A three dimensional hydrostatic model named OASIS (Osaka University Atmospheric Simulation System) had been developed during 10 years from 1990. OASIS included the urban canopy model to calculate the longwave radiation and shortwave radiation into urban configurations. OASIS reasonably represented the sea and land breezes and the urban heat island in the Osaka Bay areas. The emission inventories of isoprene and monoterpene emitted from broad leaf trees and coniferous trees in the Kinki District were evaluated based on growth chamber experiments. The increase of ozone concentration, which was caused by the increase of biogenic volatile organic compounds due to global warming, was simulated by using these inventories. The calculations due to the reduction of nitrogen oxides from vessels showed that the ozone concentration in NO_X rich areas and the ozone concentration in hydrocarbon rich areas increased. From 2000, the community models have been generally used by many researchers accompanying the spread of internet and the progress of computer. Therefore WRF/CMAQ model was introduced in my laboratory in 2005. The calculations from this model showed that sulfate concentration in Japan was highly provided from transboundary pollution, that the generation of ozone was affected from biogenic and anthropogenic volatile organic compounds, and that the calculated organic aerosol concentration in PM_2.5 was underestimated.

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Since 1982, I have been investigating the effects of atmospheric environmental stresses on plants with my supervisors, colleagues and students of Izuta Laboratory at Faculty of Agriculture, Tokyo University of Agriculture and Technology. In this memorial review of the academic award in 2015 from the Japan Society for Atmospheric Environment, I reviewed the results of our experimental studies on the effects of ozone, soil acidification and excessive soil nitrogen due to acid deposition and aerosol (black carbon and ammonium sulfate particles) on growth, physiological functions such as photosynthesis and nutrient and water status of Japanese crops and forest tree species.

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Data assimilation was initially developed for numerical weather prediction (NWP) to obtain the appropriate initial and lateral conditions for the model simulations (forecasts) through a statistical combination of observation and short-range forecasts (Kalnay, 1999). Recently, progress in the observation and sophistication of the numerical model encourage data assimilation techniques to combine the Chemical Transport Model (CTM) and observations. The aim of this fusion is to be able to label events into the following four major objectives: (1) to obtain a more accurate state for forecasts (initial value problem), (2) to optimize parameters and forcing (emission) in the model (inverse modeling), (3) to generate a uniform, continuous and best-estimated data set (reanalysis), and (4) to investigate the potential impact of the observing system (Observation System Simulation Experiment; OSSE). This paper provides examples of the fusion along with the objectives.

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This paper assesses the use of water retentive pavement (WRP) made from fly ash as a mitigation strategy to urban heat island phenomenon. Our main objective is to develop a model using one-dimensional conservation equations to simulate the transport of heat and moisture in WRP. The evaporation efficiency, volumetric water content and matric potential were used as parameters. Under outdoor conditions, the thermal performance of WRP was compared with asphalt. Maximum surface temperature difference was from 10:00 JST to 15:00 JST, with asphalt being 9.1℃ warmer than WRP. Minimum surface temperature difference was from 22:00 to 06:00 JST, with asphalt 0.3℃ warmer than WRP. Calculation results show that the model can numerically evaluate the diurnal variation in surface temperature with 10.6% estimated error. Results of the temperature and water content profile imply that evaporation occurs first on the surface. The Average latent heat flux of WRP was 113.1 W/m² and 41.6 W/m² during the first and second day respectively. The reduction in daytime sensible heat flux by WRP compared with asphalt was 142.3 W/m². Reduction in nighttime conductive heat flux by WRP compared with asphalt was 30.9 W/m².

