Asian Dust

Considerable deposition of (137)Cs was observed in the northwestern coastal area of Japan in March 2002. Since there were no nuclear explosions or serious nuclear accidents in the early 2000s, transport of previously contaminated dust appears to be the only plausible explanation for this event. In March 2002, there was a massive sandstorm on the East Asian continent, and the dust raised by the storm was transported across the sea to Japan. This dust originated in Mongolia and northeastern China, in an area distant from the Chinese nuclear test site at Lop Nor or any other known possible sources of (137)Cs. Our radioactivity measurements showed (137)Cs enrichment in the surface layer of grassland soils in the area of the sandstorm, which we attributed to accumulation as a result of past nuclear testing. We suggest that the grassland is a potential source of (137)Cs-bearing soil particles. Since the late 1990s, this area has experienced drought conditions, resulting in a considerable ...

h i g h l i g h t s < We calculated the respective radiative forcing of dust and non-dust part of the Asian dust plumes. < Vertically resolved optical properties of the aerosols derived by Lidar were used as inputs for RTM. < The non-dust particles contributed larger to the radiative forcing at the surface than the dusts. < Asian dust radiative forcing can be enhanced largely due to non-dust particles mixed into dust layer. < Pollution particles play a key role in stabilizing the dust layer by increasing the heating rates.

Low molecular weight (C 1 -C 10 ) monocarboxylic acids, dissolved organic carbon and major inorganic ions in alpine snow pit sequence from a high mountain site, central Japan Abstract Snowpack samples were collected from a snow pit sequence (6 m in depth) at the Murodo-Daira site near the summit of Mt. Tateyama, central Japan, an outflow region of Asian dusts. The snow samples were analyzed for a homologous series of low molecular weight normal (C 1 -C 10 ) and branched (iC 4 -iC 6 ) monocarboxylic acids as well as aromatic (benzoic) and hydroxy (glycolic and lactic) acids, together with major inorganic ions and dissolved organic carbon (DOC). The molecular distributions of organic acids were characterized by a predominance of acetic (range 7.8-76.4 ng/g-snow, av. 34.8 ng/g) or formic acid (2.6-48.1 ng/g, 27.7 ng/g), followed by propionic acid (0.6-5.2 ng/g, 2.8 ng/g).

Decades-long monitoring of anthropogenic radionuclides in the atmospheric deposition in Tsukuba, Japan suggests not only the substantial impacts of the Asian dust (Kosa) on the deposition but also the possible change of the Kosa source region, especially during springs of the 2000s. In order to know more about such change, 4 single wet deposition events occurred in the spring of 2007 were scrutinized. The largest anthropogenic radionuclides wet deposition was supplied by the April 2-4 event. It brought several tens % of the monthly depositions (April 2007) of the dust (residue) mass (4.5 g m À2 ) and anthropogenic radionulides ( 90 Sr: 16, 137 Cs: 97 and Pu: 3 mBq m À2 ). None of the events observed fulfilled both criteria of the specific activities and 90 Sr/ 137 Cs activity ratio to the Tsukuba soil; they did not exhibit local soil dust signature. The Kosa events in fact have extensive impacts on the atmospheric environment over Japan in spring season. Considering the elevated specific activities as well as greater 137 Cs/ 90 Sr activity ratio in the deposited dust, it is hypothesized that the dust source areas in Asian continent would be shifting from the arid zone to the desert-steppe zone suffering from desertification during the 2000s. This type of the Kosa may be called as the 'new-regime Kosa'. Chemical observation in the far downwind region of the Kosa dust could allow us to know possible shift in the source regions.

The effects of El Niño/Southern Oscillation (ENSO) under negative Arctic Oscillation (AO) phase on the Asian dust activity are investigated for springs of the period 1961-2002. The spring dust index (DI) describing the monthly frequencies of three types of dust events (e.g. dust storm, blowing dust, and floating dust) exhibits a significant increase in the years of negative AO phase (hereafter AO−) and El Niño, compared with that in the years of AO− and La Niña. Averaged over all observation stations, the spring DI (49.7) during the El Niño/AO− years is higher by 11.4% or 29.8% than that (38.3) during the La Niña/AO− years. We suggest possible physical mechanism that the anomalous large-scale environments associated with AO− and El Niño are more effective to provide favourable conditions to enhance Asian dust activity. During the El Niño/AO− years, meridional gradients of pressure and temperature over the dust source regions are significantly enhanced by decreasing the geopotential height and warming air temperature that originated from the north and south of source regions, respectively, under the influence of AO− and El Niño. These also intensify the zonal wind shear and atmospheric baroclinicity, thereby producing enhanced cyclogenesis and dust occurrences over the major source regions. At the same time, dust transport paths with the stronger westerly winds are developed by the combined constraints of anomalous cyclone over the Siberia and the Mongolia and anomalous anticyclone over the western North Pacific, and thus strengthen dust transport to the downwind regions.

