Yasunori Kurosaki

Effect of snow cover on threshold wind velocity of dust outbreak

[1] This study proposes parameters to measure the effect of snow cover on the threshold wind velocity of dust outbreak for dust models. We used statistics of snow cover, wind velocity and dust outbreaks in East Asia for the months of March and April for the years from 1988 to 2003. Dust events frequently occur in that region in those months, although snow and melting snow cover a broad area, making it difficult to know the distribution of dust from East Asia. Our equation, presented in this paper, shows the degree to which snow cover affects dust outbreaks. To validate this equation, we checked the correlation between frequency of strong winds and dust outbreaks. Our results showed that this correlation is improved when the effect of snow cover is considered. We discuss the effects of soil wetness, vegetation, and errors due to the subgrid heterogeneity of snow coverage as well. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3322 Meteorology and Atmospheric Dynamics: Land/ atmosphere interactions; 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; 9320 Information Related to Geographic Region: Asia. Citation: Kurosaki, Y., and M. Mikami (2004), Effect of snow cover on threshold wind velocity of dust outbreak, Geophys. Res. Lett., 31, L03106,

Variations in the structure of airborne bacterial communities in Tsogt-Ovoo of Gobi desert area during dust events

Asian dust events transport the airborne bacteria in Chinese desert regions as well as mineral particles and influence downwind area varying biological ecosystems and climate changes. However, the airborne bacterial dynamics were rarely investigated in the Gobi desert area, where dust events are highly frequent. In this study, air samplings were sequentially performed at a 2-m high above the ground at the sampling site located in desert area (Tsogt-Ovoo of Gobi desert; Mongolia 44.2304°N, 105.1700°E). During the dust event days, the bacterial cells and mineral particles increased to more than tenfold of concentrations. MiSeq sequencing targeting 16S ribosomal DNA revealed that the airborne bacteria in desert area mainly belonged to the classes Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Bacilli, Alpha-proteobacteria, Beta-proteobacteria, and Gamma-proteobacteria. The bacterial community structures were different between dust events and non-dust events. The air samples collected at the dust events indicated high abundance rates of Alpha-proteobacteria, which were reported to dominate on the leaf surfaces of plants or in the saline lake environments. After the dust events, the members of Firmicutes (Bacilli) and Bacteroidetes, which are known to form endospore and attach with coarse particles, respectively, increased their relative abundances in the air samples. Presumably, the bacterial compositions and diversities in atmosphere significantly vary during dust events, which carry some particles from grassland (phyllo-sphere), dry lake, and sand surfaces, as well as some bacterial populations such as Firmicutes and Bacteroidetes maintain in the atmosphere for longer time.

Association between Asian Dust-Borne Air Pollutants and Daily Symptoms on Healthy Subjects: A Web-Based Pilot Study in Yonago, Japan

During the spring, Asian dust (AD) repeatedly makes its way to Japan, originating from drylands. We evaluated the association between AD-borne air pollutants and daily reported subjective symptoms in healthy subjects. We constructed an Internet questionnaire on daily ocular, nasal, respiratory, and skin symptoms. Forty-two healthy volunteers residents of Yonago (mean age, 33.57) were selected from the self-reporting web-based survey and recorded their symptoms between 1 and 31 of March 2013. We also collected information on levels of suspended particulate matter (SPM), particulate matter < 2.5 µm (PM2.5), sulfur dioxide (SO2), and nitrogen oxide (NOx) per hour on each of those days. SPM and PM2.5 were the dominant pollutants recorded throughout the month. A positive correlation was observed between SPM and ocular (r = 0.475, p < 0.01), nasal (r = 0.614, p < 0.001), and skin (r = 0.445, p < 0.05) symptoms. PM2.5 correlations were significant for ocular (r = 0.428, p < 0.05), nasal (r = 0.560, p < 0.01), and skin (r = 0.437, p < 0.05) symptoms. Our findings provide introductory evidence of AD-borne air pollutants and their association with several bodily symptoms in healthy subjects with the implementation of a self-administrated web-based survey application.

