Atmospheric Chemistry of the East Asian Northwest Pacific Region

Abstract

The East Asian Continental Rim region is characterized by high and rapidly growing anthropogenic emissions of NO_X, SO₂, hydrocarbons, and other air pollutants due to its high and growing population density and, in some regions, intensive industrial development. Emissions of NO_X and SO₂ from the East Asian region have been growing at a rate of about 4% per year in the last decade, which is in marked contrast to the trends in Western Europe and North America where those emissions have been stabilized or started to decline after 1980. The main focus of the IGAC-APARE (East Asian/North Pacific Regional Experiment) is to understand the increasing human impact on the chemical processes occurring in the atmosphere of the East Asian Northwest Pacific Ocean. Scientists from Pacific Rim countries (China, Taiwan, Hong Kong, Japan, South Korea and Russia) as well as the U.S. and Australia have joined to steer the APARE activity.

The first intensive APARE field study was completed in September-October 1991, by the cooperative leadership of the U.S. National Aeronautics and Space Administration (NASA) and the Japanese National Institute of Environmental Studies (NIES). NASA’s initiative, named PEM-West (Pacific Exploratory Mission), consisted of airborne measurements using the NASA DC-8 and ground-based studies. The DC-8 flew across the Pacific ocean and intensive data flights were conducted from operational bases established in Japan, Hong Kong and Guam. Data were obtained over a wide range of selected geographical areas and meteorological conditions. NIES organized a study called PEACAMPOT (Perturbatioxn by East Asian Continental Air Mass to the Pacific Oceanic Troposphere), which consisted of airborne measurements using a CESSNA-404 and ground-based studies. The CESSNA-404 sampled the air in a selected area of the East China Sea, Yellow Sea and Japan Sea. Ground stations were situated on the eastern coast of China, and in Japan, Korea, Taiwan and Hawaii, as well as on several remote Pacific islands, and scientists from these involved countries joined the study.

The PEM-West measurements provided an extensive characterization of air masses over the western North Pacific Ocean including clean oceanic air, continental outflow, stratospheric air, equatorial marine air and southern hemispherical marine air. The major greenhouse gases, ozone and its precursors, sulfur species, and continental and marine aerosols were measured, and the airborne remote lidar system provided a two-dimensional mapping of the atmospheric ozone and aerosol distributions along the entire set of flight tracks. Unique results were obtained concerning the transport of trace gases in a major typhoon. The PEACAMPOT measurements characterized the air masses near the continental rim of East Asia.