The impact of differences in large-scale circulation output from climate models on the regional modeling of ozone and PM
- ISSN: 16807316
- DOI: 10.5194/acp-12-9441-2012
Climate change may have an impact on air qual- ity (ozone, particulate matter) due to the strong dependency of air quality on meteorology. The effect is often studied us- ing a global climate model (GCM) to produce meteorolog- ical fields that are subsequently used by chemical transport models. However, climate models themselves are subject to large uncertainties and fail to reproduce the present-day cli- mate adequately. The present study illustrates the impact of these uncertainties on air quality. To this end, output from the SRES-A1B constraint transient runs with two GCMs, i.e. ECHAM5 and MIROC-hires, has been dynamically down- scaled with the regional climate model RACMO2 and used to force a constant emission run with the chemistry transport model LOTOS-EUROS in a one-way coupled run covering the period 1970–2060. Results from the two climate simulations have been com- pared with a RACMO2-LOTOS-EUROS (RLE) simulation forced by the ERA-Interim reanalysis for the period 1989– 2009. Both RLE ECHAMand RLE MIROCshowed consid- erable deviations from RLE ERA for daily maximum tem- perature, precipitation and wind speed. Moreover, sign and magnitude of these deviations depended on the region. The differences in average present-day concentrations between the simulations were equal to (RLE MIROC) or even larger than (RLE ECHAM) the differences in concentrations be- tween present-day and future climate (2041–2060). The cli- mate simulations agreed on a future increase in average sum- mer ozone daily maximum concentrations of 5–10 µgm−3 in parts of Southern Europe and a smaller increase in West- ern and Central Europe. Annual average PM10 concentra- tions increased 0.5–1.0 µgm−3 in North-West Europe and the the Po Valley, but these numbers are rather uncertain: over- all, changes for PM10 were small, both positive and nega- tive changes were found, and for many locations the two cli- mate runs did not agree on the sign of the change. This il- lustrates that results from individual climate runs can at best indicate tendencies and should therefore be interpreted with great care.