Dataset contains supplementary information (model inputs and/or outputs and literature values) for Section 4.1 (idealized acidity calculations), Section 4.2 (box model calculations of pH for ambient conditions), Section 7.1 (observed aerosol pH values), Section 7.2 (observed cloud pH values), and Section 8.1 (CMAQ hemispheric predictions). This dataset is associated with the following publication: Pye, H., A. Nenes, B. Alexander, A. Ault, M. Barth, S. Clegg, J. Collett, K. Fahey, C. Hennigan, H. Herrmann, M. Kanakidou, J. Kelly, I. Ku, V.F. McNeill, N. Riemer, T. Schaefer, G. Shi, A. Tilgner, J. Walker, T. Wang, R. Weber, J. Xing, R. Zaveri, and A. Zuend. The Acidity of Atmospheric Particles and Clouds. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 20(8): 4809–4888, (2020).

The effect of acidity and relative humidity on bulk isoprene aerosol parameters has been investigated in several studies, however few measurements have been conducted on individual aerosol compounds. The focus of this study has been the examination of the effect of acidity and relative humidity on secondary organic aerosol (SOA) chemical composition from isoprene photooxidation in the presence of nitrogen oxide (NOx). A detailed characterization of SOA at the molecular level was also investigated. Experiments were conducted in a 14.5 m3 smog chamber operated in flow mode. Based on a detailed analysis of mass spectra obtained from gas chromatography-mass spectrometry of silylated derivatives in electron impact and chemical ionization modes, and ultra-high performance liquid chromatography/electrospray ionization/time-of-flight high resolution mass spectrometry, and collision-induced dissociation in the negative ionization modes, we characterized not only typical isoprene products, but also new oxygenated compounds. A series of nitroxy-organosulfates (OS) were tentatively identified on the basis of high resolution mass spectra. Under acidic conditions, the major identified compounds include 2-methyltetrols (2MT), 2-methylglyceric acid (2MGA) and 2MT-OS. Other products identified include epoxydiols, mono- and dicarboxylic acids, other organic sulfates, and nitroxy- and nitrosoxy-OS. The contribution of SOA products from isoprene oxidation to PM2.5 was investigated by analysing ambient aerosol collected at rural sites in Poland. Methyltetrols, 2MGA and several organosulfates and nitroxy-OS were detected in both the field and laboratory samples. The influence of relative humidity on SOA formation was modest in non-acidic seed experiments, and stronger under acidic seed aerosol. Total secondary organic carbon decreased with increasing relative humidity under both acidic and non-acidic conditions. While the yields of some of the specific organic compounds decreased with increasing relative humidity others varied in an indeterminate manner from changes in the relative humidity. This dataset is associated with the following publication: Nestorowicz, K., M. Jaoui, K. Rudzinski, M. Lewandowski, T. Kleindienst, G. Spolnik, W. Danikiewicz, and R. Szmigielski. Chemical Composition of Isoprene SOA Under Acidic and Non-Acidic Conditions: Effect of Relative Humidity. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 18(4): 18101-18121, (2018).

The effect of acidity and relative humidity on bulk isoprene aerosol parameters has been investigated in several studies, however few measurements have been conducted on individual aerosol compounds. The focus of this study has been the examination of the effect of acidity and relative humidity on secondary organic aerosol (SOA) chemical composition from isoprene photooxidation in the presence of nitrogen oxide (NOx). A detailed characterization of SOA at the molecular level was also investigated. Experiments were conducted in a 14.5 m3 smog chamber operated in flow mode. Based on a detailed analysis of mass spectra obtained from gas chromatography-mass spectrometry of silylated derivatives in electron impact and chemical ionization modes, and ultra-high performance liquid chromatography/electrospray ionization/time-of-flight high resolution mass spectrometry, and collision-induced dissociation in the negative ionization modes, we characterized not only typical isoprene products, but also new oxygenated compounds. A series of nitroxy-organosulfates (OS) were tentatively identified on the basis of high resolution mass spectra. Under acidic conditions, the major identified compounds include 2-methyltetrols (2MT), 2-methylglyceric acid (2MGA) and 2MT-OS. Other products identified include epoxydiols, mono- and dicarboxylic acids, other organic sulfates, and nitroxy- and nitrosoxy-OS. The contribution of SOA products from isoprene oxidation to PM2.5 was investigated by analysing ambient aerosol collected at rural sites in Poland. Methyltetrols, 2MGA and several organosulfates and nitroxy-OS were detected in both the field and laboratory samples. The influence of relative humidity on SOA formation was modest in non-acidic seed experiments, and stronger under acidic seed aerosol. Total secondary organic carbon decreased with increasing relative humidity under both acidic and non-acidic conditions. While the yields of some of the specific organic compounds decreased with increasing relative humidity others varied in an indeterminate manner from changes in the relative humidity. This dataset is associated with the following publication: Nestorowicz, K., M. Jaoui, K. Rudzinski, M. Lewandowski, T. Kleindienst, G. Spolnik, W. Danikiewicz, and R. Szmigielski. Chemical Composition of Isoprene SOA Under Acidic and Non-Acidic Conditions: Effect of Relative Humidity. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 18(4): 18101-18121, (2018).

