Effects of Meteorological Conditions on PM2.5 Concentrations in Nagasaki, Japan

Abstract

The fine particulate matter (PM2.5) problem has attracted much scientific and public attention, due to its effects on visibility, human health, and global climate. There are three factors that have important effect on PM2.5 mass concentration: domestic pollutant emission sources, external sources outside of the country, and the meteorological conditions. Nagasaki is a coastal prefecture located at the westernmost part of Japan, which is an ideal location to study pollutants from long range transport and correlation between PM2.5 and meteorological conditions. In this paper, PM2.5 concentration data and meteorological data were obtained during 1 January 2013~31 December 2013. The spatial distribution depicts that the western part of the study area has the most serious PM2.5 pollution. The correlation analysis results between PM2.5 concentration and meteorological data showed that temperature had a negative, and precipitation had a positive, correlation with PM2.5. There was a threshold in the correlations between humidity and wind speed and PM2.5. The correlation was positive or negative depending on the meteorological variable values, if these were lower or higher than the threshold. From the relationship with wind direction, it can be depicted that the west wind might bring the most pollutants to Nagasaki.

Modeling PM2.5 Urban Pollution Using Machine Learning and Selected Meteorological Parameters

“…This can result in increased levels of air pollution downwind from the original source, which directly depends on the wind direction [8]. Increased relative humidity has been shown to make even fine particles heavier, helping the dry deposition process of removal, while precipitation has a direct effect of scavenging by wet deposition [7,8]. In addition, some studies differentiate between the seasons, as different parameters have different effects during the year, due to the combination of conditions [8,9].…”

“…Therefore, temperature shows a reducing impact on fine particulate matter levels, through convection [7]. In addition, the formation and evolution of photochemical smog are dependent on solar radiation and temperature; meanwhile, wind speed tends to help ventilate air pollutants and/or transport them to other areas, even if the emission sources are not present in that region [8,9]. This can result in increased levels of air pollution downwind from the original source, which directly depends on the wind direction [8].…”

“…In addition, the formation and evolution of photochemical smog are dependent on solar radiation and temperature; meanwhile, wind speed tends to help ventilate air pollutants and/or transport them to other areas, even if the emission sources are not present in that region [8,9]. This can result in increased levels of air pollution downwind from the original source, which directly depends on the wind direction [8]. Increased relative humidity has been shown to make even fine particles heavier, helping the dry deposition process of removal, while precipitation has a direct effect of scavenging by wet deposition [7,8].…”

“…Increased relative humidity has been shown to make even fine particles heavier, helping the dry deposition process of removal, while precipitation has a direct effect of scavenging by wet deposition [7,8]. In addition, some studies differentiate between the seasons, as different parameters have different effects during the year, due to the combination of conditions [8,9]. Thus, it is clearly impossible to rely on a single parameter to fully understand the urban pollution, especially if the study area is in a nonhomogeneous and complex terrain.…”

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“…Fortunately, fractal theory is used to analyze the distribution of complex graphics. It has been widely used in art, astronomy, geography, biology, fluid dynamics, probability theory, chaos theory, and pure mathematics in the past few decades [14][15][16][17][18][19]. In recent years, the fractal theory was used to describe the propagation of cracks in rock or concrete specimens in laboratory [20][21][22][23][24][25].…”