Comment on acp-2022-731

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> To better measure the planetary boundary layer inversion strength (IS), a novel profile-based estimated inversion strength (EISp) is developed using the ERA5 daily reanalysis data. The EISp is designed to estimate the IS based on the thinnest possible reanalysis layer above the lifting condensation level encompassing the inversion layer. At the Southern Great Plains site, the EISp better correlates with the radiosonde-detected IS (R=0.74) than the lower-tropospheric stability (LTS, R=0.53) and the estimated inversion strength (EIS, R=0.45). And the daily variance in low-cloud cover (LCC) explained by the EISp is twice that explained by the LTS and EIS. Higher correlations between the EISp and the radiosonde-detected IS are also found at worldwide radiosonde stations. Analysis on LCC observed by geostationary satellites and the Moderate Resolution Imaging Spectroradiometer shows that the EISp explains 78&thinsp;% of the annual mean LCC spatial variance over global oceans and land, larger than that explained by the LTS / EIS (48&thinsp;% / 13&thinsp;%). Over tropical and subtropical low-cloud prevailing eastern oceans, LCC range is more resolved by the EISp (48&thinsp;%) than the LTS / EIS (37&thinsp;% / 36&thinsp;%). And the EISp explains a larger fraction (32&thinsp;%) in the daily LCC variance, as compared to that explained by the LTS / EIS (14&thinsp;% / 16&thinsp;%). The seasonal LCC variance explained by the EISp is 89&thinsp;%, larger than that explained by the LTS/EIS (80&thinsp;% / 70&thinsp;%). The relationship between EISp and LCC is more uniform across various time scales than the LCC-LTS / EIS relationship. It is suggested that the EISp is a better cloud controlling factor for LCC and likely a useful external environmental constraint for process-level studies in which there is a need to control for large-scale meteorology in order to isolate the cloud responses to aerosols on short timescales.