Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high-time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models.

Organic aerosol (OA) data acquired by the Aerosol Mass Spectrometer (AMS) in 37 field campaigns were deconvolved into hydrocarbon‐like OA (HOA) and several types of oxygenated OA (OOA) components. HOA has been linked to primary combustion emissions (mainly from fossil fuel) and other primary sources such as meat cooking. OOA is ubiquitous in various atmospheric environments, on average accounting for 64%, 83% and 95% of the total OA in urban, urban downwind, and rural/remote sites, respectively. A case study analysis of a rural site shows that the OOA concentration is much greater than the advected HOA, indicating that HOA oxidation is not an important source of OOA, and that OOA increases are mainly due to SOA. Most global models lack an explicit representation of SOA which may lead to significant biases in the magnitude, spatial and temporal distributions of OA, and in aerosol hygroscopic properties.

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea in Hawaii. A team of scientists from Japan, Taiwan and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg 2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg 2 in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg 2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.

[1] Aerosol chemical composition and gaseous species were measured at Cape Hedo, Okinawa, Japan (CHO), during the ABC/EAREX project period in March 2005, using high-time-resolution instruments including an Aerodyne quadrupole aerosol mass spectrometer (Q-AMS), a tapered element oscillating microbalance (TEOM), and gas monitors in order to investigate the transport and subsequent chemical transformation of aerosol in the east Asian region. Sulfate was the dominant species in fine aerosol mode and the average concentration of ammonium, sulfate and organics was 1.25, 6.37 and 2.16 mg m À3 , respectively. The sulfate concentration observed at CHO in 2005 was about 1.5-2 times higher than that in 1994. For the majority of high-sulfate observations, the air mass was transported from the central east Chinese region (between Shanghai and the Shandong Peninsula). Sulfate transport was intermittent and strongly correlated with the passage of synoptic-scale high-/low-pressure systems. Chemical components and their concentration showed significant change on 17-18 March, which is accounted for by the change in air mass origin and the synoptic-scale weather system. In addition, it is suggested that the difference of air quality at the air mass origin reflects the chemical composition at CHO. The high sulfate concentration required heterogeneous conversion of SO 2 to sulfate at a rate of 2.0% h À1 . A pronounced signal at m/z = 44 confirmed that organic compounds were oxidized.