This dataset contains data presented in the figures of the paper "On the implications of aerosol liquid water and phase separation for organic aerosol mass" published in Atmospheric Chemistry and Physics. It also links to the data archive of field observations. This dataset is associated with the following publication: Pye, H., B. Murphy, L. Xu, N. Ng, A. Carlton, H. Guo, R. Weber, P. Vasilakos, W. Appel, S. Budisulistiorini, J. Surratt, A. Nenes, W. Hu, J. Jimenez, G. saacman-VanWertz, P. Misztal, and A. Goldstein. On the implications of aerosol liquid water and phase separation for organic aerosol mass. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 17: 343-369, (2017).

These data are a part of Multi-Decadal Sulfur Dioxide (SO2) Climatology from Satellite Instruments (MEaSUREs-12-0022 project). Version 2 of the global catalogue of emissions from large SO2 point sources combines data from the Ozone Monitoring Instrument (OMI) on NASA's EOS Aura spacecraft, the Ozone Mapping and Profiler Suite (OMPS) on the NASA-NOAA Suomi National Polar-orbiting Partnership (SNPP), and the TROPOspheric Monitoring Instrument (TROPOMI) on the ESA/Copernicus Sentinel-5 Precursor (S-5P) spacecraft.The catalogue MSAQSO2L4 file contains the site coordinates, source type, country, source name, annual SO2 emissions, annual emission uncertainties, and the number of satellite pixels in the fitting area for three satellite instruments as well as for their weighted average.The emission estimates are based on operational version 2 OMI and OMPS Principal Component Analysis (PCA) retrieval algorithm SO2 slant column density (SCD) data (Li et al., 2020) as well as on new TROPOMI Covariance-Based Retrieval Algorithm (COBRA) SCD data (Theys et al., 2021). A single time-independent site-specific Air-Mass Factor (AMF) value for each site was calculated (McLinden et al., 2014) and applied consistently to each satellite SCD dataset to derive SO2 vertical column densities (VCDs=SCDs/AMFs). The emission estimate method is based on a fit of satellite VCDs to an empirical plume model developed to describe the SO2 spatial distribution near emission point sources. The plume model assumes that the SO2 concentrations emitted from a point source decline exponentially with distance and that they are affected by turbulent diffusion that can be described by a two-dimensional (2D) exponentially modified Gaussian function. The total SO2 mass is derived from the fit and the annual emission rate is calculated as the ratio between the total mass and the prescribed SO2 lifetime.

SAGE2_AEROSOL_O3_NO2_H2O_BINARY_V7.0 is the Stratospheric Aerosol and Gas Experiment (SAGE) II Version 7.0 Aerosol, O3, NO2 and H2O Profiles data set in the SAGE II native binary format. It contains aerosol extinction, ozone, nitrogen dioxide, and water vapor profiles. Data collection for this data set is complete. Over the long 21-year mission, the spacecraft experienced episodic anomalies in the power system. These anomalies were usually followed by a period where the occultation events were of limited duration. These so-called short events may have had an insufficient number of exoatmospheric scans of the solar disk precluding an accurate determination of the solar limb darkening curve and the scan mirror relative reflectivity. In version 7.0, these events, a total of 4900, were dropped so that the data users no longer needed to filter out those events. Further, there were approximately 150 events that did not complete processing in earlier versions that were successfully processed in this version. The net result was that there were more usable profiles in v7.0 than in previous versions. SAGE II was a payload installed aboard the Earth Radiation Budget Satellite (ERBS), which was launched on October 5, 1984, from NASA Space Shuttle Flight 41-G. The SAGE II instrument was a multi-channel spectral radiometer that measured the attenuation of solar radiation at seven wavelengths as they passed through the Earth's atmosphere during the spacecraft's sunrise and sunset events. In one day’s time, the ERBS spacecraft encountered approximately fifteen sunrise and fifteen sunset events. The SAGE II instrument captured solar radiation data for each event. The data span was a vertical distance from about 140 kilometers to the horizon or a cloud top. The ground-track slew distance during data capture varied directly with the duration of the event. Event duration varied with the beta angle of the event - the larger the absolute beta angle, the longer the event. SAGE II continued the SAGE measurements of stratospheric ozone from 1984-2005. After nearly 21 years, the SAGE II Instrument on the ERBS platform was powered off on 22 August, 2005.

