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Regional responses of surface ozone in Europe to the location of high-latitude blocks and subtropical ridges

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Ordoñez García, Carlos and Barriopedro Cepero, David and García Herrera, Ricardo and Sousa, Pedro M. and Schnell, Jordan L. (2017) Regional responses of surface ozone in Europe to the location of high-latitude blocks and subtropical ridges. Atmospheric chemistry and physics, 17 (4). pp. 3111-3131. ISSN 1680-7316

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Official URL: http://dx.doi.org/10.5194/acp-17-3111-2017




Abstract

This paper analyses for the first time the impact of high-latitude blocks and subtropical ridges on near-surface ozone (O-3) in Europe during a 15-year period. For this purpose, a catalogue of blocks and ridges over the Euro-Atlantic region is used together with a gridded dataset of maximum daily 8 h running average ozone (MDA8 O-3) covering the period 1998-2012. The response of ozone to the location of blocks and ridges with centres in three longitudinal sectors (Atlantic, ATL, 30-0 degrees W; European, EUR, 0-30 degrees E; Russian, RUS, 30-60 degrees E) is examined. The impact of blocks on ozone is regionally and seasonally dependent. In particular, blocks within the EUR sector yield positive ozone anomalies of similar to 5-10 ppb over large parts of central Europe in spring and northern Europe in summer. Over 20 and 30% of the days with blocks in that sector register exceedances of the 90th percentile of the seasonal ozone distribution at many European locations during spring and summer, respectively. The impacts of ridges during those seasons are subtle and more sensitive to their specific location, although they can trigger ozone anomalies above 10 ppb in northern Italy and the surrounding countries in summer, eventually exceeding European air quality (AQ) targets. During winter, surface ozone in the north-west of Europe presents completely opposite responses to blocks and ridges. The anticyclonic circulation associated with winter EUR blocking, and to a lesser extent with ATL blocking, yields negative ozone anomalies between 5 and 10 ppb over the UK, northern France and the Benelux. Conversely, the enhanced zonal flow around 50-60 degrees N during the occurrence of ATL ridges favours the arrival of background air masses from the Atlantic and the ventilation of the boundary layer, producing positive ozone anomalies of similar to 5 ppb in an area spanning from the British Isles to the northern half of Germany. We also show that multiple linear models on the seasonal frequency of occurrence of these synoptic patterns can explain a considerable fraction of the interannual variability in some winter and summer ozone statistics (mean levels and number of exceedances of the 90th percentile) over some regions of western Europe. Thus, this work provides the first quantitative assessments of the remarkable but distinct impacts that the anticyclonic circulation and the diversion of the zonal flow associated with blocks and ridges exert on surface ozone in Europe. The findings reported here can be exploited in the future to evaluate the modelled responses of ozone to circulation changes within chemical transport models (CTMs) and chemistry-climate models (CCMs).


Item Type:Article
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© Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 License. Carlos Ordoñez acknowledges funding from the Ramón y Cajal Programme of the Spanish Ministerio de Economía y Competitividad under grant RYC-2014-15036.

Uncontrolled Keywords:Northern-hemisphere blocking; Southeast United-States; Air-quality; Tropospheric-ozone; Atmospheric circulation; Atlantic oscillation; Climate-change; Heat-wave; Po basin; Mediterranean basin
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:42842
Deposited On:25 May 2017 08:20
Last Modified:10 Dec 2018 15:04

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