Representativeness of the IAGOS airborne measurements in the lower troposphere

H Petetin,G Athier,P Nedelec,B Sauvage,M Steinbacher,V Thouret,R Blot,M Jeoffrion,F Gheusi,D Boulanger,J.-M Cousin,H Clark,Detlev Helmig,Frank Flocke

doi:10.1525/elementa.280

Abstract

In the framework of the In Service Aircraft for Global Observing System (IAGOS) program, airborne in-situ O3 and CO measurements are performed routinely using in-service aircraft, providing vertical profiles from the surface to about 10–12 km. Due to the specificity of IAGOS measurements (measurements around busy international airports), uncertainties exist on their representativeness in the lower troposphere as they may be impacted by emissions related to airport activities and/or other aircraft. In this study, we thus investigate how the IAGOS measurements in the lower troposphere compare with nearby surface stations (from the local Air Quality monitoring network (AQN)) and more distant regional surface stations (from the Global Atmospheric Watch (GAW) network). The study focuses on Frankfurt but some results at other European airports (Vienna, Paris) are also discussed. Results indicate that the IAGOS observations close to the surface do not appear to be strongly impacted by local emissions related to airport activities. In terms of mixing ratio distribution, seasonal variations and trends, the CO and O3 mixing ratios measured by IAGOS in the first few hundred metres above the surface have similar characteristics to the mixing ratios measured at surrounding urban background stations. Higher in altitude, both the difference with data from the local AQN and the consistency with the GAW regional stations are higher, which indicates a larger representativeness of the IAGOS data. Despite few quantitative differences with Frankfurt, consistent results are obtained in the two other cities Vienna and Paris. Based on 11 years of data (2002–2012), this study thus demonstrates that IAGOS observations in the lowest troposphere can be used as a complement to surface stations to study the air quality in/around the agglomeration, providing important information on the vertical distribution of pollution.

Highlights

In-situ observations are essential to improve our knowledge on the chemical composition of the atmosphere and its evolution with time, and to validate models and satellite observations
In terms of mixing ratio distribution, seasonal variations and trends, the carbon monoxide (CO) and O3 mixing ratios measured by In Service Aircraft for Global Observing System (IAGOS) in the first few hundred metres above the surface have similar characteristics to the mixing ratios measured at surrounding urban background stations
Based on 11 years of data (2002–2012), this study demonstrates that IAGOS observations in the lowest troposphere can be used as a complement to surface stations to study the air quality in/around the agglomeration, providing important information on the vertical distribution of pollution

Summary

Introduction

In-situ observations are essential to improve our knowledge on the chemical composition of the atmosphere and its evolution with time, and to validate models and satellite observations. While the network of surface stations has considerably expanded over the last decades ( not in all regions of the world), in-situ observations still remain much sparser in altitude. Besides dedicated aircraft research campaigns that provide a detailed view of the chemical composition of the atmosphere but with a limited spatio-temporal coverage, routine in-situ measurements still essentially rely on radiosondes and commercial aircraft. Routine in-situ airborne observations of chemical species not restricted to O3 – e.g. carbon monoxide (CO), nitrogen oxides (NOx), carbon dioxide (CO2), methane (CH4) – rely on only a few programs conducting airborne measurements using in-service aircraft since the 1990s. Among the programs still on-going, the oldest is the CONTRAIL (Comprehensive Observation Network for TRace gases by AIrLiner) program, within which greenhouse gases (CO2, CH4, N2O, SF6) measurements have been performed since 1993 using Boeing aircraft operated by Japan Airlines (Machida et al, 2008)

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