I-Chun Tsai

Atmospheric iron deposition in the northwestern Pacific Ocean and its adjacent marginal seas: The importance of coal burning

This study applied a regional air quality model, incorporated with an emission module, to quantitatively differentiate the atmospheric iron sources originating from lithogenic dusts or coal-burning fly ashes deposited in the Northwestern Pacific Ocean and its marginal seas. Particular attention was paid to the high iron content of fly ashes emitted from steel and iron plants burning coals. Using the year 2007 as an example, the modeling results exhibit large seasonal variations in iron deposition, with highest deposition fluxes occurred during spring and autumn, which are comparable to the seasonal fluctuation of chlorophyll a concentrations estimated by satellite images in the oceanic regions. Fly ash from coal burning accounted for 7.2% of the total iron deposited over the northwestern Pacific Ocean and 15% of that over the northern South China Sea. After considering the difference of iron solubility in the aerosols, anthropogenic aerosol associated with coal burning would be the major bioavailable iron source in the surface water of the oceanic regions.

Potential impacts of electric vehicles on air quality in Taiwan.

The prospective impacts of electric vehicle (EV) penetration on the air quality in Taiwan were evaluated using an air quality model with the assumption of an ambitious replacement of current light-duty vehicles under different power generation scenarios. With full EV penetration (i.e., the replacement of all light-duty vehicles), CO, VOCs, NOx and PM2.5 emissions in Taiwan from a fleet of 20.6 million vehicles would be reduced by 1500, 165, 33.9 and 7.2Ggyr(-1), respectively, while electric sector NOx and SO2 emissions would be increased by up to 20.3 and 12.9Ggyr(-1), respectively, if the electricity to power EVs were provided by thermal power plants. The net impacts of these emission changes would be to reduce the annual mean surface concentrations of CO, VOCs, NOx and PM2.5 by about 260, 11.3, 3.3ppb and 2.1μgm(-3), respectively, but to increase SO2 by 0.1ppb. Larger reductions tend to occur at time and place of higher ambient concentrations and during high pollution events. Greater benefits would clearly be attained if clean energy sources were fully encouraged. EV penetration would also reduce the mean peak-time surface O3 concentrations by up to 7ppb across Taiwan with the exception of the center of metropolitan Taipei where the concentration increased by <2ppb. Furthermore, full EV penetration would reduce annual days of O3 pollution episodes by ~40% and PM2.5 pollution episodes by 6-10%. Our findings offer important insights into the air quality impacts of EV and can provide useful information for potential mitigation actions.

Dynamic Feedback of Aerosol Effects on the East Asian Summer Monsoon

AbstractThe influence of present-day anthropogenic aerosols on the summer monsoon over the East Asia region was simulated using the Community Earth System Model coupled with a slab ocean model. The simulations revealed significant radiative forcing from anthropogenic aerosols and associated changes in clouds over East Asia and the northwestern Pacific; however, their spatial patterns differed from the exhibited surface temperature and precipitation responses. Two major dynamic feedback mechanisms were identified to explain such discrepancies. The wind–evaporation–sea surface temperature (WES) feedback, triggered by an initial cooling over the midlatitude sea surface, induced an equatorward expansion of ocean cooling through strengthened trade winds. The sea surface cooling excited a meridional wave pattern similar to the Pacific–Japan teleconnection pattern. Although the aerosol effect generally caused weakening in summer monsoon strength and regional precipitation over East Asia, precipitation increases ...

