Investigating the impact of cloud-radiative feedbacks on tropical precipitation extremes

Abstract

Although societally important, extreme precipitation is difficult to represent in climate models. This study shows one robust aspect of extreme precipitation across models: extreme precipitation over tropical oceans is strengthened through a positive feedback with cloud-radiative effects. This connection is shown for a multi-model ensemble with experiments that make clouds transparent to longwave radiation. In all cases, tropical extreme precipitation reduces without cloud-radiative effects. Qualitatively similar results are presented for one model using the cloud-locking method to remove cloud feedbacks. The reduced extreme precipitation without cloud-radiative feedbacks does not arise from changes in the mean climate. Rather, evidence is presented that cloud-radiative feedbacks enhance organization of convection and most extreme precipitation over tropical oceans occurs within organized systems. This result suggests that climate models must correctly predict cloud structure and properties, as well as capture the essence of organized convection in order to accurately represent extreme rainfall.

Riehl and Malkus Revisited: The Role of Cloud Radiative Effects

“…They found that removing the ACRE above 600 hPa led to a reduction in the strength of the Hadley and Walker circulations. Similar results have been obtained in more recent studies utilizing updated GCMs, which have also noted the role of ACRE in determining the width of the ITCZ, reducing the double‐ITCZ bias, and strengthening the precipitation associated with various tropical phenomena (Albern et al., 2018; Benedict et al., 2020; Harrop & Hartmann, 2016; Li et al., 2015; Medeiros et al., 2021; Popp & Silvers, 2017; Voigt & Albern, 2019). For a recent review of the interactions between clouds, radiation, and atmospheric circulations, see Voigt et al.…”

“…Recently, Benedict et al (2020) used a set of mechanism-denial experiments to show that removing the ACRE weakens the MJO. Medeiros et al (2021) also found that removing cloud radiative feedbacks weakens tropical precipitation by reducing the frequency of extreme precipitation events. Ruppert et al (2020) have shown that a similar feedback promotes the intensification of tropical cyclones.…”

“…Medeiros et al. (2021) also found that removing cloud radiative feedbacks weakens tropical precipitation by reducing the frequency of extreme precipitation events. Ruppert et al.…”

Linking Atmospheric Cloud Radiative Effects and Tropical Precipitation

“…The longwave ACRE has been identified as an important feedback mechanism in the context of the persistence of convective self‐aggregation, the initial development of tropical cyclones, and the Madden‐Julian Oscillation (Arnold & Randall, 2015; Benedict et al., 2020; Bretherton et al., 2005; Chikira, 2014; Emanuel, 2019; Khairoutdinov & Emanuel, 2018; Medeiros et al., 2021; Ruppert et al., 2020; Wing et al., 2017; Wolding et al., 2016). The longwave ACRE can be a strong localized atmospheric heating that induces a thermally direct circulation connecting humid and dry regions.…”

Investigating the Causes and Impacts of Convective Aggregation in a High Resolution Atmospheric GCM

“…However, Li et al (2015) found that CRE can decrease precipitation in the tropics but increase it at middle-to-high latitudes. Recently, Medeiros et al (2021) reported that extreme precipitation over tropical ocean is strengthened by CRE. While mean precipitation and large-scale circulation can be affected by removing CRE, it is unclear how precipitation, especially extreme precipitation, will respond if radiative-convective interactions are disabled.…”