Asian dust transport during the last century recorded in Lake Suigetsu sediments

Asian dust has a significant impact on the natural environment. Its variability on multiple timescales modulates the ocean biogeochemistry and climate. We demonstrate that temporal changes in the deposition flux of Aeolian dust recorded in sediments from Lake Suigetsu, central Japan, during the last century exhibit a continuous decreasing trend and a decadal-scale decrease in 1952–1974. The former decreasing trend can be explained by a decrease in the dust storm frequency at source regions due to the warming of Mongolia in the twentieth century, suggesting future decrease of Asian dust transport with further warming in Mongolia. Decadal-scale decrease of Aeolian dust is explained by weaker westerlies in lower latitudes in central Japan, reflecting a weaker Aleutian Low during the corresponding period. Decadal-scale westerly change probably causes north–south shifts of the dominant dust transport path, which affects subarctic northern Pacific Ocean biogeochemistry by changing the micronutrient iron supply.

Topographical and hydrological effects on meso-scale vegetation in desert steppe, Mongolia

This study investigated the seasonal variations of the normalized difference vegetation index (NDVI) and its relationships with climatic variables and topography in a small-scale (20 km×20 km) area (i.e., Tsogt-Ovoo village) within the desert steppe zone of Mongolia using in-situ observed climate data and satellite remote sensing data. We found that the topography is very important for vegetation growth in the desert steppe although the summer precipitation is the constraining factor. The unexpectedly high NDVI (up to 0.56), as well as the high aboveground biomass, in the valley bottom was primarily resulted from the topography-modulated redistribution of overland flow after relatively heavy precipitation events during the growing season. This makes the valley bottoms in desert steppes not only reliable feeding resources for livestock but also heavens for wild lives. But, the detected large standard deviation of annual maximum NDVI (NDVImax) from 2000 to 2013 in the valley bottom in response to rather variable precipitation implies that the valley bottoms under desert steppe climates are more vulnerable to climatic change.

Assessment of the Effects of Severe Winter Disasters (Dzud) on Public Health in Mongolia on the Basis of Loss of Livestock.

OBJECTIVE Mongolia experienced one of its most severe natural winter disasters (dzud) in 2009-2010. It is difficult to accurately assess the risk of the effects of dzud on human lives and public health. This study aimed to evaluate the Mongolian public health risks of dzud by assessing livestock loss. METHODS We analyzed data from all 21 provinces and Ulaanbaatar in Mongolia and compared the changes in infant mortality (2009-2010) and the decline in the numbers of livestock (percentage change from the previous year), which included horses, cattle, camels, sheep, and goats (2009-2010) and/or meteorological data. We also evaluated the association among the trends in the infant mortality rate, the number of livestock, and foodstuff consumption throughout Mongolia (2001-2012). RESULTS The change in the infant mortality rate was positively correlated with the rate of decreasing numbers of each type of livestock in 2010. Average temperature and total precipitation were not related to the change in the infant mortality rate. In the trend from 2001 to 2012, there was a significant positive correlation between the infant mortality rate and the number of livestock and the consumption of milk products. CONCLUSIONS Loss of livestock and shortage of milk products leading to malnutrition might have affected public health as typified by infant mortality in Mongolia. (Disaster Med Public Health Preparedness. 2016;10:549-552).

Prediction of health effects of cross-border atmospheric pollutants using an aerosol forecast model

Health effects of cross-border air pollutants and Asian dust are of significant concern in Japan. Currently, models predicting the arrival of aerosols have not investigated the association between arrival predictions and health effects. We investigated the association between subjective health symptoms and unreleased aerosol data from the Model of Aerosol Species in the Global Atmosphere (MASINGAR) acquired from the Japan Meteorological Agency, with the objective of ascertaining if these data could be applied to predicting health effects. Subjective symptom scores were collected via self-administered questionnaires and, along with modeled surface aerosol concentration data, were used to conduct a risk evaluation using generalized estimating equations between October and November 2011. Altogether, 29 individuals provided 1670 responses. Spearmans correlation coefficients were determined for the relationship between the proportion of the participants reporting the maximum score of two or more for each symptom and the surface concentrations for each considered aerosol species calculated using MASINGAR; the coefficients showed significant intermediate correlations between surface sulfate aerosol concentration and respiratory, throat, and fever symptoms (R = 0.557, 0.454, and 0.470, respectively; p < 0.01). In the general estimation equation (logit link) analyses, a significant linear association of surface sulfate aerosol concentration, with an endpoint determined by reported respiratory symptom scores of two or more, was observed (P trend = 0.001, odds ratio [OR] of the highest quartile [Q4] vs. the lowest [Q1] = 5.31, 95% CI = 2.18 to 12.96), with adjustment for potential confounding. The surface sulfate aerosol concentration was also associated with throat and fever symptoms. In conclusion, our findings suggest that modeled data are potentially useful for predicting health risks of cross-border aerosol arrivals.