This dataset contains NO, NO2 and NOx mixing ratio measurements using the commercially available Thermo 42C chemiluminescence monitor. Measurements were made at the Indian Institute of Technology Delhi (IIT-Delhi), India. Mixing ratios are reported in parts per billion (ppb). The stationary inlet was located on the roof of a 5-storey building at Block IV, Indian Institute of Technology Delhi campus. The data were collected over three measurement periods (i) winter: 12/01/2018 - 13/02/2018, (ii) pre-monsoon: 26/04/2018 - 05/06/2018 and (iii) post-monsoon: 13/10/2018 - 10/11/2018, by the University of Birmingham. These data were collected as part of the ASAP-Delhi project as part of the Atmospheric Pollution and Human Health in an Indian Megacity (APHH) programme.

Sentinel 5 Precursor (S5P) was launched on the 13th of October 2017 carrying the TROPOspheric Monitoring Instrument (TROPOMI). These data products provide geolocated total, tropospheric, or stratospheric Nitrogen dioxide concentrations. The TROPOMI NO2 data products pose an improvement over previous NO2 data sets, particularly in their unprecedented spatial resolution (7×3.5 km2), but also in the separation of the stratospheric and tropospheric contributions of the retrieved slant columns, and in the calculation of the air-mass factors used to convert slant to total columns. Nitrogen dioxide (NO2) and nitrogen oxide (NO) together are usually referred to as nitrogen oxides (NOx = NO + NO2). They are important trace gases in the Earth’s atmosphere, present in both the troposphere and the stratosphere. They enter the atmosphere as a result of anthropogenic activities (notably fossil fuel combustion and biomass burning) and natural processes (such as microbiological processes in soils, wildfires and lightning). During the daytime, i.e. in the presence of sunlight, a photochemical cycle involving ozone (O3) converts NO into NO2 (and vice versa) on a timescale of minutes, so that NO2 is a robust measure for concentrations of nitrogen oxides. Tropospheric and stratospheric concentrations of NO2 are monitored all over the world by a variety of instruments either ground-based, in-situ (balloon, aircraft), or satellite-based each with its own specific advantages.

This dataset contains O3, CO, NO, NO2, NOy and SO2 concentration measurements from the University of York's Thermo 49i O3 analyser, Aero Laser 5002 CO analyser, Air Quality Design (AQD) NOx analyser, Thermo 42c Trace Level NOx analyser with AQD NOy converter and a Thermo 43i SO2 analyser. These instruments were located at the Indira Gandi Delhi Technical University for Women (IGDTUW). The instruments sampled from a common sample line, initially at 7 m above ground level, then were moved to 35 m above ground on the 5th of November 2018. The data were collected as part of the DelhiFlux project part of Air Pollution & Human Health in a Developing Indian Megacity (APHH-India) programme.

This dataset contains ozone, NO, NO2, NOX, SO2 and PM2.5 air quality and meteorological measurements from two campaigns undertaken in Guangzhou, China in 2019. NO, NO2 and NOX were measured by Chemiluminescence with a Thermo scientific 42i-TL. Ozone were measured via UV with a Thermo scientific 49i. PM2.5 were measured by a continuous particulate monitor (BAM-1020, Met One instruments Inc). SO2 were measured via Pulsed fluorescence with a Thermo scientific 43i-TLE. This data were collected as part of the NERC project Investigating the large source of particulate mass from nitrophenols observed in Beijing during winter haze events (NITRO-PM).

This dataset represents a collation of surface measurements of nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO) and isoprene (C5H8) from publicly available data sets (of hourly, daily and monthly resolutions), for the aim of improved evaluation of surface ozone in global atmospheric chemistry models. Measurements begin in 1980 running through to 2015. The data comes in a range of formats, with a plethora of associated data quality issues, requiring substantial cleaning before being able to be utilised for model assessment. 1,033,463,750 measurements from 16,996 sites are processed through numerous data quality checks, resulting in 76,413,458 observations from 1607 sites of appropriate quality (with the majority of excluded observations due to urban influence). Observations are heavily weighted towards North America and Europe, with generally sparse coverage over the rest of the globe (with the exception of CO). See documentation for more details. Data is provided as multiple globally gridded output files, each consisting of a series of metrics designed to reflect the distributions of the observed ozone precursor species, allowing fair and easy comparison with global models. Metrics include the moments of the distribution (i.e. mean, temporal standard deviation, skewness and kurtosis) and percentiles. A total of 80 different netCDF-4 files are produced, with metrics calculated in multiple temporal (monthly and annual) and spatial configurations (8 different resolutions), for each different species. The format of the output netCDF-4 files is designed to be consistent with the related dataset which compiled surface ozone observations (v2.7).