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A trend analysis of the benzo[a]pyrene (BaP) concentrations in Japan during the period from 2002 to 2012 was conducted using the monitoring data from the Ministry of the Environment of Japan. The sites are classified into three categories, i.e., general environment (I), stationary industrial region (H), and road site (E). It was found that the BaP trend values, [BaP], decrease in time with the associated seasonal variation, i.e., high in the autumn-winter and low in the summer. The contribution of emissions from the stationary industrial sources to [BaP] was found to be higher than that from mobile sources. The decreasing rate of [BaP] was 6.0%/yr for I, 4.6%/yr for H, 6.6%/yr for E for all of Japan. The higher [BaP] was found in H in Kyusyu and Setouchi, whereas [BaP] in the coastal area of the Sea of Japan was the lowest. It was found that the annual decreasing rate in I in all of Japan (6.8%/yr) during the period from 2005 to 2012 was 2.3 times higher than that (2.9%/yr) at the Noto monitoring site, facing the Sea of Japan. The contribution of the transboundary transport was estimated to be 11–34% in the coastal site of the Sea of Japan and 4–44% in the northern coastal sites of Kyusyu.

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A method to distribute the temporal emission in a thermal power plant, which is expected to improve the accuracy of the air pollution forecasting system, has been developed. A linear multiple regression formula, which estimates the hourly electric supply and demand energy in the future and which is based on the month, day of the week, clock time and discomfort index as explanation variables, was modeled. The result of the cross-validation during the testing period, not the same as the learning period to build it, indicated that the model is sufficiently reproducible. The hourly electric supply and demand energy in a gas-fired power plant and oil thermal power plant were estimated according to the energy ratio of the generation method, and its temporal distribution coefficient was calculated. Comparing the regression coefficients, the outstanding differences are estimated each clock time in the weekday and holidays, month, day of the week and discomfort index. Comparing the regression coefficients for 9 major electric power companies, the coefficients indicated that each area of the electric power company has its regional characteristic corresponding to its operating district area. Comparing the regression coefficients of the years 2008, 2010, 2012 and 2014 of TEPCO, the coefficients indicated that each year has its annual characteristic and the influence of power savings after the Great East Japan Earthquake in 2011. The results indicated the necessity to consider regional and annual characteristics while distributing the temporal emissions.

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O₃ is created by the reaction of OH and trace species in the atmosphere. The reactions are related to the anthropogenic and biogenic VOCs. Biogenic VOCs (BVOC) are measured as well as anthropogenic VOCs, and many kinds of BVOC measurements have been reported. The number of reports of BVOCs emitted from Sugi (Cryptomeria japonica) is limited, because Sugi is an endemic species in Japan. Though Sugi is the major species in Japan, only a few studies have reported BVOC emissions from Sugi. This is first study of Sugi to measure the total OH reactivity based on wild VOC measurements by PTR-MS and GC-FID. In this paper, the enclosure technique was used, and trace species emitted from Sugi was concurrently measured using the total OH reactivity measurement system and chemical analysis. β-farnesene contributed to 15.1% of the total OH reactivity. However 61.2% of the missing OH reactivity was found in this measurement. Even 23 major BVOCs were measured. The OH reaction rate coefficient of the unidentified species in the GC-FID chromatogram was determined. The reaction rate coefficient and OH reactivity of the biggest unidentified peak was determined to be 1.1×10^-10 cm³/molecule s, that was 18.1% of the total OH reactivity. Therefore, 56.9% of the total OH reactivity was identified.

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On 19 June 2013, the surface photochemical oxidant (Ox) concentration increased more than 100 ppbv over the Hokuriku region, while a depression with a baiu-front caused heavy rain. We investigated the mechanism of the increased Ox under the less photochemically active condition using meteorology observations and the chemical components, meteorological analysis data, and a numerical simulation conducted using the regional chemical transport model, NHM-Chem. We found that this event was characterized by multi-scale phenomena that consisted of the meso-α (200–2000 km) phenomenon over the coast of the Sea of Japan and the meso-β (20–200 km) phenomenon observed near the Noto Peninsula 1–2 h prior to the meso-α phenomenon. We estimated that the eastward high Ox flow at the post-front area caused the meso-α phenomenon. The analysis of the relative humidity and potential vorticity and NHM-Chem simulation revealed that the dry intrusion of stratospheric ozone occurred in the post-front area, which is caused by a folding of the dynamic tropopause on the northern side of the baiu-front. On the other hand, the increase in Ox with the meso-β scale occurred with a southward movement of shear caused by the cold air mass and southwesterly wind around the Noto Peninsula.

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