Modification of mineral dust particles by cloud processing and subsequent effects on drop size distributions

Wurzler, S.; Reisin, Tamir; Levin, Zev

doi:10.1029/1999jd900980

Cited by 229 publications

(192 citation statements)

References 34 publications

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“…The dust-induced reduced r e and suppressed precipitation are further supported by the observation of comparable amounts of cloud water within these clouds, indicated by similar maximum values of the vertically polarized 85-GHz brightness temperatures by the TRMM passive microwave imager. The progressive enhancement of the coalescence farther away from the dust source can be attributed to the decreasing amounts of dust, probably aided by the wet coagulation and cleaning process described by Wurzler et al (9).…”

Section: Satellite Observations Of Cloud-dust Interactionsmentioning

confidence: 98%

Desert dust suppressing precipitation: A possible desertification feedback loop

Rosenfeld

Rudich

Lahav

2001

Proc. Natl. Acad. Sci. U.S.A.

706

512

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The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process. Satellite Observations of Cloud-Dust InteractionsT he three major sources of aerosols in the atmosphere are desert dust, smoke from biomass burning, and anthropogenic air pollution. The latter two are recognized as sources of large concentrations of small cloud condensation nuclei (CCN), which lead to the formation of a high concentration of small cloud droplets and therefore to an increased cloud albedo (1) and suppressed precipitation (2). Desert dust that passes over polluted areas often can be coated by sulfur due to chemical processes on their surface (3). These particles then can serve as giant CCN, which may enhance the collision and coalescence of droplets and therefore increase warm precipitation formation and decrease the clouds' albedo (4). However, our satellite, aircraft, and laboratory observations show that mineral dust suppresses precipitation. Possible causes for this apparent contradiction are discussed later.Data from the Advanced Very High-Resolution Radiometer (AVHRR) onboard the National Oceanographic and Atmospheric Administration satellite were used for retrieving properties of clouds that formed during a heavy dust storm in March 1998 over the Eastern Mediterranean. The satellite image is shown in Fig. 1, using the microphysical color scheme of Rosenfeld and Lensky (5). The dust rapidly advected from the Sahara through Southern Israel, Jordan, and Syria and curled back through Turkey into the center of a cyclonic depression over Cyprus. A ''tongue'' of dust-free air converged into the cyclone from the north and west. Shallow convective clouds of similar depth and shapes developed over the sea and the adjacent land in both dust laden and dust-free regions. Retrieval of cloud microstructure (see Fig. 2) reveals that the droplets in clouds that formed in the dust-free zone had large effective radii (r e ) that steeply increased with heigh...

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Section: Satellite Observations Of Cloud-dust Interactionsmentioning

confidence: 98%

Desert dust suppressing precipitation: A possible desertification feedback loop

Rosenfeld

Rudich

Lahav

2001

Proc. Natl. Acad. Sci. U.S.A.

706

512

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“…In addition to mineral dust particles serving as ice nuclei (IN) (e.g. DeMott et al, 2003;Ansmann et al 2008), the increase in hygroscopicity may also transform dust into effective cloud condensation nuclei (CCN) (Johnson, 1982;Wurzler et al, 2000;Sassen et al, 2003;Lohmann and Feichter, 2005;Twohy et al, 2009a) and thereby affect the formation and distribution of clouds and precipitation (e.g. Kelly et al, 2007), thus also altering the radiative impact of clouds.…”

Section: Introductionmentioning

confidence: 99%

CALIPSO observations of transatlantic dust: vertical stratification and effect of clouds

et al. 2012

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Abstract. We use CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios, as well as particulate retrievals during the summer of 2007 to study transatlantic dust properties downwind of Saharan sources, and to examine the influence of nearby clouds on dust. Our analysis suggests that (1) under clear skies, while lidar backscatter and color ratio do not change much with altitude and longitude in the Saharan Air Layer (SAL), depolarization ratio increases with altitude and decreases westward in the SAL; (2) the vertical lapse rate of dust depolarization ratio, introduced here, increases within SAL as plumes move westward; (3) nearby clouds barely affect the backscatter and color ratio of dust volumes within SAL but not so below SAL. Moreover, the presence of nearby clouds tends to decrease the depolarization of dust volumes within SAL. Finally, (4) the odds of CALIOP finding dust below SAL next to clouds are about 2/3 of those far away from clouds. This feature, together with an apparent increase in depolarization ratio near clouds, indicates that particles in some dust volumes loose asphericity in the humid air near clouds, and cannot be identified by CALIPSO as dust.

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“…When first emitted, dust particles are often composed of insoluble or low-solubility components. In modeling studies, the assumption is sometimes made that cloud droplets cannot nucleate on these particles (Wurzler et al, 2000;Yin et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Influence of dust composition on cloud droplet formation

Kelly

Chuang

Wexler

2007

Atmospheric Environment

128

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Previous studies suggest that interactions between dust particles and clouds are significant; yet the conditions where dust particles can serve as cloud condensation nuclei (CCN) are uncertain. Since major dust components are insoluble, the CCN activity of dust strongly depends on the presence of minor components. However, many minor components measured in dust particles are overlooked in cloud modeling studies. Some of these compounds are believed to be products of heterogeneous reactions involving carbonates. In this study, we calculate with diameters between about 0.6 and 2 µm under some conditions. Dust particles > 2 µm often activate regardless of their composition. Only under very specialized conditions does the addition of a dust distribution into a rising parcel containing fine (NH 4 ) 2 SO 4 particles significantly reduce the total number of activated particles via water competition. Effects of dust on cloud saturation and droplet number via water competition are generally smaller than those reported previously for sea salt. Large numbers of fine dust CCN can significantly enhance the number of activated particles under certain conditions. Improved representations of dust mineralogy and reactions in global aerosol models could improve predictions of the effects of aerosol on climate.

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Modification of mineral dust particles by cloud processing and subsequent effects on drop size distributions

Cited by 229 publications

References 34 publications

Desert dust suppressing precipitation: A possible desertification feedback loop

Desert dust suppressing precipitation: A possible desertification feedback loop

CALIPSO observations of transatlantic dust: vertical stratification and effect of clouds

Influence of dust composition on cloud droplet formation

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