A Relationship Between ITCZ Organization and Subtropical Humidity

Hohenegger, Cathy; Jakob, Christian

doi:10.1029/2020gl088515

Cited by 8 publications

(5 citation statements)

References 28 publications

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“…Khairoutdinov & Emanuel (2010) first discovered that the degree of convective aggregation could affect climate sensitivity because of its strong impact on top-of-atmosphere radiation balance. It was shown that self-aggregation is associated with a drying of the atmosphere in both simulations (Bretherton et al 2005) and observations (Hohenegger & Jakob 2020). This drying allows more outgoing long-wave radiation to space, cooling the planet.…”

Section: Climate Sensitivitymentioning

confidence: 87%

Spontaneous Aggregation of Convective Storms

Muller

Yang

Craig

et al. 2022

Annu. Rev. Fluid Mech.

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Idealized simulations of the tropical atmosphere have predicted that clouds can spontaneously clump together in space, despite perfectly homogeneous settings. This phenomenon has been called self-aggregation, and it results in a state where a moist cloudy region with intense deep convective storms is surrounded by extremely dry subsiding air devoid of deep clouds. We review here the main findings from theoretical work and idealized models of this phenomenon, highlighting the physical processes believed to play a key role in convective self-aggregation. We also review the growing literature on the importance and implications of this phenomenon for the tropical atmosphere, notably, for the hydrological cycle and for precipitation extremes, in our current and in a warming climate. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Section: Climate Sensitivitymentioning

confidence: 87%

Spontaneous Aggregation of Convective Storms

Muller

Yang

Craig

et al. 2022

Annu. Rev. Fluid Mech.

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“…In addition to spontaneously self‐aggregating, convection can also be “forced” to aggregate by an SST gradient (Hohenegger & Jakob, 2020; Lutsko & Cronin, 2023; Müller & Hohenegger, 2020). In idealized “mock Walker” simulations, a simple SST gradient is imposed, forcing a large‐scale overturning circulation (Bretherton et al., 2006; Grabowski et al., 2000; Lutsko & Cronin, 2023).…”

Section: Introductionmentioning

confidence: 99%

Convection and Convective‐Organization in Hothouse Climates

Dagan,

Seeley,

Steiger

2023

J Adv Model Earth Syst

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In a “hothouse” climate, warm temperatures lead to a high tropospheric water vapor concentration. Sufficiently high water vapor levels lead to the closing of the water vapor infrared window, which prevents radiative cooling of the lower troposphere. Because water vapor also weakly absorbs solar radiation, hothouse climates feature radiative heating of the lower troposphere. In recent work, this radiative heating was shown to trigger a shift into a novel “episodic deluge” precipitation regime, where rainfall occurs in short, intense outbursts separated by multi‐day dry spells. Here, we further examine the role of the lower tropospheric radiative heating (LTRH) in the transition into the “episodic deluge” regime. We demonstrate that under high sea‐surface temperature the “episodic deluge” regime could be formed even before the LTRH turns positive. In addition, we examine whether these oscillations operate on larger scales and how these oscillations, which represent “temporal” convective self‐organization, would manifest in the presence of traditional “spatial” self‐ or forced‐aggregation in large‐domain convection‐permitting simulations. We find that the temporal oscillations become much less synchronized throughout a large domain ( 1,000 km) because gravity waves cannot propagate fast enough to synchronize convection. We also show that temporal oscillations still dominate the rainfall distribution even when there is tropical convective self‐aggregation or a large‐scale overturning circulation. These results could have important implications for extreme precipitation events under a warming climate.

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“…To summarize, while the structure of low‐level convergence has been discussed in a few studies, there is still no clear consensus on how best to describe it. Theoretical and modeling studies usually emphasize a single convergence line (see e.g., Hohenegger & Jakob, 2020, for a recent example), whereby observations tend to document a more complex structure, often better idealized as a double convergence line, as shown schematically in Figure 1a and b respectively. To the extent that convergence within the ITCZ is associated with several lines of convergence that extend only a few degrees of longitude (Weller et al ., 2017), our limiting cases in Figure 1 encapsulate the idea that these lines tend to form and dissipate in the center, or toward the edges, of the rain belt.…”

Section: Introductionmentioning

confidence: 99%

The inner life of the Atlantic Intertropical Convergence Zone

Windmiller,

Stevens

2023

Quart J Royal Meteoro Soc

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The intertropical convergence zone (ITCZ) is a central component of the atmospheric general circulation, but remarkably little is known about the dynamical and thermodynamical structure of the convergence zone itself. This is true even for the structure of the low‐level convergence that gives the ITCZ its name. Following on from the major international field campaigns in the 1960s and 70s, we performed extensive atmospheric profiling of the Atlantic ITCZ during a ship‐based measurement campaign aboard the research vessel SONNE in summer 2021. Combining data collected during our north‐south crossing of the ITCZ with reanalysis data shows the ITCZ to be a meridionally extended region of intense precipitation, with enhanced surface convergence at its edges rather than in the center. Based on the location of these edges, we construct a composite view of the structure of the Atlantic ITCZ. The ITCZ, far from being simply a region of enhanced deep convection, has a rich inner life, i.e., a rich dynamical and thermodynamic structure that changes throughout the course of the year and has a northern edge that differs systematically from the southern edge.This article is protected by copyright. All rights reserved.

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A Relationship Between ITCZ Organization and Subtropical Humidity

Cited by 8 publications

References 28 publications

Spontaneous Aggregation of Convective Storms

Spontaneous Aggregation of Convective Storms

Convection and Convective‐Organization in Hothouse Climates

The inner life of the Atlantic Intertropical Convergence Zone

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