Distributional characteristics and causes of single-layer stratiform clouds over typical region in the southeastern Pacific Ocean

Abstract

Single-layer Stratiform clouds (Sc), as the most common cloud system for stratiform clouds, plays an important role in global radiative balance due to their duration and extensive coverage. However, there are still substantial uncertainties in their formation and radiative forcing. In this paper, we use the Cloudsat 2B-CLDCLASS-LIDAR product from 2007 to 2010 to distinguish it from other cloud types. ERA5 data and 2B-FLXHR-LIDAR from the same period are used to investigate its formation mechanisms and radiative effects. The results show that the single-layer Sc exhibits obvious seasonal variation in the spatial distribution, which is closely related to the distribution of whole-layer humidity (TCWV) and Lower Tropospheric Stability (LTS). Different aerosol concentrations alter their effects. When aerosol optical depth (AOD) is less than 0.12, increased TCWV suppresses cloud formation, amplified by stronger LTS. However, as AOD > 0.14, TCWV promotes cloud fraction (CF), while LTS weakens this effect. CGT is a key meteorological indicator that, when fixed, reduces the impact of meteorological factors (e.g., TCWV, LTS) on cloud structure, enabling a clearer assessment of CF' s effect on cloud radiative effect (CRE). The results show CF has a larger impact on shortwave radiative forcing (CRE_SW) than on longwave (CRE_SW), but its effect depends on the cloud geometric thickness (CGT). When the cloud layer is thin (CGT < 310.3 m), the CF enhances the cloud shortwave and longwave radiative effect, resulting in a regional cooling effect (slope_{_CERnet} = −25.2); the thick cloud layer (CGT > 310.3 m) will inhibit CRE_SW but enhance CRE_LW, thereby diminishing the cooling effect (slope_{_CERnet} = −19.89). This study will help improve the simulation of cloud radiative forcing, thereby reducing uncertainties in climate change assessments.