African Easterly Waves and Convection. Part I: Linear Simulations

Paradis, Denis; Lafore, Jean‐Philippe; Redelsperger, Jean‐Luc; Balaji, V.

doi:10.1175/1520-0469(1995)052<1657:aewacp>2.0.co;2

Cited by 33 publications

(30 citation statements)

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“…8a and 8b show that the KE has two midlevel maxima that flank either side of the AEJ axis, with the northern flank extending to the surface. In the NODUST experiment, the KE distribution is consistent with Thorncroft and Hoskins (1994) and Paradis et al (1995). Comparison of Figs.…”

Section: Global and Local Energeticsmentioning

confidence: 52%

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Effects of Saharan Dust on the Linear Dynamics of African Easterly Waves

Grogan

Nathan

Chen

2016

Journal of the Atmospheric Sciences

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The direct radiative effects of Saharan mineral dust aerosols on the linear dynamics of African easterly waves (AEWs) are examined analytically and numerically. The analytical analysis combines the thermodynamic equation with a dust continuity equation to form an expression for the dust-modified generation of eddy available potential energy GE. The dust-modified GE is a function of the transmissivity and spatial gradients of the dust, which are modulated by the Doppler-shifted frequency. The expression for GE predicts that for a fixed dust distribution, the wave response will be largest in regions where the dust gradients are maximized and the Doppler-shifted frequency vanishes. The numerical analysis uses the Weather Research and Forecasting (WRF) Model coupled to an online dust model to calculate the linear dynamics of AEWs. Zonally averaged basic states for wind, temperature, and dust are chosen consistent with summertime conditions over North Africa. For the fastest-growing AEW, the dust increases the growth rate from ;15% to 90% for aerosol optical depths ranging from t 5 1.0 to t 5 2.5. A local energetics analysis shows that for t 5 1.0, the dust increases the maximum barotropic and baroclinic energy conversions by ;50% and ;100%, respectively. The maxima in the generation and conversions of energy are collocated and occur where the meridional dust gradient is maximized near the critical surface-that is, where the Doppler-shifted frequency is small, in agreement with the prediction from the analytical analysis.

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Section: Global and Local Energeticsmentioning

confidence: 52%

“…These energy fields are commonly used to diagnose AEWs in the absence of dust (e.g., Thorncroft and Hoskins 1994;Paradis et al 1995).…”

Section: Global and Local Energeticsmentioning

confidence: 94%

Effects of Saharan Dust on the Linear Dynamics of African Easterly Waves

Grogan

Nathan

Chen

2016

Journal of the Atmospheric Sciences

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“…Therefore, more attention has been given to the regions of the western Pacific Ocean, the Caribbean Sea, West Africa, and the eastern Atlantic Ocean (Yanai et al 1968;Yanai and Nita 1967;Reed and Recker 1971;Albignat and Reed 1980;Thorncroft 1995;Paradis et al 1995;Hsieh and Cook 2005;Chen 2006;Berry et al 2007;among others). A few studies have focused on the South Atlantic tropical region, near the Brazilian coast (Yamazaki and Rao 1977;Kayano 2003;Hall 1989;Ferreira et al 1990;Coutinho and Fisch 2007).…”

Section: Introductionmentioning

confidence: 99%

Case Studies of Easterly Wave Disturbances over Northeast Brazil Using the Eta Model

Torres

Ferreira

2011

Weather and Forecasting

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This research aims to analyze two easterly wave disturbance events that reached the east coast of Northeast Brazil (NEB) on 15 May 2005 and 20 June 2006. The performance of the regional Eta Model was evaluated through four sets of experiments using different horizontal resolutions (10 and 40 km) and convective parameterization schemes [Betts-Miller-Janjić (BMJ) and Kain-Fritsch (KF)]. Through analysis of 700-hPa wind fields, all experiments, with 40-and 10-km horizontal resolutions and using the BMJ and KF schemes, were shown to well represent a trough propagating westward from about 208W to NEB, with a 5-day forecast range. When evaluating the model sensitivity to different convective parameterizations, all the experiments showed similar results and underestimated rainfall in most of the domain. The obtained results suggest the need to extend this analysis to a larger number of cases and to test other cumulus parameterizations in order to improve the rainfall forecast in eastern NEB.

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“…Operational forecasters are forced to combine the outputs from deficient NWP models with crude empirical rules. Our knowledge of the AEWs is dominated by three sources: the GATE data (e.g., Reed et al 1977), NWP analyses (e.g., Reed et al 1988;Diedhiou et al 1999), and theoretical models (e.g., Thorncroft and Hoskins 1994a,b;Paradis et al 1995). While Reed et al (1977) provided us with a valuable description of AEWs, our view is dominated by the composite analyses close to the West African coast.…”

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confidence: 99%