Skip to main content
SpringerLink
Log in

Mean kinematic characteristics of synoptic easterly disturbances over the Atlantic

  • Published:
Advances in Atmospheric Sciences Aims and scope Submit manuscript

Abstract

This study investigates the mean kinematic characteristics of the tropical Atlantic easterly disturbances in January–March (JFM), April–June (AMJ), July–September (JAS) and October–December (OND) from 1968–1998. For each season, the preferential tracks of these disturbances in the 3–10-day band periods were computed and spatialized, as well as their associated wavelength, velocity and main period, which lies between 3–5 days and between 6–9 days depending on the track and the season.

Two main tracks are highlighted over the Atlantic Ocean. During OND and JFM these two tracks are well separated and located in each hemisphere around 15°S and 12.5°N. From AMJ to JAS these tracks migrate northward; in JAS, they merge into one over the northern tropical Atlantic along 17.5°N. The associated wavelength fields exhibit a meridional gradient, with large wavelengths (greater than 4000 km) around the equator, between 5°N and 5°S, and smaller wavelengths outside of this latitude band (between 2500–3500 km). The phase speed is also found to exhibit poleward decreasing values from 12–6 m s−1.

Over the north Atlantic track, 6–9-day disturbances were found to occur from January to May and approximately from October to December. From June to September, the 3–5-day waves dominate the synoptic activity. Over the south Atlantic track, between May and August the synoptic variability is mainly explained by the 3–5-day disturbances but from January to April and from September to December both 3–5-day waves and 6–9-day waves can occur.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  • Burpee, R. W., 1972: The origin and structure of easterly waves in the lower troposphere in North Africa. J. Atmos. Sci., 29, 77–90.

    Article  Google Scholar 

  • Burpee, R. W., 1974: Characteristics of North African easterly waves during the summers of 1968 and 1969. J. Atmos. Sci., 31, 1556–1570.

    Article  Google Scholar 

  • Cadet, D. L., and S. H. Houston, 1984: Precipitable water over Africa and the Eastern/Central Atlantic ocean during summer 1979. J. Meteor. Soc. Japan, 62, 761–774.

    Google Scholar 

  • Cadet, D. L., and N.O. Nnoli, 1987: Water vapor transport over Africa and the Atlantic ocean during summer 1979. Quart. J. Roy. Meteor. Soc., 113, 581–602.

    Article  Google Scholar 

  • Carlson, T. N., 1969a: Some remarks on African disturbances and their progress over the tropical Atlantic. Mon. Wea. Rev., 97, 716–726.

    Article  Google Scholar 

  • Carlson, T. N., 1969b: Synoptic stories of three African disturbances that developed into Atlantic hurricanes. Mon. Wea. Rev., 97, 256–276.

    Article  Google Scholar 

  • Ceron, J. P., and J. F. Gueremy, 1999: Validation of the space-time variability of African easterly waves simulated by the CNRM GCM. J. Climate, 12(9), 2831–2855.

    Article  Google Scholar 

  • Ceron, J. P., J. F. Gueremy, and A. Sarr, 2001: African monsoon synoptic variability: Validation of the Meteo-France GCM. Physics and Chemistry of the Earth, (B): Hydrology, Oceans and Atmosphere, 26(2), 149–153.

    Article  Google Scholar 

  • Chang, C.-P., J. M. Chen, P. A. Harr, and L. E. Carr, 1996: North-westward-propagating wave patterns over the tropical western. North Pacific during summer. Mon. Wea. Rev., 124, 2245–2266.

    Article  Google Scholar 

  • Charney, J. G., and M. E. Stern, 1962: On the stability of internal baroclinic jets in a rotating atmosphere. J. Atmos. Sci., 19, 159–172.

    Article  Google Scholar 

  • Cohen, J. C. P., M. A. F. Silva Dias, and C. Nobre, 1995: Environmental conditions associated with amazonian squall lines: A case study. Mon. Wea. Rev., 123, 3163–3174.

    Article  Google Scholar 

  • de Félice, P., A. Viltard, D. Monkam, and C. Ouss, 1990: Characteristics of North African 6–9-day waves during summer 1981. Mon. Wea. Rev., 118, 2624–2633.

    Article  Google Scholar 

  • de Félice, P., A. Viltard, and J. Oubuih, 1993: A synoptic-scale wave of 6–9-day period in the Atlantic tropical troposphere during summer 1981. Mon. Wea. Rev., 121, 1291–1298.

