Linking Atmospheric Cloud Radiative Effects and Tropical Precipitation

Needham, Michael Robert; Randall, David A.

doi:10.1029/2021gl094004

Cited by 4 publications

(7 citation statements)

References 49 publications

(96 reference statements)

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“…Section 2 provides an overview of the simulations used in this study, and includes a discussion of our analysis methods. In section 3 we show that the ACRE is large in humid regions, consistent with the main conclusions of Needham and Randall (2021).…”

Section: Accepted Articlesupporting

confidence: 84%

“…Section 2 provides an overview of the simulations used in this study, and includes a discussion of our analysis methods. In Section 3, we show that the ACRE becomes large in humid regions, consistent with the main conclusions of Needham and Randall (2021). The moisture and energy budgets are analyzed in NEEDHAM AND RANDALL 10.1029/2021JD035019 2 of 21 Section 4, and the vertical structure is investigated in Section 5.…”

Section: Introductionsupporting

confidence: 66%

“…In a recent paper, Needham and Randall (2021) demonstrated a nonlinear relationship between the mean ACRE and the CRH that is similar to the aforementioned relationship between precipitation and CRH. They also suggested that the ACRE favors the exponential relationship between precipitation and CRH because it facilitates a shift from convective-scale to stratiform ascent (Ahmed & Schumacher, 2015;Jenney et al, 2020).…”

Section: Introductionmentioning

confidence: 54%

“…A key conclusion of Needham and Randall (2021) was that the mean ACRE for a particular CRH was nearly identical in different regions of the tropics. The same conclusion is reached here in the context of these idealized simulations: as the SST increases, the ACRE at a given CRH appears to be nearly unchanged.…”

Section: Cre Versus Crhmentioning

confidence: 99%

“…Model diagnostics are analyzed by taking the area weighted average value of a field using only those grid cells with CRH within a bin of width 2%, and then repeating for all bins between 0% and 100% CRH. Similar analyses using the CRH have been used previously (e.g., Bretherton et al (2005); Wing and Emanuel (2014); Jenney et al (2020)), and the method used here is identical to that of Needham and Randall (2021). -7-…”

Section: Analysis Using the Column Relative Humiditymentioning

confidence: 99%

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Riehl and Malkus Revisited: The Role of Cloud Radiative Effects

Needham

Randall

2021

JGR Atmospheres

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The intertropical convergence zone (ITCZ) exports energy and imports moisture. This has been understood for decades. By analyzing a set of uniform, nonrotating aquaplanet simulations, we show that energy export and moisture convergence are general characteristics of warm humid regions, and not just of the ITCZ. Using an analysis method based on the column relative humidity, we find that the absorption of longwave radiation by clouds supplies the energy that is exported from humid regions. The longwave absorption also induces a thermally direct circulation that lifts water vapor and converges moisture into regions that are already quite humid. An additional set of simulations shows that strong atmospheric energy convergence is absent when radiation is homogenized across the domain.

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Section: Accepted Articlesupporting

confidence: 84%

Section: Introductionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 54%

Section: Cre Versus Crhmentioning

confidence: 99%

Section: Analysis Using the Column Relative Humiditymentioning

confidence: 99%

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Riehl and Malkus Revisited: The Role of Cloud Radiative Effects

Needham

Randall

2021

JGR Atmospheres

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Tropical Deep Convection, Cloud Feedbacks and Climate Sensitivity

Stephens,

Shiro,

Hakuba

et al. 2024

Surv Geophys

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This paper is concerned with how the diabatically-forced overturning circulations of the atmosphere, established by the deep convection within the tropical trough zone (TTZ), first introduced by Riehl and (Malkus) Simpson, in Contr Atmos Phys 52:287–305 (1979), fundamentally shape the distributions of tropical and subtropical cloudiness and the changes to cloudiness as Earth warms. The study first draws on an analysis of a range of observations to understand the connections between the energetics of the TTZ, convection and clouds. These observations reveal a tight coupling of the two main components of the diabatic heating, the cloud component of radiative heating, shaped mostly by high clouds formed by deep convection, and the latent heating associated with the precipitation. Interannual variability of the TTZ reveals a marked variation that connects the depth of the tropical troposphere, the depth of convection, the thickness of high clouds and the TOA radiative imbalance. The study examines connections between this convective zone and cloud changes further afield in the context of CMIP6 model experiments of climate warming. The warming realized in the CMIP6 SSP5-8.5 scenario multi-model experiments, for example, produces an enhanced Hadley circulation with increased heating in the zone of tropical deep convection and increased radiative cooling and subsidence in the subtropical regions. This impacts low cloud changes and in turn the model warming response through low cloud feedbacks. The pattern of warming produced by models, also influenced by convection in the tropical region, has a profound influence on the projected global warming.

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Understanding the Mechanisms for Tropical Surface Impacts of the Quasi‐Biennial Oscillation (QBO)

García‐Franco,

Gray,

Osprey

et al. 2023

JGR Atmospheres

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The impact of the quasi‐biennial oscillation (QBO) on tropical convection and precipitation is investigated through nudging experiments using the UK Met Office Hadley Center Unified Model. The model control simulations show robust links between the internally generated QBO and tropical precipitation and circulation. The model zonal wind in the tropical stratosphere was nudged above 90 hPa in atmosphere‐only and coupled ocean‐atmosphere configurations. The convection and precipitation in the atmosphere‐only simulations do not differ between the experiments with and without nudging, which may indicate that SST‐convection coupling is needed for any QBO influence on the tropical lower troposphere and surface. In the coupled experiments, the precipitation and sea‐surface temperature relationships with the QBO phase disappear when nudging is applied. Imposing a realistic QBO‐driven static stability anomaly in the upper‐troposphere lower‐stratosphere is not sufficient to simulate tropical surface impacts. The nudging reduced the influence of the lower troposphere on the upper branch of the Walker circulation, irrespective of the QBO, indicating that the upper tropospheric zonal circulation has been decoupled from the surface by the nudging. These results suggest that grid‐point nudging mutes relevant feedback processes occurring at the tropopause level, including high cloud radiative effects and wave mean flow interactions, which may play a key role in stratospheric‐tropospheric coupling.

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Linking Atmospheric Cloud Radiative Effects and Tropical Precipitation

Cited by 4 publications

References 49 publications

Riehl and Malkus Revisited: The Role of Cloud Radiative Effects

Riehl and Malkus Revisited: The Role of Cloud Radiative Effects

Tropical Deep Convection, Cloud Feedbacks and Climate Sensitivity

Understanding the Mechanisms for Tropical Surface Impacts of the Quasi‐Biennial Oscillation (QBO)

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