WCD-24. Understanding the impact of natural meteorological co-variability on the radiative responses of shallow marine clouds from diurnal to decadal timescales

Quantifying the radiative effects of shallow marine clouds is challenging and is one of the greatest sources of uncertainty for climate projection. A major difficulty emanates from identifying the relationship between ever-changing meteorological conditions and cloud radiative properties, and how this relationship links to regional cloud radiative effects over long timescales. The uncertainty is exacerbated by cloud-aerosol interactions associated with the advection of anthropogenic aerosols at different timescales. To build more confidence in the projections of climate change, it is imperative that we make progress on a quantitative understanding of cloud radiative responses to co-varying meteorological and aerosol conditions across timescales. In this study, we apply continuous wavelet transforms to 40 years of hourly cloud properties and meteorological data from the fifth generation ECMWF reanalysis (ERA5) over the Eastern North/South Atlantic and North/South East Pacific to quantify their characteristic frequencies. We perform wavelet coherence analysis to evaluate, from diurnal to decadal timescales, the natural co-variability between cloud controlling factors (CCFs) associated with meteorological conditions and the corresponding radiative responses of shallow warm clouds. Aerosol, sourced from the Copernicus Atmosphere Monitoring Service (CAMS), is considered an important CCF because it can significantly change cloud properties. This study provides a foundation for our follow-on numerical study where we quantify the relationship between co-varying meteorology and aerosol perturbations, and the strength of the radiative effect.