The Potential of Infrared Satellite Data for the Retrieval of Saharan-Dust Optical Depth over Africa

Legrand, Michel; Bertrand, Jean‐Louis; Des̄bois, M.; Menenger, L.; Fouquart, Y.

doi:10.1175/1520-0450(1989)028<0309:tpoisd>2.0.co;2

Cited by 65 publications

(53 citation statements)

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“…If dust is in the boundary layer, this surface effect is the main one and dust is viewed from space as a hot patch: in such a case the so-called IDDI would be negative. This nocturnal behavior of dust has been confirmed with observations (Legrand et al, 1989) and analysed with simulations (Legrand et al 1992). When dust layers are low, the above situation generally holds true.…”

Section: Nighttime Retrieval Of Dust Aerosols: Implications On Lw Radsupporting

confidence: 75%

Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part II: quantification of wind dependence and estimation of radiative forcing

2006

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Abstract. Long-range transport of continental dust makes these particles a significant constituent even at locations far from their sources. It is important to study the temporal variations in dust loading over desert regions and the role of meteorology, in order to assess its radiative impact. In this paper, infrared radiance (10.5-12.5 µm), acquired by the METEOSAT-5 satellite (∼5-km resolution) during 1999 and 2003 was used to quantify wind dependence of dust aerosols and to estimate the radiative forcing. Our analysis shows that the frequency of occurrence of dust events was higher during 2003 compared to 1999. Since the dust production function depends mainly on the surface wind speed over regions which are dry and without vegetation, the role of surface wind on IDDI was examined in detail. It was found that an increase of IDDI with wind speed was nearly linear and the rate of increase in IDDI with surface wind was higher during 2003 compared to 1999. It was also observed that over the Indian desert, when wind speed was the highest during monsoon months (June to August), the dust production rate was lower because of higher soil moisture (due to monsoon rainfall). Over the Arabian deserts, when the wind speed is the highest during June to August, the dust production rate is also highest, as soil moisture is lowest during this season. Even though nothing can be said precisely on the reason why 2003 had a greater number of dust events, examination of monthly mean soil moisture at source regions indicates that the occurrence of high winds simultaneous with high soil moisture could be the reason for the decreased dust production efficiency in 1999. It appears that the deserts of Northwest India are more efficient dust sources compared to the deserts of Saudi Arabia and Northeast Africa (excluding Sahara). The radiative impact of dust over various source regions is estimated, and the regionally and annually averaged top of the atmosphere dust radiative forcing (short wave, clear-sky and over land) over the entire study region (0-35 • N; 30 • -100 • E) was in the range of -0.9 to +4.5 W m −2 . The correspondingCorrespondence to: S. K. Satheesh (satheesh@caos.iisc.ernet.in) values at the surface were in the range of -10 to -25 W m −2 . Our studies demonstrate that neglecting the diurnal variation of dust can cause errors in the estimation of long wave dust forcing by as much as 50 to 100%, and nighttime retrieval of dust can significantly reduce the uncertainties. A method to retrieve dust aerosols during nighttime is proposed. The regionally and annually averaged long wave dust radiative forcing was +3.4±1.6 W m −2 .

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Section: Nighttime Retrieval Of Dust Aerosols: Implications On Lw Radsupporting

confidence: 75%

Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part II: quantification of wind dependence and estimation of radiative forcing

2006

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“…They also say that highly local effects, such as a busy road nearby, can influence aerosol quantity close to a station. With the relatively recent developments in remote sensing, and above all the emergence and use of several tools such as the Total Ozone Mapping Spectrometer absorbing Aerosol Index (TOMS AI) (Herman et al, 1997) and the Infrared Difference Dust Index (IDDI) (Legrand et al, 1989), research on dust emissions and its spatial distribution in the atmosphere has improved enormously in recent years (Engelstaedter et al, 2006).…”

Section: Origin and Movement Of Desert Dustmentioning

confidence: 99%

What do we know about effects of desert dust on air quality and human health in West Africa compared to other regions?