This study analyzes the regional and temporal distributions of PM 10 concentrations observed in major metropolitan cities in Korea before, during and after a recent Asian dust episode in 2002. There were spatial and temporal variations in PM 10 concentrations among the mid-western, the southwestern, the southeastern, and the southern parts of Korea during this Asian dust period due to the different air mass movement time and the different wind directions and speeds of prevailing winds in each city or region. The origins of the three-day Asian dust episode were identified by an analysis of two-day backward isentropic air trajectories. The different origins for each day also significantly contributed to the spatial and temporal variations in PM 10 concentrations. A significant relationship was found between PM 10 concentrations on the day preceding the first peak day and the first peak day of the Asian dust period but only in the mid-western areas. The concentrations of PM 10 just after the Asian dust episode were much higher than those just before. There was a significant increase in a coarse fraction, having soil origins, of particles during the Asian dust episode. Concentrations of Mn, Fe, Ni and Cr extracted from the total suspended particulate (TSP) samples collected in 7 cities during the Asian dust episode were much higher when compared with other days in 2001. However, the Asian dust did not consistently increase the concentrations of lead, cadmium and copper as they are influenced by local sources such as local traffic or industrial emissions.

1] Aerosol data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, air mass backward trajectories, land use maps, soil characteristics maps, diagnostic ratios of elemental composition, and multivariate linear regression were utilized as part of a semi-quantitative analysis. The purpose of the analysis was to determine the types of dust-causing events that contribute to low visibility at a given site when the sum of extinction from coarse mass (CM) and fine soil (FS) was larger than any other aerosol component and the reconstructed aerosol extinction coefficient was among the 20% highest (calculated on a calendar

Asian Dust (AD) particles transported from source areas contribute to sharp increases in coarse particles in Japan. We examined the association of exposure to AD events with emergency ambulance dispatches in Nagasaki city. We also examined whether AD transported at different altitude routes from source areas influenced dispatch rates. Using lidar (light detection and ranging), we determined moderate AD days (0.066/km <dust extinction coefficient ≤0.105/ km) and heavy AD days (0.105/km <dust extinction coefficient). We applied a time-stratified case-crossover analysis to estimate the association between AD days and emergency ambulance dispatches. There were 9,070 dispatches from March to May during 2003-2007. The heavy AD events at cumulative lag0-3 were associated with an increase in emergency dispatches due to all causes by 12.1% (95% confidence interval (CI), 2.3, 22.9) and an increase for those due to cardiovascular diseases by 20.8% (95% CI: 3.5, 40.9). We categorized 31 AD days based on backward trajectory analyses into AD days with lower altitude routes and those with higher altitude routes. We observed a greater increase in emergency ambulance dispatches on AD days with lower altitude routes compared with those on AD days with higher altitude routes although the difference was not significant (p for interaction 0.49). These results have shown that exposure to high AD particle levels could increase emergency ambulance dispatches due to illnesses such as cardiovascular stress, and that AD traveling through different routes may have different health effects.

The effects of El Niño/Southern Oscillation (ENSO) under negative Arctic Oscillation (AO) phase on the Asian dust activity are investigated for springs of the period 1961-2002. The spring dust index (DI) describing the monthly frequencies of three types of dust events (e.g. dust storm, blowing dust, and floating dust) exhibits a significant increase in the years of negative AO phase (hereafter AO−) and El Niño, compared with that in the years of AO− and La Niña. Averaged over all observation stations, the spring DI (49.7) during the El Niño/AO− years is higher by 11.4% or 29.8% than that (38.3) during the La Niña/AO− years. We suggest possible physical mechanism that the anomalous large-scale environments associated with AO− and El Niño are more effective to provide favourable conditions to enhance Asian dust activity. During the El Niño/AO− years, meridional gradients of pressure and temperature over the dust source regions are significantly enhanced by decreasing the geopotential height and warming air temperature that originated from the north and south of source regions, respectively, under the influence of AO− and El Niño. These also intensify the zonal wind shear and atmospheric baroclinicity, thereby producing enhanced cyclogenesis and dust occurrences over the major source regions. At the same time, dust transport paths with the stronger westerly winds are developed by the combined constraints of anomalous cyclone over the Siberia and the Mongolia and anomalous anticyclone over the western North Pacific, and thus strengthen dust transport to the downwind regions.

