Characterization of Some Elements of the Sahelian Climate and Their Interannual Variations for July 1983, 1984 and 1985 from the Analysis of METEOSAT ISCCP Data

Des̄bois, M.; Kayiranga, Théoneste; Gnamien, Brigitte; Guessous, Saad; Picon, Laurence

doi:10.1175/1520-0442(1988)001<0867:coseot>2.0.co;2

Cited by 79 publications

(53 citation statements)

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“…Rather than use sparse rain-gauge data, many researchers have based their studies of Sahelian precipitation systems on TIR satellite imagery (e.g. Desbois et al 1988;Duvel 1989Duvel ,1990Laing and Fritsch 1993;Rowell and Milford 1993). The geostationary Meteosat satellite, centred on the equator at the Greenwich Meridian, has proved particularly useful in this respect as it provides half-hourly TIR images (10.5-12.5 µm).…”

Section: Observing Land-atmosphere Coupling Using Satellite Data (A) mentioning

confidence: 99%

Observations of synoptic-scale land surface variability and its coupling with the atmosphere

Taylor

Parker

Lloyd

et al. 2005

Q. J. R. Meteorol. Soc.

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SUMMARYCloud-free brightness temperatures from satellite are used to interpret changes in the state of the land surface energy balance from day to day across the tropical semi-arid region of North Africa. The method provides an assessment of the spatial and temporal patterns in the surface characteristics. The variability in brightness temperature is closely linked to precipitation, as inferred from available rain-gauge data and satellite cold-cloud imagery. Temperatures drop sharply after rainfall, and increase gradually in subsequent days consistent with surface drying. The analysis shows that surface temperatures (and therefore fluxes) are well-organized at the synoptic scale, and can be linked to the westward propagation of mesoscale convective systems and African easterly waves (AEWs).The modulation of rainfall and cloud cover by weather systems is a key element in producing variability in surface fluxes of heat and moisture. To examine the relationships between surface variability and the atmosphere, a composite of anomalously warm (and dry) surface conditions with spatial coherence over a given longitude band is constructed from satellite data covering a single wet season. Operational analyses are used to examine atmospheric anomalies associated with these composited 'hotspots'. Surface moisture variations on the scale of several hundred km and larger can generate anomalous heat-lows during the day and, according to the operational analyses, generate cyclonic vorticity overnight. These vortices appear to be responsible for the observed modulation of cold cloud in the vicinity of the hotspot, and may influence the characteristics of AEWs in the Northern Sahel. Furthermore, theoretical ideas suggest that surface hotspots are likely to trigger a westward-propagating Rossbywave response; this process is demonstrated here in a simple numerical model.

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Section: Observing Land-atmosphere Coupling Using Satellite Data (A) mentioning

confidence: 99%

Observations of synoptic-scale land surface variability and its coupling with the atmosphere

Taylor

Parker

Lloyd

et al. 2005

Q. J. R. Meteorol. Soc.

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“…Le même problème existe d'ailleurs avec les mesures satellitaires. Mais il est ici en voie de résolution puisqu'un effort important d'homogénéisation a été entrepris ces dernières années (fichier ISCCP), ce qui a permis de développer les premières études touchant à la variabilité interannuelle des systèmes convectifs (Desbois et al 1988). De même, la disponibilité récente de mesures de flux par le programme multi-satellitairc ERBE peut offrir un premier aperçu de la variabilité interannuelle du bilan radiatif terrestre.…”

Section: Les Processus De Surface Continentauxunclassified

L'évolution des idées sur la variabilité interannuelle récente du cycle de l'eau atmosphérique en Afrique de l'ouest

Janicot¹,

Fontaine²

1993

Météorologie

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“…Climatologically, the AEJ is poleward (about 15 • N) of the summer rainfall maximum in West Africa, although many of the long-lived squall lines that traverse the region are observed to occur in the vicinity of the jet (e.g. Aspliden et al 1976;Bolton 1984;Desbois et al 1988;Rowell and Milford 1993;Hodges and Thorncroft 1997;Mathon and Laurent 2001).…”

Section: Introductionmentioning

confidence: 96%

Intense convective systems in West Africa and their relationship to the African easterly jet

Mohr

Thorncroft

2006

Quart J Royal Meteoro Soc

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SUMMARYFor May-September 1998, convective systems in West Africa were identified from observations by the Tropical Rainfall Measuring Mission satellite Microwave Imager at 85 GHz. Using re-analysis data, the 10-day average position of the African easterly jet (AEJ) was diagnosed from the 700 hPa zonal winds. The distance from each convective system's centroid to the axis of the AEJ was calculated. Each convective system's minimum brightness temperatures were ranked so that intense convective systems were defined as those in the 10th percentile or lower. The weak (>10th percentile) and intense convective systems were represented statistically as two separate populations, the weak by the skewed Gumbel distribution and the intense by the normal distribution. From May to August, the peak in activity of weak convective systems remained south of 10 • N but shifted east of 10 • E. The peak in activity of the intense convective systems followed the seasonal migration of the AEJ northwards and became increasingly separate from the peak in activity of weak convective systems. The majority of both weak and intense convective systems occurred within 0.50 • of high terrain. The high convective available potential energy, high-shear AEJ environment in the vicinity of high terrain appeared to have the greatest probability of generating intense convective systems in the study area.

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Characterization of Some Elements of the Sahelian Climate and Their Interannual Variations for July 1983, 1984 and 1985 from the Analysis of METEOSAT ISCCP Data

Cited by 79 publications

References 0 publications

Observations of synoptic-scale land surface variability and its coupling with the atmosphere

Observations of synoptic-scale land surface variability and its coupling with the atmosphere

L'évolution des idées sur la variabilité interannuelle récente du cycle de l'eau atmosphérique en Afrique de l'ouest

Intense convective systems in West Africa and their relationship to the African easterly jet

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