Longueville¹,

Hountondji²,

Henry³

et al. 2010

Science of The Total Environment

168

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This study aims to compare, on the one hand, the geographical distribution of the desert dust source areas, their contribution to quantities emitted into the atmosphere, the trajectories and the quantities deposited, with on the other hand the areas of research interest focused on the desert dust impacts on air quality and/or human health. Based on a systematic review of the literature using the ISI Web of Knowledge database, we found 231 articles published over the last decade on the desert dust impacts on air quality. Of these, 48% concerned Asian dust and 39% Saharan dust, with the remaining 13% divided between the other dust source areas. However, only one of these studies addressed the worsening air pollution in West Africa, even though it is very close to the Sahara, the greatest contributor to the global dust budget. Moreover, there have been very few studies (41) looking at the direct links between desert dust and human health; in this context too, no interest has been shown in West Africa. Yet this region is also among the areas in which morbidity rates have been noted to be far higher than those found in other regions of the world, and where respiratory infections alone account for more than 20% of the causes of infant mortality. This survey highlights a clear imbalance between those areas most exposed to dust and the most studied areas in terms of dust impacts. Given these findings and the often alarming results published about other regions of the world, we advocate a revival of interest in research on West Africa in order to achieve a better understanding of the desert dust impacts on air quality and health among the populations of this region.

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“…Subsequently, Legrand et al (1983Legrand et al ( , 1985, using METEOSAT infrared radiance data, studied dust aerosols over North Africa and Arabia. The studies carried out thereafter have demonstrated the potential of infrared radiance for quantitative estimates of dust aerosols (Ackerman, 1989;Legrand et al, 1989Legrand et al, , 1992Legrand et al, , 1994Legrand et al, , 2001Tanré and Legrand, 1991;Leon and Legrand, 2003).…”

Section: Problems In Quantification Of Dustmentioning

confidence: 99%

Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part I: sources and regional distribution

2006

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Abstract. Mineral dust constitutes the single largest contributor to continental aerosols. To accurately assess the impact of dust aerosols on climate, the spatial and temporal distribution of dust radiative properties is essential. Regional characteristics of dust radiative properties, however, are poorly understood. The magnitude and even sign of dust radiative forcing is uncertain, as it depends on a number of parameters, such as vertical distribution of dust, cloud cover and albedo of the underlying surface. In this paper, infrared radiance (10.5-12.5 µm), acquired from the METEOSAT-5 satellite (∼5-km resolution), was used to retrieve regional characteristics of dust aerosols for all of 1999. The infrared radiance depression, due to the presence of dust in the atmosphere, has been used as an index of dust load, known as the Infrared Difference Dust Index (IDDI). There have been several studies in the past carried out over the Sahara using IDDI as a measure of dust load. Over the Indian region, however, studies on dust aerosols are sparse. Spatial and temporal variability in dust loading and its regional distribution over various arid and semiarid regions of India and adjacent continents (0-35 • N; 30 • E-100 • E) (excluding Sahara) have been studied and the results are examined along with surface soil conditions (such as vegetation cover and soil moisture). The advantage of the IDDI method is that information on aerosol properties, such as chemical composition or microphysical properties, is not needed. A large day-to-day variation in IDDI was observed over the entire study region, with values ranging from 4 to 22 K. It was observed that dust activity starts by March over the Indian deserts, as well as over deserts of the Africa and Arabian regions. The IDDI reaches maximum during the period of May to August. Regional maps of IDDI, in conjunction with biomass burning episodes (using TERRA satellite fire pixel counts), suggest that large IDDI values observed during the winter months over Northern India could be due to a possible deposition of black carbon on larger dust aerosols. The IDDI values have beenCorrespondence to: S. K. Satheesh (satheesh@caos.iisc.ernet.in) compared with another year (i.e. 2003), with a large number of dust storms reported by meteorological departments based on visibility data. During the dry season, the magnitude of the monthly average IDDI during 2003 was slightly higher than that of 1999. The monthly mean IDDI was in the range from 4 to 9 K over the Indian deserts, as well as over the deserts of Africa and Arabia. The maximum IDDI during a month was in the range from 6 to 18 K. Large IDDI values were observed even over vegetated regions (such as the vegetated part of Africa and central India), attributed to the presence of transported dust from nearby deserts.

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The Potential of Infrared Satellite Data for the Retrieval of Saharan-Dust Optical Depth over Africa

Cited by 65 publications

References 0 publications

Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part II: quantification of wind dependence and estimation of radiative forcing

Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part II: quantification of wind dependence and estimation of radiative forcing

What do we know about effects of desert dust on air quality and human health in West Africa compared to other regions?

Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part I: sources and regional distribution

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