Asian dust storms frequently occur in northeast Asia and the dust occasionally even spreads as far as North America during spring. Asian dust can be harmful to human health and the environment, and thus has become one of the most serious problems for Asian countries. In the present study, we evaluated sensitization to Asian dust in Japanese patients with rhinoconjunctivitis. In March 2011, a prospective, non-randomized, cross-sectional study was conducted in 10 patients with allergic rhinoconjunctivitis (allergic group), 3 patients with atopic keratoconjunctivitis (atopic group), and 10 age- and sex-matched healthy control subjects (control group). Skin prick tests (SPT) were performed with untreated Asian dust, Asian dust extract, heat-sterilized Asian dust, silicon dioxide (SiO2), and phosphate-buffered saline (PBS). A panel of 14 allergen extracts was also tested, comprising extracts of pollens (cedar, orchard grass, ragweed, and mugwort), house dust (house dust mixture and Derma...

1] Aerosol optical properties (aerosol optical thickness, Å ngström exponent, size distribution, and single scattering albedo) over east Asia were examined using long-term measurements of sky radiation at Mandalgovi, Dunhuang, Yinchuan, and Sri-Samrong sites of the Skyradiometer Network (SKYNET). Also included were sky radiation measurements at Anmyon, Gosan in Korea, and Amami-Oshima in Japan during April for examining optical properties of Asian dust. Results show that the seasonal average of aerosol optical thickness (AOT) generally exhibits a maximum in spring and a minimum in autumn over east Asia. At Sri-Samrong and Yinchuan, relatively distinct seasonal cycles are noted, in comparison to the arid desert regions of Dunhuang and Mandalgovi. In general, aerosol size distributions are characterized by a bimodal pattern, with a fine mode around 0.2 mm and a coarse mode around 2À5 mm. Similar to AOT and a, volume spectra are also much dependent on geographical location and season. Dunhuang mostly shows coarse mode particles in all seasons, while Mandalgovi and Sri-Samrong show large seasonal variations in the total volume of fine mode particles. The single scattering albedos of dust particles over east Asia are around 0.9 at 0.5 mm, which are larger than the previously known values of 0.63-0.89 but similar to those found in the Aerosol Robotic Network (AERONET) analysis. It is noted that the optical properties of Asian dust around Korea and Japan are quite similar to those found in dust source regions such as Dunhuang and Mandalgovi. However, the single scattering albedo appears to be smaller than those observed in Dunhuang and Mandalgovi. Furthermore, single scattering albedo tends to become smaller during the dust outbreak period. Considering that aerosols in Korean and Japanese areas are much influenced by anthropogenic aerosols emitted in China particularly under the westerly conditions, the mixing processes between different aerosol species may be the cause of the different optical properties of Asian dust.

This study compares characteristics of particulate matter measured in Ulsan and Incheon, Korea, before, during, and after March and April Asian dust (AD) events in the year 2002. The concentrations of PM 10 just after the AD periods in Ulsan were much higher than those just before the event, during normal spring days. In Incheon, the average PM 10 concentrations during the first peak period of the AD event showed a significant correlation for 24 h average concentrations just before the first peak period. However, a correlation between concentrations in Ulsan was much weaker than those found in Incheon. The ratio of PM 2.5 to PM 10 concentrations in Ulsan during the AD event was much higher than those after the AD event. Even though there was a large increase in PM 10 concentrations during the AD event compared to normal spring days, there were no large differences in concentrations of PM 2.5 between them. Concentrations of Mn, Fe, Ni, Cr, Al, Ca, and Mg extracted from the total suspended particulate (TSP) collected during the AD event were very high as compared to those after the event. However, the concentrations of Pb and Cu contained in the TSP decreased during the AD event. A comparison of ozone and PM 10 concentrations during the AD events shows that extremely high dust concentrations combined with lower sunshine duration time may significantly reduce the ambient ozone concentrations. r

We present detailed 3D structure of Asian dust outflow from a dust source region to the northwestern Pacific ocean retrieved by NASA/CALIOP onboard CALIPSO and results simulated by a four-dimensional variational (4DVAR) data assimilation version of a dust transport model (RC4) based on the NIES Lidar network. The modeled and CALIOP dust extinction showed good agreement, both for horizontal scale (600-1200 km) and vertical depth (1600-3600 m) near the dust source regions. Cross-section analyses of CALIOP and RC4 assisted by forward trajectory revealed that dust from the Gobi Desert on 5 May traveled approximately 1000-1500 km/day to the east and passed over Japan on 8 May. The elevated dust subsequently passed to the Pacific Ocean while maintaining the major dust layer height of 2500-4000 m MSL trapped within the potential temperature of 302-306 K. Results of our analyses demonstrate the importance of integration of CALIOP measurement and the dust model for clarifying the overall structure of an Asian dust event.

