the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Global Source-Receptor-Relationship Database for Integrated Tropospheric Ozone Observations from Multiplatform Datasets in Western North America during 1994–2021
Abstract. Long-term atmospheric ozone observations in Western North America (WNA) provide essential data for assessing tropospheric ozone trends. Backward atmospheric simulations based on these observations establish the source-receptor relationships (SRRs) to improve our understanding of the factors driving ozone trends across different regions, time periods, and atmospheric layers. In this study, we integrated 28 years of ozone data (1994–2021) from ozonesondes, lidar, commercial aircraft, and aircraft campaigns across WNA, spanning the upper atmospheric boundary layer, free troposphere, and upper troposphere (i.e., 900 to 300 hPa). We reconciled the multiplatform datasets using a data fusion framework to generate 553,608 gridded ozone receptors. For each receptor, we use the FLEXible PARTicle (FLEXPART) dispersion model, driven by ERA5 reanalysis data, to achieve the SRRs calculations, providing global simulations at high temporal (hourly) and spatial (1° x 1°) resolution from the surface up to 20 km above ground level. This SRR database retains detailed information for each receptor, including the gridded ozone value product, which enables user to illustrate and identify source contributions to various subsets of ozone observations in the troposphere above WNA over nearly 3 decades at different vertical layers and temporal scales, such as diurnal, daily, seasonal, intra-annual, and decadal. More generally, the calculated SRRs are applicable to any study looking to evaluate origins of airmasses reaching WNA. As such, this database can support source contribution analyses for other atmospheric components observed over WNA, if other co-located observations have been made at the spatial and temporal scales defined for some or all of the gridded ozone receptors used here.
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RC1: 'Comment on essd-2024-571', Anonymous Referee #1, 29 Apr 2025
General comments
This paper describes a source-receptor relationships (SRRs) database using Flexpart dispersion model with ERA5 reanalysis data. The objective is to provide a data base usable for ozone observations studies over Western North America.
The methodology is pertinent and very well described in chapter 3, with suitable product illustration in chapter 4, with sensitivity illustrations with altitude and seasonal. The chapter 5 shows a possible application to NOx emissions influence on O3 photochemical production.
The text and the figures are excellent quality and I have no additional comment before publication.
Minor comments (typos)
Line 53: replace “western” by “Western”
Line 76: add “.” after “ECMWF model”
Citation: https://doi.org/10.5194/essd-2024-571-RC1 -
RC2: 'Comment on essd-2024-571', Anonymous Referee #2, 20 Jul 2025
The paper submitted by Cui et al. describe a data base of Source-Receptor-Relationships (SSR) corresponding to tropospheric ozone observations in Western North America. SSR retrieval is based on FLEXPART model V.10 following an approach similar to Cooper et al. 2010 but using more up to date meteorological analysis (ERA 5) and a better seasonal coverage. A data fusion technique has been implemented using the work of Chang et al. (2023) but applied to a more comprehensive ozone data base including new vertical levels and all observations available in Western North America (ozonesonde, lidar, aircraft).
The paper is a brief presentation of the SRR data base with some illustrations of its potential usefulness. More elaborated results will be described in future papers. The main results of the present paper are (i) a description of the FLEXPART model configuration in section 3, (ii) two illustrations of the spatial distributions of SRR for low or high ozone data set in section 4, (iii) while section 5 describes how SRR can be combined with source distributions of ozone precursor. In section 5 the example of the sensitivity to NOx tropical lightning source has been chosen.
I recommend publication of this paper as it is a useful addition to future papers using this SRR data base. However I believe that a short paragraph is missing in section 3 in order to describe differences between this new SSR and the Cooper et al. (2010) 1994-2008 spring time analysis. Such a new short paragraph would be a nice way to discuss the benefits of using ERA 5 and a more comprehensive ozone observation data set.
Since long range transport analysis is often viewed as a key component to understand how stratosphere-troposphere exchanges (STE) control ozone increase in the free troposphere, the authors might consider an additional illustration to show how the new SRR could help to address this issue.
Detailed remarks
line 78. CTMs are indeed more complex tools but we can address different question related, especially the complex inetraction between dynamical an photochemical processes
line 130 Indeed the measurement error might be minor considering the large data set considered in this work, however Fig. 1 shows also a change an significant increase of data sampling after 2004. I wonder how this feature will be accounted for in the SRR data analysis.
line 236 Fig. 2 only show that long range transport change when considering different altitude levels in WNA. Such a very genral picture is difficult to discuss detailed questions as the sensitivity to aircraft emission, biomass burning or STE.
line 250 Fig. 3 Is indeed a good illustration to describe the potential of the new data base.
Fig. 4: I believe Fig. 4 shows the seasonal sensitivity for the whole tropospheric column, this should be clarified
Fig. 5: I am not sure how to interpret the trend in the sum of the residence time. More residence time in the 3-13 km vertical range during the 21th century for the air masses with high ozone ?
Citation: https://doi.org/10.5194/essd-2024-571-RC2
Data sets
Global Source-Receptor-Relationship Database for Western North America Tropospheric Ozone Observations during 1994-2021 using FLEXPART-ERA5 Yu Yan Cui https://doi.org/10.5281/zenodo.14227019
Gridded ozone receptors over western North America from 900hPa to 300hPa during 1994-2021 Kai-Lan Chang and Owen R. Cooper https://doi.org/10.5281/zenodo.14227019
Post-Processed Global Source-Receptor-Relationship Database for Western North America Tropospheric Ozone Observations during 1994-2021 Ju-Mee Ryoo, Laura T. Iraci, Matthew S. Johnson https://doi.org/10.5281/zenodo.14227019
Interactive computing environment
Global Source-Receptor-Relationship Database for Western North America Tropospheric Ozone Observations during 1994-2021 using FLEXPART-ERA5 Yu Yan Cui https://doi.org/10.5281/zenodo.14227019
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