Distributional characteristics and causes of single-layer stratiform clouds in the Southeastern Pacific Ocean

Single-layer stratocumulus 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, creating significant challenges for accurately assessing cloud-climate feedbacks in climate models. In this paper, we use the Cloudsat 2B-CLDCLASS-LIDAR product to distinguish them from other cloud types, and investigate their formation causes and radiative effects with the ERA5 datasets and the 2B-FLXHR-LIDAR. The results show that (1) 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 the effects of TCWV and LTS. (2) the Cloud Fraction (CF) of the single-layer Sc showed an upward trend during January 2007-December 2010. It is believed that the CF interannual variations of the single-layer Sc are related to the monthly temperature and humidity anomalies in the middle and lower layers of the atmospheric troposphere. (3) CF has a larger impact on shortwave radiative forcing than on longwave, but its effect depends on the cloud geometric thickness (CGT). When the cloud layer is thin (61<CGT<941m), the CF enhances the cloud shortwave and longwave radiative forcing, resulting in a regional cooling effect (slope_CERnet=-1.2756); the thick cloud layer (941–1820m) will inhibit both radiation forcings, leading to a warming effect (slope_CERnet=3.0932). These findings will help improve the simulation of cloud radiative forcing, thereby reducing uncertainties in climate change assessments.