09 Nov 2022
09 Nov 2022
Status: this preprint is open for discussion.

Data fusion uncertainty-enabled methods to map street-scale hourly NO2 in Barcelona city: a case study with CALIOPE-Urban v1.0

Alvaro Criado1, Jan Mateu Armengol1, Hervé Petetin1, Daniel Rodríguez-Rey1, Jaime Benavides1,3, Marc Guevara1, Carlos Pérez García-Pando1,2, Albert Soret1, and Oriol Jorba1 Alvaro Criado et al.
  • 1Barcelona Supercomputing Center, Barcelona, Spain
  • 2ICREA, Catalan Institution for Research and Advanced Studies, Barcelona, Spain
  • 3Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA

Abstract. Comprehensive monitoring of NO2 exceedances is imperative for protecting human health, especially in trafficked urban areas. However, accurate spatial characterization of exceedances is challenging due to the typically low density of air quality monitoring stations and the inherent uncertainties of urban air quality models. We study how observational data from different sources and time scales can be combined with a dispersion air quality model to obtain bias-corrected NO2 hourly maps at the street scale. We present a kriging-based data-fusion workflow that merges a dispersion model output with continuous hourly observations, and uses a machine-learning-based Land Use Regression (LUR) model constrained with past short intensive passive dosimeter campaigns observations. While the hourly observations allow to bias-adjust the temporal variability of the dispersion model, the microscale-LUR model adds information on the NO2 spatial patterns. Our method includes uncertainty calculation based on the estimated error variance of the Universal Kriging technique, which is subsequently used to produce urban maps of probability of exceeding the 200 µg /m3 hourly and the 40 µg /m3 NO2 annual average limits. We assess the statistical performance of this approach in the city of Barcelona for the year 2019. Our results show that simply merging the monitoring stations with the model output already significantly increases the correlation coefficient (r) by +29 % and decreases the Root Mean Square Error (RMSE) by -32 %. When adding the time-invariant LUR model in the data-fusion workflow, the improvement is even more remarkable: +46 % and -48 % for the r and RMSE, respectively. Our work highlights the usefulness of high-resolution spatial information in data-fusion methods to estimate exceedances at the street scale better.

Alvaro Criado et al.

Status: open (until 04 Jan 2023)

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  • RC1: 'Comment on egusphere-2022-1147', Anonymous Referee #1, 05 Dec 2022 reply

Alvaro Criado et al.

Alvaro Criado et al.


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Short summary
The goal of this work is to derive and evaluate a general statistical post-processing tool specifically designed for the street scale that can be applied to any urban air quality system. Our data-fusion methodology corrects NO2 fields based on continuous hourly observations and experimental campaigns. This study able us to obtain exceedance probability maps of air quality standards. In 2019, 13 % of the Barcelona area had a 70 % or higher probability of exceeding the annual legal NO2 limit.