Satellite–Based Insights into Precipitation Formation Processes in Continental and Maritime Convective Clouds

Abstract

Multispectral analyses of satellite images are used to calculate the evolution of the effective radius of convective cloud particles with temperature, and to infer from that information about precipitation forming processes in the clouds. Different microphysical processes are identified at different heights. From cloud base to top, the microphysical classification includes zones of diffusional droplet growth, coalescence droplet growth, rainout, mixed-phase precipitation, and glaciation. Not all zones need appear in a given cloud system. Application to maritime clouds shows, from base to top, zones of coalescence, rainout, a shallow mixed-phase region, and glaciation starting at -10°C or even warmer. In contrast, continental clouds have a deep diffusional growth zone above their bases, followed by coalescence and mixedphase zones, and glaciation at -15° to -20°C. Highly continental clouds have a narrow or no coalescence zone, a deep mixed-phase zone, and glaciation occurring between -20° and -30°C. Limited aircraft validation for the satellite inferences over Israel, Thailand, and Indonesia is available.Substantial transformation in the microphysical and precipitation forming processes is observed by this method in convective clouds developing in air masses moving from the sea inland. These changes appear to be related to the modification of the maritime air mass as it moves inland and becomes more continental. Further transformations are observed in air masses moving into areas affected by biomass burning smoke or urban air pollution, such that coalescence, and thus precipitation, is suppressed even in deep tropical clouds. It follows that natural and anthropogenic aerosols can substantially modify clouds not only in pristine environments, as was already demonstrated by the ship tracks, but they can also incur profound impact on cloud microstructure and precipitation in more continental environments, leading to substantial weather modification in densely populated areas.

TRMM observed first direct evidence of smoke from forest fires inhibiting rainfall

“…Effective radius is the cloud droplet size distribution parameter, which is observable by satellites. It has already been observed by satellite that re decreased below the precipitation threshold of re=14 gtm in clouds infected by smoke from burning vegetation in the Amazon [Kaufman and Fraser, 1997] and Indonesia [RosenfeM and Lensky, 1998]. However, these studies did not provide direct evidence showing how the smoke actually suppresses precipitation, such as presented in the current study.…”

Smoking Rain Clouds over the Amazon

“…5). This leads to profound differences in the precipitation processes, along the lines inferred by satellite observations (6,7,20). The shift of onset of precipitation to large H under smoky conditions leads to formation of large ice hydrometeors that were reported on the ground as large hail (up to 2 cm) and also produced small dents on the aircraft nose cone after flying in smoky conditions at cloud base level on 23 September 2002.…”

“…4C), at least up to the aircraft operational height limitation of 4.5 km. Satellite retrievals of cloud top particle effective radius (20) suggested that the precipitation threshold of 14 m was exceeded at -22°C and -28°C, which correspond to H of 6600 and 7600 m for the smoky and pyro-clouds, respectively (Fig. 5).…”

An integrated approach toward the incorporation of clouds in the temperature retrievals from microwave measurements

“…In the radiative transfer calculations we use the model of Rosenkranz and the model of Liebe for the absorption coefficient calculations: Rosenkranz (1998) for H 2 O, Rosenkranz (1993) for O 2 and Liebe et al (1993) for N 2 (Stähli et al, 2013). A tropospheric water vapour profile with an exponential decrease is included.…”

“…This parameter indicates the mass of liquid water per unit volume of air and is usually expressed in g m −3 . Different authors have characterized the LWC for different kinds of clouds (Hess et al, 1998;Korolev et al, 2007;Rosenfeld and Lensky, 1998). Cirrus and fog present much lower water content than other kinds of clouds, with values around 0.03 and 0.06 g m −3 , respectively.…”