Etude de la dynamique de quelques lithométéores sahariens par télédétection spatiale

Oliva, P.; Coude, G.; Delannoy, Henry; Dorize, Lucien; Rognon, Pierre; Tabeaud, Martine

doi:10.3406/medit.1985.2300

Cited by 4 publications

(5 citation statements)

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“…For clear conditions during daytime the presence of atmospheric mineral dust over the arid areas of North Africa results in a global decrease of the longwave radiance outgoing to space. This effect, described in early studies [ Shenk and Curran , 1974; Legrand et al , 1983, 1985; Oliva et al , 1983], is the basis of an algorithm designed for the remote sensing of desert dust, using the thermal infrared channel (10.5–12.5 μm) of Meteosat satellites (pixel resolution varies between 160 km by 160 km and 225 km by 225 km from Sahelian to Moroccan regions). The method is described by King et al [1999] as the infrared contrast method.…”

Section: Methodsmentioning

confidence: 99%

Mineralogy of Saharan dust transported over northwestern tropical Atlantic Ocean in relation to source regions

2002

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[1] On the basis of daily Saharan dust samples collected at Sal Island (Cape Verde Archipelagos) and Barbados (Caribbean Sea) over 3 years, this study focuses on the mineralogical signature of the African sources providing dust over the tropical North Atlantic Ocean. First, the sources of the collected dust were localized by using relative clays abundance (illite-to-kaolinite ratio) combined with Meteosat infrared imagery, horizontal visibility, and backward trajectories of dusty air masses. Then, each identified source was linked to a single value of the illite-to-kaolinite ratio. Those results highlight that the clay content of the emitted dust depends directly on both the latitude and the longitude of the source. Dust originating from northwestern sources exhibits illite-tokaolinite ratios higher than those from Sahelian regions. Likewise, illite-to-kolinite ratio decreases from west to east.

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Section: Methodsmentioning

confidence: 99%

Mineralogy of Saharan dust transported over northwestern tropical Atlantic Ocean in relation to source regions

2002

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“…This was observed over the vast arid expanses of North Africa and Arabia, by Shenk and Curran [1974] using Nimbus THIR (temperature humidity infrared radiometer) data (10.5-12.5 gm), by Legrand et al [1983Legrand et al [ , 1985 and Oliva et al [1983] using Meteosat-IR channel(10.5-12.5 gm), and by Ackerman [1989] using 3.7 and 11 gm NOAA AVHRR (advanced very high resolution radiometer) data. This was observed over the vast arid expanses of North Africa and Arabia, by Shenk and Curran [1974] using Nimbus THIR (temperature humidity infrared radiometer) data (10.5-12.5 gm), by Legrand et al [1983Legrand et al [ , 1985 and Oliva et al [1983] using Meteosat-IR channel(10.5-12.5 gm), and by Ackerman [1989] using 3.7 and 11 gm NOAA AVHRR (advanced very high resolution radiometer) data.…”

Section: Introductionmentioning

confidence: 93%

“…In the first part of the desert dust cycle, during emission and the following atmospheric transport over the adjacent land, desert dust can be detected from space in the thermal infrared part of the spectrum. This was observed over the vast arid expanses of North Africa and Arabia, by Shenk and Curran [1974] using Nimbus THIR (temperature humidity infrared radiometer) data (10.5-12.5 gm), by Legrand et al [1983Legrand et al [ , 1985 and Oliva et al [1983] using Meteosat-IR channel(10.5-12.5 gm), and by Ackerman [1989] using 3.7 and 11 gm NOAA AVHRR (advanced very high resolution radiometer) data. The best sensitivity of the method was observed during the middle of the day with a decrease of the radiance outgoing to space, and also during the latter half of the night with an increase of this radiance [Legrand et at, 1988 Legrand, 1991] showing the potential of an infrared dust index for quantitative estimates of dust amount.…”

Section: Introductionmentioning

confidence: 93%

Satellite detection of dust using the IR imagery of Meteosat: 1. Infrared difference dust index

