Transport Of Dust Aerosols Research Articles

An eddy-resolving simulation of the diurnal variation of fair-weather convection and tracer transport

Tracer transport in the atmosphere is controlled not only by synoptic-scale to mesoscale weather disturbances but also by microscale boundary-layer processes especially under fair-weather conditions. The present study investigates numerically the diurnal variation of boundary-layer convection and cumulus clouds and their role in transporting tracers by conducting high-resolution simulations that explicitly resolve turbulent eddies. The transport of dust aerosols in a desert area under two distinct stability conditions is specifically examined. Convection plays a significant role in transporting dust upward; in other words, the vertical depth of the dust transport is critically determined by the depth of convection. Deep convection is effective in transporting dust into the free atmosphere. The early morning stratification strongly regulates the temporal evolution and the vertical growth of convection and therefore the amount of tracer emission and transport. A sensitivity to model resolution of O (1 km) in a cloud-resolving simulation range is also examined. A proper parameterization for activating microscale convection is required for representing the diurnal variation of convection and tracer transport.

Variation of atmospheric turbidity coefficient and global solar radiation over Japan

Atmospheric aerosols affect on the global climate by changing the energy balance of earth-atmosphere system through scattering and absorption of solar radiation. Atmospheric turbiditycoefficients and global solar radiation were calculated in 14 cites in Japan from 1995 to 2005. Theatmospheric turbidity coefficient show increase in spring and decrease in autumn. The high values arederived from long range transport of dust aerosols originated in continent in China, or highconcentration of aerosols under by weak wind in calm day. The global solar radiation shows decreasefrom 1960 to 1980s, and shift to increase on reaching 1980s.

Desert dust aerosol columnar properties over ocean and continental Africa from Lidar in‐Space Technology Experiment (LITE) and Meteosat synergy

The new generation of spaceborne backscatter lidar systems, prefigured by the Lidar in‐Space Technology Experiment (LITE) mission in September 1994, will give new insight on the vertical distribution of both aerosols and clouds in the atmosphere. This is especially of importance for aerosols over land, where retrievals from passive sensors are known to be more difficult because of the surface contribution. Here we analyze mineral dust aerosol transport events through a new approach coupling the active LITE and passive Meteosat‐5 spaceborne observations. The Meteosat‐derived aerosol optical thickness at 550 nm is shown to be a good boundary condition for the lidar inversion in order to retrieve both the aerosol backscatter to extinction ratio (BER) and the aerosol extinction vertical profile above the Tropical Atlantic Ocean (TAO) and the Mediterranean Sea. Sensitivity tests indicate that the aerosol scattering coefficient is retrieved within a 20% relative uncertainty. Air mass trajectories allow us to further retrieve the vertical profile of aerosol optical properties over the continent in the Saharan Heat Low (SHL) region using the BER determined over the ocean. Results confirm a large dispersion of the BER which is not attributed to errors in the method. This shows the need to account for such dispersion in the retrieval of dust aerosol optical thickness and aerosol impact on the earth radiative budget. The coupling between LITE and Meteosat‐5 made here is shown to be interesting for an improvement of the direct dust aerosol forcing, and results should be improved by the CALIOP‐MODIS synergy.

Elemental characterization of airborne particles in Khartoum, Sudan

AbstractThe aim of this study was to investigate the elemental composition of airborne particles in the Khartoum area, particularly small inhalable particles of diameter ≤10 µm. Aerosol particles were collected during the period April–May 2001. The sampling was done using a dichotomous virtual impactor capable of separating airborne particles <2.5 µm in a fine mode and 2.5–10 µm particles in a coarse mode. Energy‐dispersive x‐ray fluorescence analysis was used to determine the elemental concentrations of 14 elements in the samples. Concentrations of black carbon were also measured on the two size fractions. The results obtained were compared with previous data from Khartoum and other African locations. Si, K, Ca, Ti, Mn, Fe, Zn and Sr were found to be dominant in the collected particulates. Day period collections were found to have higher elemental concentrations than those of night periods. This is attributed to higher traffic levels and wind speeds. The results show that dust aerosol transport and resuspension are the main sources that affect the quality of ambient air in the Khartoum area. The elemental concentrations from anthropogenic sources are generally low. Copyright © 2004 John Wiley & Sons, Ltd.

Dust records from three ice cores: relationships to spring atmospheric circulation over the Northern Hemisphere

Non-sea-salt Mg2+ (nssMg2+) records from three Northern Hemisphere ice cores (Mt. Everest, Himalayas; Mt. Logan, Yukon Territory; and 20D, southern Greenland) are presented as a proxy of atmospheric dust. NssMg2+ concentrations of both Mt. Everest and 20D ice core have increased since the 20th century. Relationships between the three ice core annual nssMg2+ series and instrumental sea-level pressure (SLP) series of spring (March–April–May) are investigated for the last century (AD 1899–1996), in order to develop an understanding of dust aerosol transport over the Northern Hemisphere during the spring season. On a hemispheric scale, an enhanced spring Arctic High weakens dust aerosol transport from central Asia to subarctic regions (e.g., southern Greenland and Yukon Territory), but strengthens transport of dust to the Himalaya (e.g., Mt. Everest). An intensification of the Siberian High may strengthen transport of dust aerosols to Greenland, and an enhancement of the Tibetan High strengthens transport to Himalaya and Yukon regions in spring. A stronger spring Azores High favors dust transport to both the Himalayas and south Greenland. On a regional scale, a deepened spring Icelandic Low and Aleutian Low increases transport of dust aerosols to Greenland and the Yukon Territory, respectively. Understanding these transport patterns is significant for the interpretation of ice core records and reconstruction of atmospheric circulation using longer records.

Glaciochemical records from a Mt. Everest ice core: relationship to atmospheric circulation over Asia

Glaciochemical records recovered from an 80.4 m ice core in the East Rongbuk (ER) Glacier (elevation: 6450 m) on the northern slope of Mt. Everest provide a reconstructing of past climate for the period AD 1846–1997. Empirical orthogonal function (EOF) analysis on the eight major ion (SO 4 2−, Mg 2+, Ca 2+, Na +, Cl −, NH 4 +, K +, and NO 3 −) time-series reveals inter-species relations and common structure within the ER glaciochemical data. The first two EOF series (EOF1-ions and EOF2-ions) are compared with instrumental data of sea level pressure (SLP) to demonstrate that the EOF-ions series display strong connections to winter (January) and summer (July) SLP over the Mongolian region. The positive relationship between EOF1-ions and the Mongolian High (MongHi) series suggests that enhanced winter MongHi strengthens the transport of dust aerosols southward from arid regions over central Asia to Mt. Everest. The close correspondence between EOF2-ions and the summer Mongolian Low (MongLow) indicates that the deeper MongLow, which is related to the stronger Indian Monsoon, contributes to a decrease in summer dust aerosols. Therefore, the ER ice core record comprises two assemblages of crustal species, each transported from different source regions during different seasons. EOF1-ions represents the majority of the crustal species and is related to winter atmospheric circulation patterns. These species are mainly transported from arid regions of central Asia during the winter dry season. EOF2-ions represents crustal species transported by summer atmospheric circulation from local/regional sources in the northern and southern Himalayas.

Study of emissions and transport of dust aerosol in Kalmykia black lands

Study of emissions and transport of dust aerosol in Kalmykia black lands