[1] We report results of a cloud chemistry numerical modeling intercomparison, which shows good agreement among gas-aqueous photochemistry box models that are being used in the community. For the case studied, cloud chemistry depleted concentrations of CH 2 O, CH 3 OOH, HNO 3 , and O 3 , while H 2 O 2 (in the absence of sulfur chemistry), NO, and NO 2 increased. Because parcels of air usually flow in and out of cloud in a matter of minutes rather than remain in cloud for an hour, an optional simulation was performed in which frequent brief cloud encounters were represented. Representing a cloud intermittently rather than continuously does not alter the total concentration of many of the species. However CH 2 O and HCOOH concentrations are decreased and increased, respectively, because of the timing of the CH 2 O production during clear-sky intervals and its destruction during cloudy intervals. Further differences between a continuous cloud simulation and an intermittent cloud simulation are expected if pH is allowed to vary during the cloud periods. Simulating an intermittent cloud brought out the importance of using a chemistry time step that is a multiple of the cloud time step because deviations of results from a simulation in which the chemistry time step did not coincide with the appearance and disappearance of cloud were quite large. To better quantify the effect of cloud on HO x photochemistry, future investigations should include nonmethane hydrocarbon and sulfur chemistry. Future cloud chemistry modeling intercomparisons should bring in cloud physical and chemical measurements so that the models can be evaluated with observations.

Abstract. Topic 3 of the Model Inter-Comparison Study for Asia (MICS-Asia) Phase III examines how online coupled air quality models perform in simulating high aerosol pollution in the North China Plain region during wintertime haze events and evaluates the importance of aerosol radiative and microphysical feedbacks. A comprehensive overview of the MICS-Asia III Topic 3 study design, including descriptions of participating models and model inputs, the experimental designs, and results of model evaluation, are presented. Six modeling groups from China, Korea and the United States submitted results from seven applications of online coupled chemistry–meteorology models. Results are compared to meteorology and air quality measurements, including data from the Campaign on Atmospheric Aerosol Research Network of China (CARE-China) and the Acid Deposition Monitoring Network in East Asia (EANET). The correlation coefficients between the multi-model ensemble mean and the CARE-China observed near-surface air pollutants range from 0.51 to 0.94 (0.51 for ozone and 0.94 for PM2.5) for January 2010. However, large discrepancies exist between simulated aerosol chemical compositions from different models. The coefficient of variation (SD divided by the mean) can reach above 1.3 for sulfate in Beijing and above 1.6 for nitrate and organic aerosols in coastal regions, indicating that these compositions are less consistent from different models. During clean periods, simulated aerosol optical depths (AODs) from different models are similar, but peak values differ during severe haze events, which can be explained by the differences in simulated inorganic aerosol concentrations and the hygroscopic growth efficiency (affected by varied relative humidity). These differences in composition and AOD suggest that future models can be improved by including new heterogeneous or aqueous pathways for sulfate and nitrate formation under hazy conditions, a secondary organic aerosol (SOA) formation chemical mechanism with new volatile organic compound (VOCs) precursors, yield data and approaches, and a more detailed evaluation of the dependence of aerosol optical properties on size distribution and mixing state. It was also found that using the ensemble mean of the models produced the best prediction skill. While this has been shown for other conditions (for example, the prediction of high-ozone events in the US (McKeen et al., 2005)), this is to our knowledge the first time it has been shown for heavy haze events.

In this study, winter precipitation variability associated with the El Niño-Southern Oscillation (ENSO) over the Korean Peninsula was investigated using a 5-pentad running mean data because significant correlation pattern cannot be revealed using seasonal-mean data. It was found a considerably significant positive correlation between Niño3 sea-surface temperature and precipitation during early winter (from Mid-November to early-December), when the correlation coefficient is close to 0.8 in early-December; the correlation is distinctively weakened during late winter. It is demonstrated that such sudden intraseasonal change in relation to ENSO is associated with the presence of anticyclonic flow over the Kuroshio extension region (Kuroshio anticyclone). In early winter, there is strong southerly wind over the Korean Peninsula, which is induced by the Philippine Sea anticyclone and Kuroshio anticyclone. However, in January, although the Philippine Sea anticyclone develops further, the Kuroshio anticyclone suddenly disappears; as a result, the impact of ENSO is considerably weakened over the Korean Peninsula. These results indicate that the Kuroshio anticyclone during El Niño peak phase plays a critical role by strongly affecting Northeast Asia climate, including the Korean Peninsula. In addition, it is also found that there are distinctive interdecadal changes of the relationship between ENSO and precipitation over the Korean Peninsula. In particular, the strong correlation in early winter is clearer in the recent 30 years than that in the previous period of 1950-1979. © 2013 Springer-Verlag Berlin Heidelberg

Nitrogen dioxide (NO 2 ) columns observed from space have been useful in detecting the increase of nitrogen oxides (NO x ) emissions in East Asia, particularly China, coinciding with rapid economic growth during the past several decades. NO 2 columns retrieved above a particular location reflect a combination of local NO x emissions and transported NO x from upwind sources. In this study, we demonstrate the transport of NO x emitted in East Asia using satellite and surface in situ measurements and Lagrangian particle dispersion model simulations. Enhanced satellite NO 2 columns in the Yellow Sea (between China and South Korea) and the East Sea (between South Korea and Japan), and different seasonal variations of NO 2 in China, North and South Korea, and Japan, suggest the importance of NO x transport in understanding the local NO x budget. Lagrangian transport model simulations with tracers of different chemical lifetimes identify source-receptor relationships that explain high NO 2 over the oceans and springtime peaks in Korea and Japan, with China being the most likely source region. Our results have important implications for studies using satellite NO 2 retrievals to derive NO x emissions at local scales in regions adjacent to large sources, such as in East Asia, Europe, and the Eastern U.S.