The characteristics of African easterly waves coupled to Saharan mineral dust aerosols

Grogan, D.; Thorncroft, C. D.

doi:10.1002/qj.3483

Cited by 24 publications

(35 citation statements)

References 74 publications

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“…The meridion / 0 y γ ∂ ∂ > ), whereas the transports ar both latitude belts, the meridional du (see Figure 4b). This agrees with the Grogan and Thorncroft [33]. The eq magnitude larger than the poleward critical surface.…”

Section: Wrf-dust Modelsupporting

confidence: 90%

“…Thus within both latitude belts, the meridional dust transports are directed down the background dust gradient (see Figure 4b). This agrees with the statistical analyses of the dust-coupled AEWs carried out by Grogan and Thorncroft [33]. The equatorward transports, which are as much as three orders of magnitude larger than the poleward transports, are maximized at~18 • N,~775 hPa, i.e., near the critical surface.…”

Section: Wrf-dust Modelsupporting

confidence: 90%

“…The equatorward transports, which are as much as three orders of magnitude larger than the poleward transports, are maximized at~18 • N,~775 hPa, i.e., near the critical surface. The latitude of maximum meridional transports also agrees with Grogan and Thorncroft [33]. The vertical dust transports are upward both north and south of the dust maximum, and, like the meridional transports, are down the background dust gradient and are largest at~18 • N,~775 hPa.…”

Section: Wrf-dust Modelsupporting

confidence: 83%

“…The eq magnitude larger than the poleward critical surface. The latitude of ma Thorncroft [33]. The vertical dust tran and, like the meridional transports, a N, ~775 hPa.…”

Section: Wrf-dust Modelmentioning

confidence: 99%

“…Jones et al [30] did not, however, identify how the structure, growth, and propagation of the AEWs controlled the dust transport. Grogan and Thorncroft [33] examined the three-dimensional structure of dust-coupled AEWs using the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2). Using the MERRA-2 heating rates to compute the diabatic generation of eddy APE, they found that the correlation between the heating rates and the dust anomalies was consistent with the dust-induced generation of APE at mid-levels north of the AEJ axis, which is in agreement with idealized analytical studies of Grogan et al [26] and Nathan et al [28].…”

Section: Governing Equationsmentioning

confidence: 99%

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Saharan Dust Transport during the Incipient Growth Phase of African Easterly Waves

2019

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An analytical analysis is combined with numerical modeling simulations in order to expose the physical and dynamical processes that control the zonal-mean transport of Saharan mineral dust aerosols during the incipient growth phase of African easterly waves. The analytical analysis provides the theoretical basis for understanding and predicting how the waves and background flow combine to affect the zonal-mean eddy transports of dust. The analytically derived transport equations―which are valid for any wave field, irrespective of its spatial or temporal scale―predict that the eddy transports of dust are largest where the maximum in the background dust gradients coincide with a critical surface, i.e., where the Doppler-shifted frequency of the wave field vanishes. Linear simulations of the eddy dust transports are conducted using a mechanistic version of the Weather Research and Forecasting (WRF) model coupled to an interactive dust model. The simulations show that the eddy dust transports are directed down the background dust gradients and that the meridional transports of dust dominate over the vertical transports. The numerical simulations confirm the theoretical predictions. The predictions are used to explain recent statistical analyses of reanalysis data for dust-coupled African easterly waves.

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Section: Wrf-dust Modelsupporting

confidence: 90%

Section: Wrf-dust Modelsupporting

confidence: 90%

Section: Wrf-dust Modelsupporting

confidence: 83%

“…The eq magnitude larger than the poleward critical surface. The latitude of ma Thorncroft [33]. The vertical dust tran and, like the meridional transports, a N, ~775 hPa.…”

Section: Wrf-dust Modelmentioning

confidence: 99%

Section: Governing Equationsmentioning

confidence: 99%

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Saharan Dust Transport during the Incipient Growth Phase of African Easterly Waves

