Description: We validate the Ozone Monitoring Instrument (OMI) ozone-profile (PROFOZ) product from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against ozonesonde observations. We also evaluate the effects of OMI Row anomaly (RA) on the retrieval by dividing the data set into before and after the occurrence of serious OMI RA, i.e., pre-RA (2004–2008) and post-RA (2009–2014). The retrieval shows good agreement with ozonesondes in the tropics and mid-latitudes and for pressure 〈 ~ 50 hPa in the high latitudes. It demonstrates clear improvement over the a priori down to the lower troposphere in the tropics and down to an average of ~ 550 (300) hPa at middle (high latitudes). In the tropics and mid-latitudes, the profile mean biases (MBs) are less than 6 %, and the standard deviations (SDs) range from 5–10 % for pressure 〈 ~ 50 hPa to less than 18 % (27 %) in the tropics (mid-latitudes) for pressure 〉 ~ 50 hPa after applying OMI averaging kernels to ozonesonde data. The MBs of the stratospheric ozone column (SOC) are within 2 % with SDs of 〈 5 % and the MBs of the tropospheric ozone column (TOC) are within 6 % with SDs of 15 %. In the high latitudes, the profile MBs are within 10 % with SDs of 5–15 % for pressure 〈 ~ 50 hPa, but increase to 30 % with SDs as great as 40 % for pressure 〉 ~ 50 hPa. The SOC MBs increase up to 3 % with SDs as great as 6 % and the TOC SDs increase up to 30 %. The comparison generally degrades at larger solar-zenith angles (SZA) due to weaker signals and additional sources of error, leading to worse performance at high latitudes and during the mid-latitude winter. Agreement also degrades with increasing cloudiness for pressure 〉 ~ 100 hPa and varies with cross-track position, especially with large MBs and SDs at extreme off-nadir positions. In the tropics and mid-latitudes, the post-RA comparison is considerably worse with larger SDs reaching 2 % in the stratosphere and 8 % in the troposphere and up to 6 % in TOC. There are systematic differences that vary with latitude compared to the pre-RA comparison. The retrieval comparison demonstrates good long-term stability during the pre-RA period, but exhibits a statistically significant trend of 0.14–0.7 %/year for pressure 〈 ~ 80 hPa, 0.7 DU/year in SOC and −0.33 DU/year in TOC during the post-RA period. The spatiotemporal variation of retrieval performance suggests the need to improve OMI’s radiometric calibration especially during the post-RA period to maintain the long-term stability and reduce the latitude/season/SZA and cross-track dependence of retrieval quality.

Description: Samples were collected with a Sigma-2 sampler (Waza et al., 2019) on top of the tower of the Meteorological Observatory of Izaña between 08 July 2005 and 08 August 2005. The geographical coordinates are N 28.3094° and W 16.4992°, height is approximately 2,390 m above sea level. Samples were only collected during Saharan dust advection (Kandler et al., 2007). Samples were subject to automated scanning electron microscopy with coupled X-ray analysis (Kandler et al., 2018). This data set contains the results of a sample re-analysis with more modern instrumentation in 2017. Each data file is one sample, an overview with meta data is given in the sample list file. Please refer to the description files for more details.

Description: In support of the first Tropospheric Ozone Assessment Report (TOAR) a relational database of global surface ozone observations has been developed and populated with hourly measurement data and enhanced metadata. A comprehensive suite of ozone metrics products including standard statistics, health and vegetation impact metrics, and trend information, are made available through a common data portal and a web interface. These data form the basis of the TOAR analyses focusing on human health, vegetation, and climate relevant ozone issues, which are part of this special feature. By combining the data from almost 10,000 measurement sites around the world with global metadata information, new analyses of surface ozone have become possible, such as the first globally consistent characterisations of measurement sites as either urban or rural/remote. Exploitation of these global metadata allow for new insights into the global distribution, and seasonal and long-term changes of tropospheric ozone. Cooperation among many data centers and individual researchers worldwide made it possible to build the world's largest collection of in-situ hourly surface ozone data covering the period from 1970 to 2015. Considerable effort was made to harmonize and synthesize data formats and metadata information from various networks and individual data submissions. Extensive quality control was applied to identify questionable and erroneous data, including changes in apparent instrument offsets or calibrations. Such data were excluded from TOAR data products. Limitations of a posteriori data quality assurance are discussed. As a result of the work presented here, global coverage of surface ozone data has been significantly extended. Yet, large gaps remain in the surface observation network both in terms of regions without monitoring, and in terms of regions that have monitoring programs but no public access to the data archive. Therefore future improvements to the database will require not only improved data harmonization, but also expanded data sharing and increased monitoring in data-sparse regions.