Legrand¹,

Plana-Fattori²,

N'Doumé³

2001

J. Geophys. Res.

222

228

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The Infrared Difference Dust Index (IDDI) is a satellite dust product designed for climatological applications, designed specifically for dust remote sensing in arid regions such as the Sahel and Sahara. It is based on the atmospheric response to dust, extracted from midday Meteosat‐IR imagery, and takes advantage of the impact of dust aerosols on the thermal infra‐red radiance outgoing to space. Simulations show a quasi‐linear relationship between satellite response to dust and shortwave optical depth, with a sensitivity depending on particle size distribution and radiative surface properties. Comparison of measured satellite response with photometric optical depth agrees with the simulations. Water vapor significantly affects the satellite signal for cases of large columnar amounts and oceanic air masses advected inland. Hence apart from possible coastal effects, the water vapor effect can be neglected in the Sahelian‐Saharan zone north of the Intertropical Convergence Zone, coinciding with the major regions of African dust emission and transport. The construction of the IDDI involves the processing of reference images, theoretically representing the outgoing radiance obtaining under clear‐sky conditions. Errors may arise from (1) dust remaining in the reference images and (2) seasonal shifts of the reference level; however, the latter error will be offset by averaging used in climatological processing. An error budget is presented for the station of Gao. A statistical comparison of IDDI data with visibility measured at synoptic stations results in (1) a validation of the product, and (2) a climatologically relevant visibility‐IDDI relation, valid for the arid regions of northern Africa. The latter relation is consistent with both simulations and photometric measurements. IDDI maps over Africa compare successfully with optical depth over adjacent ocean regions derived from Meteosat‐VIS imagery. The observed continuity of dust plumes across the African coast demonstrates the consistency between both products.

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“…Satellite observations offer an opportunity to make spatial extrapolations of local ground measurements, meteorological satellites being of particular interest for long term and large scale studies. It was recognized early on that remote sensing techniques could be used to detect desert dust clouds [Fujita, 1970;Prospero et al, 1970;Shenk and Curran, 1974], and satellite data have often been used for qualitative investigations of movements and source areas of individual dust plumes [e.g., Oliva et al, 1983;lwasaka et al, 1983;Legrand et al, 1985; Coudd-Gaussen et al, 1897; Bergametti et al, 1989b], or for long-term assessment of frequencies and source regions of dust conditions have already been published elsewhere Bergarnetti et al, 1989a;Dulac et al, 1989]. We shall focus here on the late June-early July 1985 period, during which a transport of dust particles from Africa was recorded [Bergametti et al, 1989b].…”

Section: Introductionmentioning

confidence: 99%

Assessment of the African airborne dust mass over the western Mediterranean Sea using Meteosat data

Dulac¹,

Tanré²,

Bergametti³

et al. 1992

J. Geophys. Res.

146

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The mass of African dust present over the western Mediterranean during a transport episode from northwestern Africa, which occurred in early July 1985, is estimated using a desert aerosol model, an Earth‐atmosphere radiative transfer model and Meteosat visible channel data from 4 days running. Dust pixels are selected from Meteosat images, and their aerosol optical thickness is retrieved. A proportionality factor between aerosol optical thickness and atmospheric columnar aerosol loading is computed and applied to the dust pixels. The total mass of atmospheric particles over the basin is obtained by interpolation and spatial integration. The maximum aerosol optical thickness is 1.8. The maximum aerosol columnar loading is evaluated to be 2.3 g m−2. The integrated mass of particles present at a given time is estimated to raise up to about 0.6 × 1012 g at the maximum and the total mass of dust exported from Africa to be of the order of 1012 g. The method is carefully evaluated and uncertainties are discussed, with particular emphasis on the relationship between atmospheric dust mass and aerosol optical depth. The overall uncertainty on the total mass is roughly a factor ±3. In the absence of clouds it appears that the major uncertainty results from the lack of knowledge of the actual mass‐size distribution of suspended dust particles, pointing out the lack of relevant data on particles larger than 10 μm in diameter. A simple calculation based on results from both computations and simultaneous field measurements yields a net transfer velocity of particles from the dust layer of approximately 1 cm s−1.

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Etude de la dynamique de quelques lithométéores sahariens par télédétection spatiale

Cited by 4 publications

References 0 publications

Mineralogy of Saharan dust transported over northwestern tropical Atlantic Ocean in relation to source regions

Mineralogy of Saharan dust transported over northwestern tropical Atlantic Ocean in relation to source regions

Satellite detection of dust using the IR imagery of Meteosat: 1. Infrared difference dust index

Assessment of the African airborne dust mass over the western Mediterranean Sea using Meteosat data

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