2019

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Formation of a low‐level barrier jet and its modulation by dust radiative forcing over the Hexi Corridor in Central China on March 17, 2010

Chen

McDowell

Huang

et al. 2021

Quart J Royal Meteoro Soc

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A low-level barrier jet (LLBJ) formed along the northeast slope of the Tibetan Plateau on March 17, 2010. The LLBJ was accompanied by a major dust event. Numerical simulations conducted with the Weather Research and Forecasting dust (WRF-dust) model show that the formation of the LLBJ was primarily due to mid-level, southeastward descent of high momentum air, which impinged on the north slope of the Tibetan Plateau, resulting in ageostrophic flow acceleration under geostrophic adjustment. The LLBJ was reinforced by the Bernoulli effect, where the physical barrier associated with the Tibetan Plateau to the southwest and the virtual barrier associated with sloped, packed isentropic surfaces to the northeast combined to constrict the air flow, thus augmenting the acceleration of the air as it entered the Hexi Corridor. The simulations show that the LLBJ, which stayed close to the western entrance of the Hexi Corridor, gradually descended during the daytime until early evening. During this period, the core of the LLBJ stayed directly above the 302-K isentropic surface. The LLBJ, which was located to the south of the main dust plume, was modulated by dust radiative heating and cooling. Over the main dust plume, as well as in the LLBJ region, radiative heating of the dust warmed the upper part of the boundary layer and cooled it below, which stabilized the boundary layer, decreased the boundary layer depth, and reduced the vertical mixing, causing the surface winds to weaken. As a consequence of the feedback between the circulation and the dust radiative forcing, the total dust emission was reduced by ∼9.7-11% and peaked 1-2 hr earlier than without dust radiative effects, while the LLBJ's intensity, which was 1-2 m⋅s −1 stronger, was better maintained within the boundary layer during the daytime until early evening.

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Dynamical study of three African Easterly Waves in September 2021

Jonville,

Flamant,

Lavaysse

2024

Quart J Royal Meteoro Soc

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Three convectively active African easterly waves (AEWs) that propagated south of the African easterly jet were observed over the northeast Atlantic Ocean in September 2021. Their evolution is studied using a suite of theoretical frameworks, as well as the European Centre for Medium‐range Weather Forecast reanalyses and satellite‐derived brightness temperature observations. The environment of these AEWs was sampled during the Cloud–Atmospheric Dynamics–Dust Interactions in West Africa campaign near Cape Verde with the goal to assess their potential for developing into tropical cyclones. We highlight the processes that inhibited the development of the first AEW (which evolved into tropical disturbance Pierre‐Henri) and that played a role in the development of the later two into tropical storms Rose and Peter on September 19, 2021. The three AEWs developed a so‐called “marsupial protective” pouch. For Peter and Rose, the pouch was associated with a vertically aligned vortex at low levels and efficiently protected the convective systems inside from dry and dusty air intrusion. The development of this low‐level vortex is associated with an interaction with the monsoon trough for Rose and with a vorticity center associated with a wave propagating north of the African easterly jet (AEJ) in the case of Peter. The presence of a dust flux toward the convective core near the surface is highlighted for Rose and Peter in spite of the presence of the protective marsupial pouch. On the other hand, Pierre‐Henri interacted positively with both the monsoon trough and an AEW north of the AEJ but failed to develop into a tropical cyclone. The wave north of the AEJ brought Saharan air layer air masses inside the pouch that led to a drying of the circulation that may explain the decrease in convective activity.

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The characteristics of African easterly waves coupled to Saharan mineral dust aerosols

Cited by 24 publications

References 74 publications

Saharan Dust Transport during the Incipient Growth Phase of African Easterly Waves

Saharan Dust Transport during the Incipient Growth Phase of African Easterly Waves

Formation of a low‐level barrier jet and its modulation by dust radiative forcing over the Hexi Corridor in Central China on March 17, 2010

Dynamical study of three African Easterly Waves in September 2021

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