the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Technical note: An interactive dashboard to facilitate quality control of in-situ atmospheric composition measurements
Abstract. In-situ measurements of trace gases are crucial for monitoring changes in the atmosphere's composition and understanding the underlying processes that drive them. For over three decades, the Global Atmosphere Watch (GAW) programme of the World Meteorological Organization (WMO) has coordinated a network of surface monitoring stations and facilities with the goal of providing high-quality atmospheric composition measurements worldwide. One of the critical challenges towards this goal is the spatially unbalanced availability of high-quality time series, and the lack of near-realtime quality control (QC) procedures that would allow the prompt detection of unreliable data. Here, we describe an interactive dashboard designed for GAW station operators, but which may be of much wider use, that is able to flag anomalous values in near-realtime or historical data. The dashboard combines three distinct algorithms that identify anomalous measurements: (i) an outlier detection based on the Subsequence Local Outlier Factor (Sub-LOF) method, (ii) a comparison with numerical forecasts coupled with a machine learning model, and (iii) a Seasonal Autoregressive Integrated Moving Average (SARIMA) regression model. The application, called GAW-QC, can process measurements of methane (CH4), carbon monoxide (CO), carbon dioxide (CO2), and ozone (O3) at hourly resolution, offering multiple statistical and visual aids to help users to identify problematic data. By enhancing QC capabilities, GAW-QC contributes to the GAW programme's goal of providing reliable atmospheric measurements worldwide.
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Status: open (until 05 Apr 2025)
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RC1: 'Comment on egusphere-2024-3556', Anonymous Referee #1, 27 Jan 2025
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This manuscript introduced an interactive dashboard tool for detecting anomalous measurements which may help identifying measurement quality issue. This tool is based on three independent algorithms. The algorithms were discussed in the manuscript with application in actual data. The authors correctly pointed out that the anomalous points may or may not be related to measurement problems and the measurement problems should be determined by the instrument scientists or operators. This reviewer believes this tool may help improve measurement quality, but the manuscript did not adequately discuss the effectiveness of this tool. One obvious issue is that not all measurement quality problems are shown as anomalies. The authors should revise the manuscript after considering the comments below.
Major Comments:
- The manuscript primarily focused on discussions about ways to detect anomalous data points. As stated by the authors, the anomalies may not be related to the measurement quality issues. In fact, many unexpected changes in data can be related to swift meteorological condition changes and/or “accidental” emission sources. In general data should not be flagged unless potential specific instrument and/or sampling issues are identified. In this context, it would be helpful for the non-data science readers to see the effectiveness of this tool to identify the measurement problems. This reviewer would like to see the percentage of the identified anomalous data that can be linked to measurement problems and what kind of measurement problems were identified using this tool. This reviewer believes it is an important factor for readers to evaluate the usefulness of the tool if they understand the underlying processes associated with the detected anomalous data.
- It is not widely accepted that the model products can be used to judge measurement problems. This is especially problematic for comparison with ground site observations as the models do not capture local scale meteorology and small emission sources, while both can be reflected in the observations at a given time and location. This may be a more serious problem when dealing with more reactive species.
- The actual measurement problems are often discovered by examine the relationship between variables observed at the same location and time. For example, the stratospheric intrusion case presented in the manuscript should be characterized by higher ozone levels and lower water vapor, in addition to low CO levels. Looking an CO times alone with the model output cannot be considered as convincing… The model can often have a phase shift. It would be much more useful if the tool can take advantage of the simultaneous measurements at a given site.
Specific Comments:
- Table 1.: The authors should explain why and how total column CH4/CO/O3, black carbon, and water vapor would help explain surface observations. This reviewer believes that the readers deserve some physical explanations.
- Line 92: “exceeds 5%”, how sensitive is this choice? Also, why only the “highest sampling height” is selected? Is there often a sharp gradient observed?
- Sub-LOF: the authors should provide more description on the general principle of this algorithm.
- Section 3.2. The authors should discuss the performance of the CAMS model and the difference between the forecast mode and reanalysis mode.
- Line 167: “based on expert knowledge” is not an acceptable justification. The choice of the variables should be explained and justified based on atmospheric sciences.
- Section 3.4.1.: The authors should clearly define true positive, false positive, and false negative. Some examples should be provided to explain these concepts.
- Figure 3: what do the circles represent?
Citation: https://doi.org/10.5194/egusphere-2024-3556-RC1
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