METHANE-NITROGEN BINARY NUCLEATION: A NEW MICROPHYSICAL MECHANISM FOR CLOUD FORMATION IN TITAN'S ATMOSPHERE

It is known that clouds are present in the troposphere of Titan; however, their formation mechanism, particle size, and chemical composition remain poorly understood. In this study, a two-component (CH{sub 4} and N{sub 2}) bin-microphysics model is developed and applied to simulate cloud formation in the troposphere of Titan. A new process, binary nucleation of particles from CH{sub 4} and N{sub 2} gases, is considered. The model is validated and calibrated by recent laboratory experiments that synthesize particle formation in Titan-like environments. Our model simulations show that cloud layers can be formed at about 20 km with a particle size ranging from one to several hundred {mu}m and number concentration 10{sup -2} to over 100 cm{sup -3} depending on the strength of the vertical updraft. The particles are formed by binary nucleation and grow via the condensation of both CH{sub 4} and N{sub 2} gases, with their N{sub 2} mole fraction varying from 30% in the condensation growth stage. The locally occurring CH{sub 4}-N{sub 2} binary nucleation mechanism is strong and could potentially be more important than the falling condensation nuclei mechanism assumed in many current models.

Numerical investigation of the coagulation mixing between dust and hygroscopic aerosol particles and its impacts

A statistical-numerical aerosol parameterization was incorporated into the Community Multiscale Air Quality modeling system to study the coagulation mixing process focusing on a dust storm event that occurred over East Asia. Simulation results show that the coagulation mixing process tends to decrease aerosol mass, surface area, and number concentrations over the dust source areas. Over the downwind oceanic areas, aerosol concentrations generally increased due to enhanced sedimentation as particles became larger upon coagulation. The mixture process can reduce the overall single-scattering albedo by up to 10% as a result of enhanced core with shell absorption by dust and reduction in the number of scattering particles. The enhanced dry deposition speed also altered the vertical distribution. In addition, the ability of aerosol particles to serve as cloud condensation nuclei (CCN) increased from around 107u2009m−3 to above 109u2009m−3 over downwind areas because a large amount of mineral dust particles became effective CCN with solute coating, except over the highly polluted areas where multiple collections of hygroscopic particles by dust in effect reduced CCN number. This CCN effect is much stronger for coagulation mixing than by the uptake of sulfuric acid gas on dust, although the nitric acid gas uptake was not investigated. The ability of dust particles to serve as ice nuclei may decrease or increase at low or high subzero temperatures, respectively, due to the switching from deposition nucleation to immersion freezing or haze freezing.

Climate–Chemistry Interaction: Future Tropospheric Ozone and Aerosols

Publisher Summary nThe radiative heating and cooling of the atmosphere is affected by perturbations of CO2, primary aerosols, and chemically active greenhouse compounds (CH4, N2O, CFCs), and by secondary compounds (tropospheric ozone, sulfate, and organic aerosols) that are formed in the atmosphere through a variety of chemical and physical processes. While the concentrations of these secondary compounds are dominated by the surface emissions of their gas phase precursors, they are also closely coupled to meteorological parameters: temperature, wind, and the hydrological cycle (moisture, precipitation, and clouds), and to solar radiation (photo-dissociation). Therefore, climate changes due to global warming from anthropogenic greenhouse additions may perturb atmospheric concentrations of chemically active climate compounds and thus the oxidation capacity of the atmosphere, providing feedback to the climate system. As the climatic states and surface precursor emissions exhibit distinctively different regional characteristics, this climate–chemistry interactions will play an important role in future climate changes that will disturb different areas differently.The radiative heating and cooling of the atmosphere is affected by perturbations of CO 2 , primary aerosols, and chemically-active greenhouse compounds (CH 4 , N 2 O, CFCs), and by secondary compounds (tropospheric ozone, sulfate, and organic aerosols) that are formed in the atmosphere through a variety of chemical and physical processes. While the concentrations of these secondary compounds are dominated by the surface emissions of their gas phase precursors, they are also closely coupled to meteorological parameters: temperature, wind, and the hydrological cycle (moisture, precipitation, and clouds), and to solar radiation (photo-dissociation). Therefore, climate changes due to global warming from anthropogenic greenhouse additions may perturb atmospheric concentrations of chemically-active climate compounds and thus the oxidation capacity of the atmosphere, providing feedback to the climate system. As the climatic states and surface precursor emissions exhibit distinctively different regional characteristics, these climate–chemistry interactions will play an important role in future climate changes that will disturb different areas differently.