Data and CMAQ code associated with manuscript, "Updated in-cloud secondary aerosol production in the Northern Hemisphere predicted by the Community Multiscale Air Quality modeling system ". This dataset is associated with the following publication: Fahey, K., N. Sareen, A.M. Carlton, and B. Hutzell. Updated in-cloud secondary aerosol production in the Northern Hemisphere predicted by the Community Multiscale Air Quality modeling system. ACS Earth and Space Chemistry. American Chemical Society, Washington, DC, USA, 9(5): 1043–1059, (2025).

The TROPESS Chemical Reanalysis Surface Aerosol SO4 2-Hourly 3-dimensional Product contains surface concentrations of sulfate aerosols. The data are part of the Tropospheric Chemical Reanalysis v2 (TCR-2) for the period 2005-2021. TCR-2 uses JPL's Multi-mOdel Multi-cOnstituent Chemical (MOMO-Chem) data assimilation framework that simultaneously optimizes both concentrations and emissions of multiple species from multiple satellite sensors.The data files are written in the netCDF version 4 file format, and each file contains a year of data at 2-hourly resolution, and a spatial resolution of 1.125 x 1.125 degrees. The principal investigator for the TCR-2 data is Miyazaki, Kazuyuki.

The TROPESS Chemical Reanalysis Surface Aerosol SO4 Monthly 3-dimensional Product contains vertical concentrations of sulfate aerosols. The data are part of the Tropospheric Chemical Reanalysis v2 (TCR-2) for the period 2005-2021. TCR-2 uses JPL's Multi-mOdel Multi-cOnstituent Chemical (MOMO-Chem) data assimilation framework that simultaneously optimizes both concentrations and emissions of multiple species from multiple satellite sensors.The data files are written in the netCDF version 4 file format, and each file contains a year of data at monthly resolution, and a spatial resolution of 1.125 x 1.125 degrees at 27 pressure levels between 1000 and 60 hPa. The principal investigator for the TCR-2 data is Miyazaki, Kazuyuki.

These data are a part of Multi-Decadal Sulfur Dioxide (SO2) Climatology from Satellite Instruments (MEaSUREs-12-0022 project). Version 2 of the global catalogue of emissions from large SO2 point sources combines data from the Ozone Monitoring Instrument (OMI) on NASA's EOS Aura spacecraft, the Ozone Mapping and Profiler Suite (OMPS) on the NASA-NOAA Suomi National Polar-orbiting Partnership (SNPP), and the TROPOspheric Monitoring Instrument (TROPOMI) on the ESA/Copernicus Sentinel-5 Precursor (S-5P) spacecraft. The catalogue MSAQSO2L4 file contains the site coordinates, source type, country, source name, annual SO2 emissions, annual emission uncertainties, and the number of satellite pixels in the fitting area for three satellite instruments as well as for their weighted average. The emission estimates are based on operational version 2 OMI and OMPS Principal Component Analysis (PCA) retrieval algorithm SO2 slant column density (SCD) data (Li et al., 2020) as well as on new TROPOMI Covariance-Based Retrieval Algorithm (COBRA) SCD data (Theys et al., 2021). A single time-independent site-specific Air-Mass Factor (AMF) value for each site was calculated (McLinden et al., 2014) and applied consistently to each satellite SCD dataset to derive SO2 vertical column densities (VCDs=SCDs/AMFs). The emission estimate method is based on a fit of satellite VCDs to an empirical plume model developed to describe the SO2 spatial distribution near emission point sources. The plume model assumes that the SO2 concentrations emitted from a point source decline exponentially with distance and that they are affected by turbulent diffusion that can be described by a two-dimensional (2D) exponentially modified Gaussian function. The total SO2 mass is derived from the fit and the annual emission rate is calculated as the ratio between the total mass and the prescribed SO2 lifetime.