The washout effect of summertime rain on surface air pollutants (O3, CO, NO2, SO2, and PM10) has been investigated over South Korea during 2002-2012 using routinely available air-monitored and meteorological data. Three new washout indices for PM10, SO2, NO2, and CO are developed to express the effect of precipitation scavenging on these pollutants. All of these pollutants show statistically significant negative correlations between their concentrations and rain intensity due to washout or convection. The washout effect is estimated for precipitation episodes classified by rain intensity (one set included all episodes and another included a subset of moderate intensity episodes that exclude Changma and typhoons), based on the log-transformed hourly data. The most sensitive air pollutant to the rain onset among these five air pollutants is PM10. The relative effect of the rainfall washout on the air pollutant concentrations is estimated to be: PM10SO2NO2>CO>O3, indicating that PM10 is most effectively scavenged by rainfall. The analysis suggests that the O3 concentrations may increase due to vertical mixing leading to its downward transport from the lower stratosphere/upper troposphere. The concentrations of CO are reduced, probably due to both the washout and convection. The concentrations of NO2 are affected by the opposing influences of lightning-generation and washout and this are discussed as well.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (NO. 2009-0083527 ) and the Korean Ministry of Environment as the Eco-technopia 21 project (NO. 201200016003). We would like to thank the Ministry of Environment of Korea (MEK), and the Korea Meteorological Administration (KMA) for providing air pollution and precipitation data, respectively. WRS thanks the National Oceanic and Atmospheric Administration for a grant to Howard University's NOAA Center for Atmospheric Sciences and the National Aeronautics and Space Administration for a grant to “Howard University Beltsville Center for Climate System Observation”.
All Science Journal Classification (ASJC) codes
- Environmental Science(all)
- Atmospheric Science