Abstract
Abstract. The clouds in the Atlantic trade-wind region are known to have an important impact on the global climate system. Acquiring a comprehensive characterization of these clouds based on observations is a challenge, but it is necessary for the evaluation of their representation in models. An exploration of how the macrophysical and microphysical cloud properties and organization of the cloud field impact the large-scale cloud radiative forcing is presented here. In situ measurements of the cloud radiative effects based on the Broadband AirCrAft RaDiometer Instrumentation (BACARDI) on board the High Altitude and LOng Range Research Aircraft (HALO) and cloud observations from the GOES-16 satellite collected during the ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte (EUREC4A) campaign demonstrate what drives the cloud radiative effects in shallow trade-wind clouds. We find that the solar and terrestrial radiative effects of these clouds are largely driven by their macrophysical properties (cloud fraction and a scene-averaged liquid water path). We also conclude that the microphysical properties, cloud top height and organization of the cloud field increasingly determine the cloud radiative effects as the cloud fraction increases.
Highlights
Shallow, marine trade-wind cumuli in the tropics have been established as key components in influencing the radiative energy budget of the Earth’s atmosphere in response to a changing climate (Bony et al, 2017; Klein et al, 2017; Stevens et al, 2021)
When the cloud fractions are in the middle range, the impact of increasing LWPcloud and zct becomes stronger, resulting in higher αce. Both reff and Iorg show a weak positive correlation with αce. This is the first indication from the analyses presented here that the organization of the cloud field, in terms of the degree of clustering, has an impact on the solar radiative effects of the trade-wind cumuli
Bringing together a comprehensive characterization of tradewind clouds based on their macrophysical and microphysical properties and interactions is a challenge, one reason being the lack of representative observational data sets
Summary
Marine trade-wind cumuli in the tropics have been established as key components in influencing the radiative energy budget of the Earth’s atmosphere in response to a changing climate (Bony et al, 2017; Klein et al, 2017; Stevens et al, 2021). The microphysical, macrophysical and radiative properties of these clouds have been mapped out, for example, with the aid of high-resolution satellite observations (Zhao and Di Girolamo, 2007; Mieslinger et al, 2019) and through dedicated research campaigns such as Cloud, Aerosol, Radiation and tuRbulence in the trade regime over Barbados (CARRIBA; Siebert et al, 2013) and the Next-Generation Aircraft Remote Sensing for Validation field studies (NARVAL I and NARVAL II; Stevens et al, 2019). Such observational data sets are ideal for the purposes of process studies and the validation and improvement of numerical weather prediction models (NWPs) and global climate models (GCMs). The impact of shallow trade-wind clouds on the atmospheric radiative energy budget in a warming world remains a critical topic
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