    Article  Google Scholar 

  • Dickinson, M. J., and J. Molinari, 2000: Climatology of sign reversals of the meridional potential vorticity gradient over Africa and Australia. Mon Wea. Rev., 128, 3890–3900.

    Article  Google Scholar 

  • Dickinson, M. J., and J. Molinari, 2002: Mixed Rossby-Gravity waves and western Pacific tropical cyclogenesis Part I: Synoptic evolution. J. Atmos. Sci., 128, 3890–3900.

    Google Scholar 

  • Diedhiou, A., S. Janicot, A. Viltard, and P. de Félice, 1998a: Evidence of two regimes of easterly waves over West Africa and the tropical Atlantic. Geophys. Res. Lett., 25, 2805–2808.

    Article  Google Scholar 

  • Diedhiou, A., S. Janicot, A. Viltard, P. de Félice, and H. Laurent, 1998b: A fast eastern waves in West Africa troposphere. Meteor. Atmos. Phys., 69, 39–47.

    Article  Google Scholar 

  • Diedhiou, A., S. Janicot, A. Viltard, P. de Félice, and H. Laurent, 1999: Easterly waves regimes and associated convection over West Africa and the tropical Atlantic: Results from the NCEP/NCAR and ECMWF reanalyses. Climate Dyn., 15, 795–822.

    Article  Google Scholar 

  • Diedhiou, A., S. Janicot, A. Viltard, and P. de Félice 2001: Composite patterns of the easterly waves disturbances over West Africa and tropical Atlantic: A climatology from the 1979–1995 NCEP/NCAR reanalyses. Climate Dyn., 18, 241–253.

    Article  Google Scholar 

  • Diedhiou, A., S. Janicot, A. Viltard, and P. de Félice 2002: Energetics of the easterly waves disturbances over West Africa and tropical Atlantic: A climatology from the 1979–1995 NCEP/NCAR reanalyses. Climate Dyn., 18, 487–500.

    Article  Google Scholar 

  • Druyan, L. M., and T. M. Hall, 1994: Studies of African wave disturbances with the GISS GCM. J. Climate, 7, 261–276.

    Article  Google Scholar 

  • Duvel, J. P., 1990: Convection over tropical Africa and the Atlantic ocean during northern summer. Part II: Modulations by easterly waves. Mon. Wea. Rev., 118, 1855–1868.

    Article  Google Scholar 

  • Farge, M., 1992: Wavelets transform and their applications to turbulence. Annual Review of Fluid Mechanics, 24, 395–574.

    Article  Google Scholar 

  • Garreaud, R. D., 2000: Cold air incursions over subtropical South America: Mean structure and dynamics. Mon. Wea. Rev., 128(7), 2544–2559.

    Article  Google Scholar 

  • Garreaud, R. D., 2001: Subtropical cold surges: Regional aspects and global distribution. International Journal of Climatology, 21(10), 1181–1197.

    Article  Google Scholar 

  • Garreaud, R. D., and J. M. Wallace, 1998: Summertime incursions of midlatitude air into subtropical and tropical South America. Mon. Wea. Rev., 126(10), 2713–2733.

    Article  Google Scholar 

  • Grist, J. P., 2002: Easterly Waves over Africa. Part I: The Seasonal Cycle and Contrasts between Wet and Dry Years. Monthly Weather Review, 130, 197–211.

    Article  Google Scholar 

  • Kwon, H. J., 1989: A reexamination of the genesis of the African waves. J. Atmos. Sci., 46, 3621–3631.

    Article  Google Scholar 

  • Holton, J. R., 1979: An Introduction to Dynamic Meteorology. 2nd ed., Academic Press, New York, 416pp.

    Google Scholar 

  • Liebmann, B., and H. H. Hendon, 1990: Synoptic-scale waves near the equator. J. Atmos. Sci., 47, 1463–1479

    Article  Google Scholar 

  • Machado, L. A. T., R. L. Guedes, and M. A. S. Alves, 1997: Structural characteristics of convective systems and forcing of convection in South America observed by satellites (Características Estruturais de Sistemas Convectivos e Forçantes da conveção na América do Sul observados por satélites). Edição comemorativa dos dez anos do Climanálise, 110–122

  • Molinari, J., D. Knight, M. Dickinson, D. Vollaro, and S. Skubis, 1997: Potential vorticity, easterly waves, and tropical cyclogenesis. Mon. Wea. Rev., 125, 2699–2708.

