Abstract
Abstract. This study presents an analysis of both MOZAIC profiles above Frankfurt and Lagrangian dispersion model simulations for the 2003 European heat wave. The comparison of MOZAIC measurements in summer 2003 with the 11-year MOZAIC climatology reflects strong temperature anomalies (exceeding 4°C) throughout the lower troposphere. Higher positive anomalies of temperature and negative anomalies of both wind speed and relative humidity are found for the period defined here as the heat wave (2–14 August 2003), compared to the periods before (16–31 July 2003) and after (16–31 August 2003) the heat wave. In addition, Lagrangian model simulations in backward mode indicate the suppressed long-range transport in the mid- to lower troposphere and the enhanced southern origin of air masses for all tropospheric levels during the heat wave. Ozone and carbon monoxide also present strong anomalies (both ~+40 ppbv) during the heat wave, with a maximum vertical extension reaching 6 km altitude around 11 August 2003. Pollution in the planetary boundary layer (PBL) is enhanced during the day, with ozone mixing ratios two times higher than climatological values. This is due to a combination of factors, such as high temperature and radiation, stagnation of air masses and weak dry deposition, which favour the accumulation of ozone precursors and the build-up of ozone. A negligible role of a stratospheric-origin ozone tracer has been found for the lower troposphere in this study. From 29 July to 15 August 2003 forest fires burnt around 0.3×106 ha in Portugal and added to atmospheric pollution in Europe. Layers with enhanced CO and NOy mixing ratios, advected from Portugal, were crossed by the MOZAIC aircraft in the free troposphere over Frankfurt. A series of forward and backward Lagrangian model simulations have been performed to investigate the origin of anomalies during the whole heat wave. European anthropogenic emissions present the strongest contribution to the measured CO levels in the lower troposphere (near 30%). This source is followed by Portuguese forest fires which affect the lower troposphere after 6 August 2003 and even the PBL around 10 August 2003. The averaged biomass burning contribution reaches 35% during the affected period. Anthropogenic CO of North American origin only marginally influences CO levels over Europe during that period.
Highlights
Summer 2003 was one of the hottest in the history of Western Europe, with surface temperature exceeding by 2.4◦C the average surface temperature reported for the 1901–1995 period (Luterbacher et al, 2004)
Anomalous anticyclonic conditions during summer led to an increase in the monthly mean daily
The objective of this paper is to investigate for the first time the vertical extension and the origins of pollutants during the 2003 heat wave with a set of 162 profiles of ozone, carbon monoxide and relative humidity performed from 16 July to 31 August 2003 by 3 MOZAIC airliners over Frankfurt (Measurements of OZone, water vapour, carbon monoxide and nitrogen oxides by Airbus In-service airCraft, http:// mozaic.aero.obs-mip.fr/web/), (Marenco et al, 1998)
Summary
Summer 2003 was one of the hottest in the history of Western Europe, with surface temperature exceeding by 2.4◦C the average surface temperature reported for the 1901–1995 period (Luterbacher et al, 2004). Temperatures reached exceptional high levels, and both the number of consecutive days during which temperatures exceeded the seasonal average and the spatial extent of the heat wave episode have never been reported before (Trigo et al, 2005). In August, the temperature increase peaked during the first two weeks due to a strong amplification of Rossby waves that reinforced the pre-existing anticyclone over Europe (Grazzini et al, 2003; Trigo et al, 2005). Anomalous anticyclonic conditions during summer led to an increase in the monthly mean daily
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