Airborne Measurements of High Pollutant Concentration Events in the Free Troposphere over the West Coast of South Korea between 1997 and 2011

Abstract

Aircrafts enable the direct measurement of chemical components in the free troposphere (FT). This study employed airborne measurements to examine the occurrences of high concentrations of SO 2 and NO x in the FT over the coastal region west of the Seoul metropolitan area, South Korea. The data from a long-term (1997-2011) airborne measurement campaign were used to determine the meteorological conditions favorable for carrying these pollutants into the Seoul area. The back trajectory analyses of 21 instances of high FT pollutant concentration events showed ascending patterns from the major pollutant sources, mainly the industrial complexes in eastern China, in 9 instances and passing patterns in 12 instances. In the ascending instances, developing low-pressure systems over the source regions provide favorable conditions to uplift air pollutants from the surface into the FT. In the passing instances, an anomalous low-pressure system near the surface prevented airflows from descending into the boundary layer and upper-level anticyclonic systems helped to keep the ascending airflows in the FT. This study proposes the basic mechanisms for predicting air quality in the Seoul area, considering that air pollutants in the FT often entrain into the boundary layer to increase local concentrations.

Atmospheric Boundary Layer—Free Troposphere Air Exchange in the North China Plain and its Impact on PM2.5 Pollution

“…The present result indicates that the complex terrain ventilation effect, as well as the cold front and low pressure synoptic conditions are most significant to the ABL‐FT exchange. These are consistent with the results of previous researches conducted in Europe, North America, and East Asia (Donnell et al., 2001; Lee et al., 2016; Lu & Turco, 1994; Oshima et al., 2013). Quantitatively, our correspondent exchange flux agrees to that calculated by Kiley and Fuelberg (2006) under the frontal system in the eastern United States (0.013 kg m −2 s −1 vs. 0.011 kg m −2 s −1 ).…”

PM2.5 Exchange Between Atmospheric Boundary Layer and Free Troposphere in North China Plain and Its Long‐Range Transport Effects

“…On large scale, the warm conveyor belt associated with frontal cyclones is the main mechanism of ABL vertical ventilation (Brown et al., 1984; Ding et al., 2009; Eckhardt et al., 2004). And the developing low‐pressure systems can also uplift air pollutants from the surface into the FT (Lee et al., 2016). Conversely, anticyclone circulation tends to cause downward transport (Sinclair et al., 2010).…”

“…Also, ABL-FT vertical exchange is active in this region due to the unique topography (with mountains to the west/northwest and coastline bordered to the east) and special geographical location (mid-latitude westerlies accompanied by diverse weather processes), as Jin et al (2021) indicated. Many observational and modeling studies have shown that the NCP could be an effective source area for long-range air pollutant transport above the ABL height, and discussed its impact on downstream regions such as the Yangtze River Delta (YRD) (Kang et al, 2019), Northeast China (NEC) (Ding et al, 2009;Sun et al, 2022), Japan (JAP) and South Korea (KOR) (Lee et al, 2016;Uno et al, 2017), and even the Trans-Pacific regions (Liu et al, 2003;Oshima et al, 2013). Most of these works are limited to the descriptions of short-term cases.…”

NO<sub>2</sub> and HCHO measurements in Korea from 2012 to 2016 from Pandora spectrometer instruments compared with OMI retrievals and with aircraft measurements during the KORUS-AQ campaign

“…The driving reason behind the interest is the effect of elevated levels of NO 2 in Korea on human health (Kim and Song, 2017 and references therein). Measurements of NO 2 from aircraft have been used to obtain altitude profiles to compare with data obtained from fixed site measurements and to obtain a national scale estimate of pollutant exposure (Lee et al, 2016;Kim and Song, 2017).…”