The nature of ice-nucleating particles affects the radiative properties of tropical convective cloud systems

Abstract

<jats:p>Abstract. Convective cloud systems in the maritime tropics play a critical role in global climate, but accurately representing aerosol interactions within these clouds persists as a major challenge for weather and climate modelling. We quantify the effect of ice-nucleating particles (INP) on the radiative properties of a complex Tropical Atlantic deep convective cloud field using a regional model with an advanced double-moment microphysics scheme. Our results show that the domain-mean daylight outgoing radiation varies by up to 18 W m−2 depending on the bio- and physico-chemical properties of INP. The key distinction between different INPs is the temperature dependence of ice formation, which alters the vertical distribution of cloud microphysical processes. The controlling effect of the INP temperature dependence is substantial even in the presence of secondary ice production, and the effects of secondary ice formation depend strongly on the nature of the INP. Our results have implications for climate model simulations of tropical clouds and radiation, which currently do not consider a link between INP particle type and ice water content. The results also provide a challenge to the INP measurement community, since we demonstrate that INP concentration measurements are required over the full mixed-phase temperature regime, which covers around 10 orders of magnitude in INP concentration. </jats:p>

Sensitivity of mixed-phase moderately deep convective clouds to parameterizations of ice formation – an ensemble perspective

“…As forecasts of convective situations often have a low intrinsic predictability (e.g. Hohenegger and Schär, 2007), it is particularly interesting to use ensemble simulations with perturbed initial conditions as context for sensitivity experiments regarding the model formulation. Here, we use high-resolution ensemble simulations for the COPE case, which were already used by Miltenberger et al (2018b) to provide context for sensitivity experiments regarding the background aerosol concentration.…”

“…The latter is particularly important for convective situations with a small intrinsic predictability, as any small perturbation may rapidly amplify under these conditions (e.g. Hohenegger and Schär, 2007;Dey et al, 2014). The relevance of taking the predictability of different situations into account when assessing the sensitivity to parameterization changes is gaining increasing attention (e.g.…”

Mineral and biological ice-nucleating particles above the South East of the British Isles

“…Climate models tend to oversimplify and poorly represent the ice-related processes such as ice formation triggered by the presence of INPs. INPs and ice production are important in deep convective clouds, 4,5 as well as shallow clouds, 3 but it is becoming increasingly clear that the representation of iceprocesses is particularly important in dening the amount of water and ice that models produce in shallow clouds. [6][7][8] This difficulty in properly representing the amount of supercooled water in shallow mid-and high-latitude mixed-phase clouds is a key cause of the large uncertainty in the negative cloud-phase feedback.…”

Understanding size-resolved dust emission from field measurements in Morocco

“…Dust, acting as cloud condensation nuclei (CCN) and ice nucleating particles (INPs), indirectly affects the Earth's energy balance by influencing cloud microphysical properties (DeMott et al, 2003;Atkinson et al, 2013;Hawker et al, 2021).…”

“…Dust is also a prominent source of INPs, exerting considerable influence on cold cloud processes all around the planet from the surface to the top of the troposphere (Murray et al, 2012;Vergara-Temprado et al, 2017;Froyd et al, 2022). The activation of INPs is influenced by various factors, including the properties of dust such as its composition, size, and surface defects, as well as environmental factors such as particle concentration, temperature and humidity (Möhler et al, 2006;Yakobi-Hancock et al, 2013;Takeishi and Storelvmo, 2018;Hawker et al, 2021). Recent modelling studies have analyzed the impact of INPs on convective clouds (Takeishi and Storelvmo, 2018;Hawker et al, 2021).…”