Hikari Shimadera

Numerical Evaluation of the Impact of Urbanization on Summertime Precipitation in Osaka, Japan

This study utilized the Weather Research and Forecasting (WRF) model version 3.5.1 to evaluate the impact of urbanization on summertime precipitation in Osaka, Japan. The evaluation was conducted by comparing the WRF simulations with the present land use and no-urban land use (replacing “Urban” with “Paddy”) for August from 2006 to 2010. The urbanization increased mean air temperature by 2.1°C in urban areas because of increased sensible heat flux and decreased mean humidity by 0.8 g kg−1 because of decreased latent heat flux. In addition, the urbanization increased duration of the southwesterly sea breeze. The urbanization increased precipitation in urban areas and decreased in the surrounding areas. The mean precipitation in urban areas was increased by 20 mm month−1 (27% of the total amount without the synoptic-scale precipitation). The precipitation increase was generally due to the enhancement of the formation and development of convective clouds by the increase in sensible heat flux during afternoon and evening time periods. The urbanization in Osaka changes spatial and temporal distribution patterns of precipitation and evaporation, and consequently it substantially affects the water cycle in and around the urban areas of Osaka.

Evaluation of Air Quality Model Performance for Simulating Long-Range Transport and Local Pollution of PM2.5 in Japan

The Community Multiscale Air Quality Model (CMAQ) v5.0.2 was applied to PM2.5 simulation in Japan, which is strongly affected by long-range transport (LRT) from anthropogenic sources in the Asian Continent, for one year from April 2010 to March 2011. The model performance for LRT and local pollution (LP) of PM2.5 was evaluated to identify the model processes that need to be improved. CMAQ well simulated temporal and spatial variation patterns of PM2.5 but underestimated the concentration level by 15% on average. The contribution of LRT was estimated from the difference between the baseline simulation case and a zero-emission case for anthropogenic emissions in the continent. The estimated LRT contribution to PM2.5 was 50% on average and generally higher in the western areas of Japan (closer to the continent). Days that were dominantly affected by LRT or LP were determined based on the contribution of LRT to sulfate, which was fairly well simulated and strongly affected by LRT among major PM2.5 components. The underestimation of PM2.5 was larger in LP days (by 26% on average) than LRT days (by 10% on average). Therefore, it is essential to improve local emissions, formation, and loss processes of precursors and PM2.5 in Japan.

Evaluation of mercury concentration in the lake biwa-yodo river basin by a one-box multimedia model and model sensitivity on the experimentally determined water-sediment partition coefficient

Abstract Considering the environmental damage caused by mercury, evaluating mercury concentrations in four environmental media, namely the atmosphere, water, soil, and sediment, is necessary. Available data on mercury emissions and

Impact of field biomass burning on local pollution and long-range transport of PM2.5 in Northeast Asia

Biomass burning (BB), such as, crop field burning during the post-harvest season, emits large amounts of air pollutants (e.g., PM2.5) that severely impact human health. However, it is challenging to evaluate the impact of BB on PM2.5 due to uncertainties in the size and location of sources as well as their temporal and spatial variability. This study focused on the impacts of BB on local pollution as well as the long-range transport of PM2.5 in Northeast Asia resulting from a huge field BB event in Northeast China during the autumn of 2014. Air quality simulations using the Community Multiscale Air Quality (CMAQ) model were conducted in the year 2014 over the horizontal domains covering Northeast Asia, including the Japanese mainland. In the baseline simulation (Base), field BB emissions were derived from Fire INventory from NCAR (FINN) v1.5 for the year 2014. The model reasonably captured the daily mean PM2.5 mass concentrations, however, it underestimated concentrations in autumn around Northeast China where irregular field BB following the harvest occurred frequently. To address the underestimation of emissions from BB sources in China, another simulation with boosted BB sources from cropland area (FINN20_crop) was conducted in addition to the Base simulation. The model performance of FINN20_crop was significantly improved and showed smaller biases and higher indices of agreement between simulated and observed values in comparison to those of Base. To evaluate long-range transport of PM2.5 from BB sources in China towards Japan, CMAQ with brute-force method (CMAQ/BFM)-estimated BB contributions for Base and FINN20_crop cases were compared with Positive Matrix Factorization (PMF)-estimated BB contributions at Noto Peninsula in Japan. The CMAQ/BFM-estimated contributions from FINN20_crop were in greater agreement with the PMF-estimated contributions. The comparison of BB contributions estimated by the two contrasting models also indicated large underestimations in the current BB emission estimates.

Evaluation of the impact of aerosol direct effect on wintertime PM 2.5 simulation in East Asia

Numerical simulations were performed in order to evaluate the impact of the direct effect of aerosol particles on meteorology and air quality over East Asia. The online coupled Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) modeling system was applied from January to March 2014 for cases with/without feedback: two-way/one-way simulations. Ground-level shortwave radiation and PM2.5 concentration in the two-way simulation were respectively smaller and higher than those in the one-way simulation over the Asian Continent, particularly in China with remarkably high PM2.5 concentration. These differences indicate that the aerosol direct effect substantially influence the atmospheric stability, and therefore the dispersion efficiency of air pollutants.

Relation of particle matter on roadside tree leaves with traffic density and road dust

In Japan, air pollution due to atmospheric particulate matter has been a serious problem, especially at roadsides in megacity areas. However, it is difficult to widely cover roadside areas with a limited number of air pollution monitoring stations. Therefore we focused on a biomonitoring technique by using leaves of roadside trees. We sampled leaves of ginkgo (G. biloba) along major arteria roads in Osaka City, which is the third largest city in Japan. The particles retained on the surfaces of the sampled leaves were removed by ultrasonic cleaning in ethanol solution. The ethanol solution including particles was suctioned by an aspirator and particles were collected on a PTFE filter. Elements collected on the filter were quantified by particle induced X-ray emission (PIXE) analysis. It was found that the mass of traffic-related elements on the surfaces of sampled leaves correlated with the traffic density of large vehicles and the distance from the end of roadside to the sampling point. The ratios of mass of road dust-related elements on sampled leaves were almost similar to those of the road dust profile data. These results suggest the biomonitoring technique is an effective method to assess roadside air pollution.