The Energetics and Propagation Dynamics of Tropical Summertime Synoptic-Scale Disturbances

Lau, K. M.; Lau, Ngar‐Cheung

doi:10.1175/1520-0493(1992)120<2523:teapdo>2.0.co;2

Cited by 145 publications

(125 citation statements)

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“…S8). Large-scale vertical ascent along the Intertropical Front contributes to the projected increases in AEW strength through vortex stretching (6,30). Additionally, the projected robust increase in deep vertical ascent along the Intertropical Front suggests the presence of increased latent heating (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Because AEWs north of the AEJ derive the majority of their energy from baroclinic processes associated with the interaction of the low-level meridional temperature gradients in the Sahel−Sahara region and the potential vorticity gradients in the AEJ core, the energetics of AEWs should in part reflect the local changes to surface air temperature that occur in response to enhanced radiative forcing. Stronger gradients in potential temperature result in greater zonal available potential energy for AEW growth (17,24,30). AEWs access this source of zonal available potential energy by fluxing temperature down the meridional temperature gradient, creating eddy available potential energy.…”

Section: Resultsmentioning

confidence: 99%

“…AEWs then grow by converting the eddy available potential energy to eddy kinetic energy through baroclinic overturning. To enable sustained AEW growth, the eddy available potential energy must be replenished by the zonal available potential energy (17,30).…”

Section: Resultsmentioning

confidence: 99%

“…They therefore exert a greater influence on precipitation variability in West Africa, and are more efficient at undergoing tropical cyclogenesis in the Main Development Region (MDR) (26) of the Atlantic (27)(28)(29). Although the northern vortices are primarily characterized by dry convective processes (30), they too are capable of influencing precipitation variability in the Sahel through the advection of moisture within the southerly flow of the vortex (31). In addition, because the northern vortices track near the southern border of the Sahara, they are an important source of Significance African easterly waves (AEWs) are ubiquitous weather disturbances over the tropical Atlantic basin during the summer season.…”

Section: Greenhouse Gas Forcing | Cmip5mentioning

confidence: 99%

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Projected changes in African easterly wave intensity and track in response to greenhouse forcing

Skinner¹,

Diffenbaugh

2014

Proc. Natl. Acad. Sci. U.S.A.

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Significance African easterly waves (AEWs) are ubiquitous weather disturbances over the tropical Atlantic basin during the summer season. However, despite the critical influence of AEWs on Sahel rainfall, transport of Saharan dust, and initiation of Atlantic hurricanes, little is known about how global warming influences AEW activity. We use an ensemble of general circulation models to investigate the response of AEWs to elevated greenhouse gas concentrations. We find that increases in regional temperature gradients and the strength of convergence and uplift along the Intertropical Front of Africa lead to increases in the strength of AEWs. Given the relationships that are observed in the current climate, changes in AEW strength could influence climate over both West Africa and the larger Atlantic basin.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Greenhouse Gas Forcing | Cmip5mentioning

confidence: 99%

See 2 more Smart Citations

Projected changes in African easterly wave intensity and track in response to greenhouse forcing

Skinner¹,

Diffenbaugh

2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Additionally the southwesterlies around the largescale trough over the Bay of Bengal bring the warm moist air to South Asia from the equatorial Indian Ocean ( Figure 5). Since the condensation heating associated with cumulus convection is the most significant energy source for the tropical disturbances [Lau and Lau, 1992], the largescale environment over the Bay of Bengal in P2 causes the slowdown of the decay of WDs in this region, resulting in that WDs tend to have a longer lifetime and be able to reach South Asia. Some WDs during the passage over South Asia …”

Section: Resultsmentioning

confidence: 99%

Seasonality of westward‐propagating disturbances over Southeast and south Asia originated from typhoons

Fudeyasu

Iizuka

Matsuura

2006

Geophysical Research Letters

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[1] We investigate the seasonal changes in the westwardpropagating disturbances (WDs) in Southeast and South Asia originated from typhoons over the western North Pacific. WDs tend to move over the northern part of the Indochina Peninsula and South Asia in summer, while over the southern part of the Indochina Peninsula and the Bay of Bengal in fall. Although the number of landfall on the Indochina Peninsula is the largest in fall, the active season for WD with a more west-oriented track is identified in late summer. The seasonality is related to large-scale atmospheric conditions. The easterly region throughout the latitude band 15°-25°N at 700 hPa during the active phases of intraseasonal variation in monsoon trough and the large-scale trough in lower troposphere over the Bay of Bengal are favorable conditions for taking the more west-oriented track of WD in late summer. Such conditions are found neither earlier summer nor fall.

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Consequences of systematic model drift in DYNAMO MJO hindcasts with SP‐CAM and CAM5

Hannah

Maloney

Pritchard

2015

J Adv Model Earth Syst

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Hindcast simulations of MJO events during the dynamics of the MJO (DYNAMO) field campaign are conducted with two models, one with conventional parameterization (CAM5) and a comparable model that utilizes superparameterization (SP-CAM). SP-CAM is shown to produce a qualitatively better reproduction of the fluctuations of precipitation and low-level zonal wind associated with the first two DYNAMO MJO events compared to CAM5. Interestingly, skill metrics using the real-time multivariate MJO index (RMM) suggest the opposite conclusion that CAM5 has more skill than SP-CAM. This inconsistency can be explained by a systematic increase of RMM amplitude with lead time, which results from a drift of the largescale wind field in SP-CAM that projects strongly onto the RMM index. CAM5 hindcasts exhibit a contraction of the moisture distribution, in which extreme wet and dry conditions become less frequent with lead time. SP-CAM hindcasts better reproduce the observed moisture distribution, but also have stronger drift patterns of moisture budget terms, such as an increase in drying by meridional advection in SP-CAM. This advection tendency in SP-CAM appears to be associated with enhanced off-equatorial synoptic eddy activity with lead time. Systematic drift moisture tendencies in SP-CAM are of similar magnitude to intraseasonal moisture tendencies, and therefore are important for understanding MJO prediction skill.

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The Energetics and Propagation Dynamics of Tropical Summertime Synoptic-Scale Disturbances

Cited by 145 publications

References 0 publications

Projected changes in African easterly wave intensity and track in response to greenhouse forcing

Projected changes in African easterly wave intensity and track in response to greenhouse forcing

Seasonality of westward‐propagating disturbances over Southeast and south Asia originated from typhoons

Consequences of systematic model drift in DYNAMO MJO hindcasts with SP‐CAM and CAM5

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