Decades-long monitoring of anthropogenic radionuclides in the atmospheric deposition in Tsukuba, Japan suggests not only the substantial impacts of the Asian dust (Kosa) on the deposition but also the possible change of the Kosa source region, especially during springs of the 2000s. In order to know more about such change, 4 single wet deposition events occurred in the spring of 2007 were scrutinized. The largest anthropogenic radionuclides wet deposition was supplied by the April 2-4 event. It brought several tens % of the monthly depositions (April 2007) of the dust (residue) mass (4.5 g m À2 ) and anthropogenic radionulides ( 90 Sr: 16, 137 Cs: 97 and Pu: 3 mBq m À2 ). None of the events observed fulfilled both criteria of the specific activities and 90 Sr/ 137 Cs activity ratio to the Tsukuba soil; they did not exhibit local soil dust signature. The Kosa events in fact have extensive impacts on the atmospheric environment over Japan in spring season. Considering the elevated specific activities as well as greater 137 Cs/ 90 Sr activity ratio in the deposited dust, it is hypothesized that the dust source areas in Asian continent would be shifting from the arid zone to the desert-steppe zone suffering from desertification during the 2000s. This type of the Kosa may be called as the 'new-regime Kosa'. Chemical observation in the far downwind region of the Kosa dust could allow us to know possible shift in the source regions.

Garrison is a coral reef ecologist; her research focuses on the effects of global-scale processes on coral reef ecosystems in the Caribbean and in the Pacific Ocean. Shinn has published more than 100 scientific articles concerning geology, limestone diagenesis, and the geologic history and growth of coral reefs in Florida, the Bahamas, the Persian Gulf, the Marshall Islands, and Puerto Rico. Griffin studies transoceanic transport of microorganisms in the atmosphere. Holmes specializes in the biogeochemical cycles of short-lived radionuclides and reconstruction of the paleoenvironment from coral skeletons. Kellogg works on characterizing the microbial communities in African dust and polluted sediments. William T. Foreman is a research chemist at USGS National Water Quality Laboratory, Box 25046, Denver, CO 80225; he develops and applies methods to characterize the transport and fate of organic chemical contaminants in air, water, sediment, and biota. Michael S. Majewski is a research chemist at USGS, 6000 J Street, Sacramento, CA 95819; his research interests include the environmental behavior and fate of organic contaminants, their long-range atmospheric transport and deposition, and the effects of air pollution on water quality. Laurie L. Richardson is an associate professor in the Department of Biology, Florida International University, Miami, FL 33199; her area of expertise is microbial physiological ecology, with a focus on the role of microorganisms in the etiology of coral diseases. Kim B. Ritchie is a scientist at MicroGenomics Inc., 5935 Darwin Court, Carlsbad, CA 92008; her research interests include molecular biology, marine microbial communities, and marine pathogens in the Atlantic and Pacific Oceans. Garriet W. Smith is an associate professor at the University of South Carolina-Aiken, 471 University Parkway, Aiken, SC 29801; he is a microbial ecologist interested in the ecology of marine microorganisms, particularly disease pathogens.

1] Aerosol optical properties (aerosol optical thickness, Å ngström exponent, size distribution, and single scattering albedo) over east Asia were examined using long-term measurements of sky radiation at Mandalgovi, Dunhuang, Yinchuan, and Sri-Samrong sites of the Skyradiometer Network (SKYNET). Also included were sky radiation measurements at Anmyon, Gosan in Korea, and Amami-Oshima in Japan during April for examining optical properties of Asian dust. Results show that the seasonal average of aerosol optical thickness (AOT) generally exhibits a maximum in spring and a minimum in autumn over east Asia. At Sri-Samrong and Yinchuan, relatively distinct seasonal cycles are noted, in comparison to the arid desert regions of Dunhuang and Mandalgovi. In general, aerosol size distributions are characterized by a bimodal pattern, with a fine mode around 0.2 mm and a coarse mode around 2À5 mm. Similar to AOT and a, volume spectra are also much dependent on geographical location and season. Dunhuang mostly shows coarse mode particles in all seasons, while Mandalgovi and Sri-Samrong show large seasonal variations in the total volume of fine mode particles. The single scattering albedos of dust particles over east Asia are around 0.9 at 0.5 mm, which are larger than the previously known values of 0.63-0.89 but similar to those found in the Aerosol Robotic Network (AERONET) analysis. It is noted that the optical properties of Asian dust around Korea and Japan are quite similar to those found in dust source regions such as Dunhuang and Mandalgovi. However, the single scattering albedo appears to be smaller than those observed in Dunhuang and Mandalgovi. Furthermore, single scattering albedo tends to become smaller during the dust outbreak period. Considering that aerosols in Korean and Japanese areas are much influenced by anthropogenic aerosols emitted in China particularly under the westerly conditions, the mixing processes between different aerosol species may be the cause of the different optical properties of Asian dust.

