Diurnal Variation of Vertical Ozone Distribution in the Southeastern Region of Korea: A Case Study of Ozonesonde Observations on January 29–30, 2024

Abstract

To analyze the altitude-dependent diurnal and nocturnal variations of ozone, four ozonesonde soundings were conducted in Ulsan on January 29-30, 2024. Ozonesonde measurements reveal a distinct diurnal variation in ozone within the planetary boundary layer (below 1 km) with daytime ozone concentrations around 0.06 ppm, dropping to around 0.03 ppm in early evening. In the free troposphere, ozone exhibited weak diurnal variations, except for a notable nighttime enhancement of 0.01 ppm or more above 1 km on January 30. Meterological factors were found to be less relevant in affecting the observed ozone enhancement. Meterological conditions, such as temperature, precipitation, and wind fields, were similar during the ozonesonde launches. Surface wind speeds were very low, suggesting minimal horizontal transport of ozone and its precursors from upwind regions. In this study, global (WACCM) and regional-scale (WRF-Chem) atmospheric chemical transport models were employed to link the observed ozone variations with the underlying dynamical and chemical factors as well as evaluate the consistency between simulation and observation. The global scale WACCM simulations indicate a higher contribution of stratospheric ozone intrusion to lower tropospheric ozone on January 30 than on January 29. The regional-scale WRF simulations well represent the vertical distribution of ozone on January 29, but exhibited a higher degree of uncertainty on January 30, highlighting the impact of stratospheric ozone on lower tropospheric air quality predictions. Continuous and more precise observations of the vertical distribution of ozone are expected to contribute significantly to air quality forecasting and studies utilizing ozone profile data.