    Article  Google Scholar 

  • Norquist, D. C., E. E. Recker, and R. J. Reed, 1977: The energetics of African wave disturbances as observed during Phase III of GATE. Mon. Wea. Rev., 105, 334–342.

    Article  Google Scholar 

  • Paradis, D., J. P. Lafore, and J. L. Redelsperger, 1995: African Easterly waves and convection. Part I: Linear simulations. J. Atmos. Sci., 52, 1657–1679.

    Article  Google Scholar 

  • Pytharoulis, I., and C. D. Thorncroft, 1999: The low-level structure of African easterly waves in 1995. Mon. Wea. Rev., 127, 2266–2280.

    Article  Google Scholar 

  • Reed, R. J., D. C. Norquist, and E. E. Recker, 1977: The structure and properties of African wave disturbances as observed during Phase III of GATE. Mon. Wea. Rev., 105, 317–333.

    Article  Google Scholar 

  • Reed, R. J., E. Klinder, and A. Hollingsworth, 1988: The structure and characteristics of African easterly wave disturbances determined from ECMWF operational analysis/forecast system. Meteor. Atmos. Phys., 38, 22–33.

    Article  Google Scholar 

  • Torrence, C., and G. P. Compo, 1998: A practical guide to wavelet analysis. Bull. Amer. Meteor. Soc., 79, 61–78.

    Article  Google Scholar 

  • Thompson, R. M., S. W. Payne, E. E. Recker, and R. J. Reed, 1979: Structure and properties of synopticscale wave disturbances in the intertropical convergence zone of the eastern Atlantic. J. Atmos. Sci., 36, 53–72.

    Article  Google Scholar 

  • Thorncroft, C. D., 1995: An idealized study of African easterly waves. Part I: More realistic basic states. Quart. J. Roy. Meteor. Soc., 121, 1589–1614.

    Article  Google Scholar 

  • Thorncroft, C. D., and B. J. Hoskins, 1994a: An idealized study of African easterly waves. Part I: A linear view. Quart. J. Roy. Meteor. Soc., 120, 953–982.

    Article  Google Scholar 

  • Thorncroft, C. D., and B. J. Hoskins, 1994b: An idealized study of African easterly waves. Part II: A nonlinear view. Quart. J. Roy. Meteor. Soc., 120, 983–1015.

    Article  Google Scholar 

  • Thorncroft, C. D., and M. Blackburn, 1997: On the maintenance of the African Easterly Jet. Quart. J. Roy. Meteor. Soc., 125, 763–786.

    Google Scholar 

  • Thorncroft, C. D., and K. Hodges, 2001: African easterly wave variability and its relationship to Atlantic tropical cyclone activity. J. Climate., 14(6), 1166–1179.

    Article  Google Scholar 

  • Viltard A., P. de Felice, and J. Oubuih, 1997: Comparison between the African and the 6–9-day disturbance patterns over West Africa during summer 1985. Meteor. Atmos. Phys., 62, 91–99.

    Article  Google Scholar 

  • Viltard, A., J. Oubuih, P. de Felice, and H. Laurent, 1998: Rainfall and 6–9-day wave-like disturbance in West Africa during summer 1989. Meteor. Atmos. Phys., 66, 229–234.

    Article  Google Scholar 

  • Wallace, J. M., G. H. Lim, and M. L. Blackmon, 1988: Relationship between cyclone tracks, anticyclone tracks, and baroclinic waveguides. J. Atmos. Sci., 45, 493–462.

    Article  Google Scholar 

  • Wheeler, M., and G. N. Kiladis, 1999: Convectively coupled equatorial waves: Analysis of clouds and temperature in the wavenumber-frequency domain. J. Atmos. Sci., 56, 374–399.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. IRD/LTHE, BP 53, 38041, Grenoble Cedex 9, France

    Arona Diedhiou & Henri Laurent

  2. CPTEC/INPE, Rod. Pdt. Dutra, Cachoeira Paulista, SP, Brasil

    Luiz A. T. Machado

Authors
  1. Arona Diedhiou
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Luiz A. T. Machado
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Henri Laurent
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Arona Diedhiou.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Diedhiou, A., Machado, L.A.T. & Laurent, H. Mean kinematic characteristics of synoptic easterly disturbances over the Atlantic. Adv. Atmos. Sci. 27, 483–499 (2010). https://doi.org/10.1007/s00376-009-9092-5

Download citation

  • Received:

  • Revised:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00376-009-9092-5

Key words

Search

Navigation