Abstract
To investigate the characteristics of air pollutants transported from the Asian continental regions to the marine boundary layer of the northern South China Sea (SCS), we recorded the continuous measurements of meteorology, sea surface radiative budget, and ozone (O3) and related compounds in the marine boundary layer near Taiwan during 2010 cruises. For the marine field campaign investigation, the contaminated O3 and related compounds (e.g., NO2, NO, CO, CH4, and NMHC) have been eliminated from research vessel's exhaust by using various meteorological factors. The mean values of O3 and its major precursors (NO2, NO, and CO) were 25 ± 9.9, 3.2 ± 1.8, 2.9 ± 1.7, and 204 ± 54 ppb, respectively. A high O3 mixing ratio is related to extreme shortwave radiation, high air temperature, less precipitation, and low wind speed and specific humidity. The results indicated a higher ∆O3/∆CO ratio of 0.2 at sunset during the March 2010 cruise mainly due to a long-range transport of aged plumes (> 3 days) originating from the super-region of Asian continent and a lower ∆O3/∆CO ratio of 0.12 at midday, mostly associated with the proximity to local sources of fresh plumes (< 2 days) during April 2010 and July 2010 cruises. The O3 and related compounds mixing ratios over the ocean are affected by emission source, Asian monsoon, wind speed, gas deposition, gas solubility, the chemical enhancement factor, the frontal inversion and the boundary layer height. A clear bulge in the diurnal cycle was observed between early morning and late afternoon for NOx, CO, and O3. Moreover, 5-d backward trajectories and Southeast Asia surface wind fields suggested that the southward export of the air masses in spring originated from Mongolia and the East Asian continent.
Highlights
O3 plays a crucial role in transferring atmospheric radiation, atmospheric oxidation, maintaining air quality, and the enhancement of the greenhouse effect (Lelieveld et al, 2004)
To investigate the characteristics of air pollutants transported from the Asian continental regions to the marine boundary layer of the northern South China Sea (SCS), we recorded the continuous measurements of meteorology, sea surface radiative budget, and ozone (O3) and related compounds in the marine boundary layer near Taiwan during 2010 cruises
Valid Data Excluding Interference from the R/V Exhaust The contaminations produced by the vessel itself should be considered when equipment is used for continuous monitoring over the ocean
Summary
O3 plays a crucial role in transferring atmospheric radiation, atmospheric oxidation, maintaining air quality, and the enhancement of the greenhouse effect (Lelieveld et al, 2004). High ozone and CO concentrations plus positive correlation of O3–CO in springtime indicated that the enhancements of O3 probably resulted from photochemical O3 production (Lin et al, 2011). Because the atmospheric lifetime of O3 ranges from a few weeks to a few months, O3 serves as an effective indicator for distinguishing air-mass sources from the Asian continent or the marine boundary layers. Debaje and Kakade (2009) indicated that an abrupt supply of NOx and NMHCs and increased incoming shortwave radiation (SW) result in a high photochemical O3 mixing ratio. Meteorology plays a crucial role in the formation, dispersion and transport of O3 and related compounds. Debaje and Kakade (2009) indicated that an abrupt supply of NOx and NMHCs and increased incoming shortwave radiation (SW) result in a high photochemical O3 mixing ratio. Cheng et al (2013) observed a strong correlation between a high O3 concentration and the anticyclone weather type, which is typically associated with clear skies, strong solar insolation, high diurnal temperature ranges, and warm temperature, which are favorable for a high O3 mixing ratio
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