Midlatitude mixed-phase stratocumulus clouds and their interactions with aerosols: how ice processes affect microphysical, dynamic, and thermodynamic development in those clouds and interactions?

Seoung Soo Lee,Nobuyuki Utsumi,Go-Un Kim,Byung-Gon Kim,Kyung-Ja Ha,Mohammad Kamruzzaman,Hyungjun Kim,Manguttathil Gopalakrishnan Manoj,Chang Hoon Jung,Youtong Zheng,Jianping Guo,Junshik Um,Kyoung Ock Choi

doi:10.5194/acp-21-16843-2021

Abstract

Abstract. Midlatitude mixed-phase stratocumulus clouds and their interactions with aerosols remain poorly understood. This study examines the roles of ice processes in those clouds and their interactions with aerosols using a large-eddy simulation (LES) framework. Cloud mass becomes much lower in the presence of ice processes and the Wegener–Bergeron–Findeisen (WBF) mechanism in the mixed-phase clouds compared to that in warm clouds. This is because while the WBF mechanism enhances the evaporation of droplets, the low concentration of aerosols acting as ice-nucleating particles (INPs) and cloud ice number concentration (CINC) prevent the efficient deposition of water vapor. Note that the INP concentration in this study is based on the observed spatiotemporal variability of aerosols. This results in the lower CINC compared to that with empirical dependence of the INP concentrations on temperature in a previous study. In the mixed-phase clouds, the increasing concentration of aerosols that act as cloud condensation nuclei (CCN) decreases cloud mass by increasing the evaporation of droplets through the WBF mechanism and decreasing the intensity of updrafts. In contrast to this, in the warm clouds, the absence of the WBF mechanism makes the increase in the evaporation of droplets inefficient, eventually enabling cloud mass to increase with the increasing concentration of aerosols acting as CCN. Here, the results show that when there is an increasing concentration of aerosols that act as INPs, the deposition of water vapor is more efficient than when there is the increasing concentration of aerosols acting as CCN, which in turn enables cloud mass to increase in the mixed-phase clouds.

Highlights

Stratiform clouds such as the stratus and stratocumulus clouds play an important role in global hydrologic and energy circulations (Warren et al, 1986, 1988; Stephens and Greenwald, 1991; Hartmann et al, 1992; Hahn and Warren, 2007; Wood, 2012)
Since in the control-noice run, there are no ice particles, liquid-water path (LWP) acts as water path (WP) in the run
WP is higher in the control-noice run than in the control run throughout the whole simulation period

Summary

Introduction

Stratiform clouds such as the stratus and stratocumulus clouds play an important role in global hydrologic and energy circulations (Warren et al, 1986, 1988; Stephens and Greenwald, 1991; Hartmann et al, 1992; Hahn and Warren, 2007; Wood, 2012). Increasing aerosols may suppress precipitation and, alter the mass and lifetime of those clouds (Albrecht, 1989; Guo et al, 2016) These aerosol effects strongly depend on how increasing aerosols affect entrainment at the tops of the planetary boundary layer (PBL) (Ackerman et al, 2004) and disrupt global hydrologic and energy circulations. Same as in the INP- Absent reduced run Present Absent Present Present Present Present uary when WP reaches its maximum value in each of the runs (Fig. 5a) These differences decrease as time goes by after around 00:00 LST on 13 January (Fig. 5a).

Objectives

Results

Conclusion