As a part of the effort to understand the structure of long-range transported aerosol plumes and local pollution, aerosol observations monitored the mass concentrations and number-size distributions during the period August 2006 to July 2009 near the top of Mt. Haruna (1365 m), an isolated mountain in the Kanto Plain in Japan. The mass concentrations observed at Mt. Haruna and plain sites showed a seasonal variation with a maximum in spring and summer, respectively. The spring peaks in aerosols at Mt. Haruna were probably caused by long-range transport of mineral dust and anthropogenic particles from the Asian continent. The summer peaks at the plain sites was attributed to local pollution from the Tokyo metropolitan area. Three examples of 2007 Asian dust events were investigated to show that aerosols may be dispersed in a complicated three-dimensional structure and that delayed arrivals of the dust plumes at plain sites compared to Mt. Haruna were not a rare case. Because of the boundary layer being stable at night, the dust layer was advected eastward without the vertical mixing before sunrise. This study suggests that after thermal convection activated by sunlight during daytime Asian dust transported in the free troposphere may be brought down into the atmospheric boundary layer, increasing the dust concentration there.

The entrainment process of water vapor into the dust layer during Asian dust events and the effect of water vapor associated with the Asian dust layer (ADL) on aerosol hygroscopic properties are investigated. The entrainment processes of water vapor into the ADL is examined by using a PSU/NCAR MM5 together with the backward trajectory model, radiosonde data, and remotely sensed aerosol vertical distribution data. Two dust events in the spring of 1998 and 2001 are examined in detail. The results reveal that the water vapor mixing ratio (WVMR) derived by the MM5 fits in well with the WVMR observed by radiosonde, and is well coincident with the aerosol extinction coefficient (s ep) measured by the micropulse lidar. The temporal evolution of the vertical distributions of WVMR and s ep exhibited similar features. On the basis of a well simulation of the enhanced water vapor within the dust layer by the MM5, we trace the dust storms to examine the entrainment mechanism. The enhancement of WVMR within the ADL was initiated over the mountainous areas. The relatively moist air mass in the well-developed mixing layer over the mountainous areas is advected upward from the boundary layer by an ascending motion. However, a large portion of the water vapor within the ADL is enhanced over the edge of a highland and the plains in China. This is well supported by the simulated WVMR and the wind vectors. Aircraftbased in situ measurements of the chemical and optical properties of aerosol enable a quantitative estimation of the effect of the enhanced WVMR on the aerosol hygroscopic properties. The submicron aerosol accompanied by the dust storm caused an increase of aerosol scattering through water uptakes during the transport. This increase could be explained by the chemical fact that water-soluble submicron pollution aerosols are enriched in the ADL.

Measurements of size-resolved particle number concentrations during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) field campaign were made at the Gosan super-site, South Korea. In East Asia, dust and precipitation phenomena play a crucial role in atmospheric environment and climate studies because they are major sources and sinks of atmospheric aerosols, especially in the springtime. Total Ozone Mapping Spectrometer (TOMS) Aerosol Index and backward trajectories are analyzed to investigate the spatial and temporal evolution of dust storms. The size distributions between dust and non-dust periods and times with and without precipitation are compared. In order to understand the temporal evolution of the aerosol size distribution during dust and precipitation events, a simple aerosol dynamics model is employed. The model predicted and observed size distributions are compared with the measured data. The results show that the coarse mode particle number concentrations increase by a factor of 10-16 during dust events. During precipitation, however, particles in the coarse mode are scavenged by impaction mechanism. It is found that the larger particles are more efficiently scavenged. The degree of scavenged particle varies depending on the rainfall rate, raindrop size distribution and aerosol size distribution.