Abstract
Abstract. The representations of clouds, aerosols, and cloud–aerosol–radiation impacts remain some of the largest uncertainties in climate change, limiting our ability to accurately reconstruct past climate and predict future climate. The south-east Atlantic is a region where high atmospheric aerosol loadings and semi-permanent stratocumulus clouds are co-located, providing an optimum region for studying the full range of aerosol–radiation and aerosol–cloud interactions and their perturbations of the Earth's radiation budget. While satellite measurements have provided some useful insights into aerosol–radiation and aerosol–cloud interactions over the region, these observations do not have the spatial and temporal resolution, nor the required level of precision to allow for a process-level assessment. Detailed measurements from high spatial and temporal resolution airborne atmospheric measurements in the region are very sparse, limiting their use in assessing the performance of aerosol modelling in numerical weather prediction and climate models. CLARIFY-2017 was a major consortium programme consisting of five principal UK universities with project partners from the UK Met Office and European- and USA-based universities and research centres involved in the complementary ORACLES, LASIC, and AEROCLO-sA projects. The aims of CLARIFY-2017 were fourfold: (1) to improve the representation and reduce uncertainty in model estimates of the direct, semi-direct, and indirect radiative effect of absorbing biomass burning aerosols; (2) to improve our knowledge and representation of the processes determining stratocumulus cloud microphysical and radiative properties and their transition to cumulus regimes; (3) to challenge, validate, and improve satellite retrievals of cloud and aerosol properties and their radiative impacts; (4) to improve the impacts of aerosols in weather and climate numerical models. This paper describes the modelling and measurement strategies central to the CLARIFY-2017 deployment of the FAAM BAe146 instrumented aircraft campaign, summarizes the flight objectives and flight patterns, and highlights some key results from our initial analyses.
Highlights
Introduction and rationaleThe interactions of clouds, aerosols, and radiation are highlighted as key climate uncertainties in the most recent Intergovernmental Panel on Climate Change (IPCC) assessment report (Boucher et al, 2013)
This overview paper documents the planning, logistics, aircraft capabilities, measurement strategies, manoeuvres, and observations made under the CLARIFY-2017 deployment of the FAAM aircraft, together with complementary numerical weather prediction (NWP) and climate modelling studies
– Biomass burning aerosol size distributions derived from measurements in the residual continental boundary layer (CBL) were found to closely resemble the more limited measurements performed during SAFARI-2000, a one-mode or two-mode model (Peers et al, 2019, 2020; Taylor et al, 2020; Wu et al, 2021) might be preferred, owing to its relative simplicity when utilized in satellite retrieval algorithms
Summary
The interactions of clouds, aerosols, and radiation are highlighted as key climate uncertainties in the most recent Intergovernmental Panel on Climate Change (IPCC) assessment report (Boucher et al, 2013). – AEROCLO-sA (AErosol, RadiatiOn and CLOuds in southern Africa), which deployed a surface mobile platform and the instrumented French Falcon 20 environmental research aircraft of Safire in Henties Bay and Walvis Bay, respectively, in 2017 (Formenti et al, 2019) All of these measurement campaigns comprised major deployments of research assets to the South Atlantic region during 2017 (Zuidema et al, 2016). de Graaf et al (2012) used high spectral resolution satellite data to show that the direct radiative effect of BBA over clouds in the SE Atlantic region could be stronger than +130 W m−2 instantaneously and +23 W m−2 in the monthly mean These values are far stronger than those diagnosed in climate models which reach only +50 W m−2 instantaneously Atlantic sea-surface temperature gradients and the hemispherical asymmetry in the energy balance are strongly impacted by SE Atlantic stratocumulus (Jones and Haywood, 2012; Stephens et al, 2016), influencing the position of the intertropical convergence zone (ITCZ) and the African and Asian monsoon
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