Chapter 13 – Climate–Chemistry Interaction: Future Tropospheric Ozone and Aerosols

Publisher Summary nThe radiative heating and cooling of the atmosphere is affected by perturbations of CO2, primary aerosols, and chemically active greenhouse compounds (CH4, N2O, CFCs), and by secondary compounds (tropospheric ozone, sulfate, and organic aerosols) that are formed in the atmosphere through a variety of chemical and physical processes. While the concentrations of these secondary compounds are dominated by the surface emissions of their gas phase precursors, they are also closely coupled to meteorological parameters: temperature, wind, and the hydrological cycle (moisture, precipitation, and clouds), and to solar radiation (photo-dissociation). Therefore, climate changes due to global warming from anthropogenic greenhouse additions may perturb atmospheric concentrations of chemically active climate compounds and thus the oxidation capacity of the atmosphere, providing feedback to the climate system. As the climatic states and surface precursor emissions exhibit distinctively different regional characteristics, this climate–chemistry interactions will play an important role in future climate changes that will disturb different areas differently.The radiative heating and cooling of the atmosphere is affected by perturbations of CO 2 , primary aerosols, and chemically-active greenhouse compounds (CH 4 , N 2 O, CFCs), and by secondary compounds (tropospheric ozone, sulfate, and organic aerosols) that are formed in the atmosphere through a variety of chemical and physical processes. While the concentrations of these secondary compounds are dominated by the surface emissions of their gas phase precursors, they are also closely coupled to meteorological parameters: temperature, wind, and the hydrological cycle (moisture, precipitation, and clouds), and to solar radiation (photo-dissociation). Therefore, climate changes due to global warming from anthropogenic greenhouse additions may perturb atmospheric concentrations of chemically-active climate compounds and thus the oxidation capacity of the atmosphere, providing feedback to the climate system. As the climatic states and surface precursor emissions exhibit distinctively different regional characteristics, these climate–chemistry interactions will play an important role in future climate changes that will disturb different areas differently.

Climate–Chemistry Interaction

Publisher Summary nThe radiative heating and cooling of the atmosphere is affected by perturbations of CO2, primary aerosols, and chemically active greenhouse compounds (CH4, N2O, CFCs), and by secondary compounds (tropospheric ozone, sulfate, and organic aerosols) that are formed in the atmosphere through a variety of chemical and physical processes. While the concentrations of these secondary compounds are dominated by the surface emissions of their gas phase precursors, they are also closely coupled to meteorological parameters: temperature, wind, and the hydrological cycle (moisture, precipitation, and clouds), and to solar radiation (photo-dissociation). Therefore, climate changes due to global warming from anthropogenic greenhouse additions may perturb atmospheric concentrations of chemically active climate compounds and thus the oxidation capacity of the atmosphere, providing feedback to the climate system. As the climatic states and surface precursor emissions exhibit distinctively different regional characteristics, this climate–chemistry interactions will play an important role in future climate changes that will disturb different areas differently.The radiative heating and cooling of the atmosphere is affected by perturbations of CO 2 , primary aerosols, and chemically-active greenhouse compounds (CH 4 , N 2 O, CFCs), and by secondary compounds (tropospheric ozone, sulfate, and organic aerosols) that are formed in the atmosphere through a variety of chemical and physical processes. While the concentrations of these secondary compounds are dominated by the surface emissions of their gas phase precursors, they are also closely coupled to meteorological parameters: temperature, wind, and the hydrological cycle (moisture, precipitation, and clouds), and to solar radiation (photo-dissociation). Therefore, climate changes due to global warming from anthropogenic greenhouse additions may perturb atmospheric concentrations of chemically-active climate compounds and thus the oxidation capacity of the atmosphere, providing feedback to the climate system. As the climatic states and surface precursor emissions exhibit distinctively different regional characteristics, these climate–chemistry interactions will play an important role in future climate changes that will disturb different areas differently.