles (including snow crystals) were calculated by anomalous diffraction theory (ADT) with a gamma size distribution (Mitchell et al 1996). By using the experimental area-/massdimensional relationships for various shapes of ice particles, the ADT can calculate the extinction and absorption coefficients of ice particles more exactly than Mie-theory can do for ice spheres with equivalent-area and/or volumes (e.g., Yoshida et al 2004). Here, we assumed ice crystals of polycrystal shape from the ice particle images taken by the 2D-C probe (twodimensional optical array spectrometer) onboard B200 (see Fig.…”

Development of a Radiometer-Sonde for Simultaneously Measuring the Downward and Upward Broadband Fluxes of Shortwave and Longwave Radiation

“…This is because ice-clouds usually have larger optical thicknesses and radiative effects than aerosols do, even though ice-clouds generally appear in the upper troposphere where the measurement errors of the SL radiometer-sondes get worse. Actually, the SL radiometer-sondes were used to measure the radiative properties of mid-latitude frontal ice-clouds in the JACCS cirrus experiment (Yoshida et al 2004). …”

“…These sondes were connected in series to a balloon. The combined-sonde observation scheme and the JACCS cirrus experimental results are discussed in a separate paper (Yoshida et al 2004).…”