The sensitivity of aerosol in Europe to two different emission inventories and temporal distribution of emissions

[摘要] The sensitivity to two different emission inventories, injection altitudeand temporal variations of anthropogenic emissions in aerosol modelling isstudied, using the two way nested global transport chemistry model TM5focussing on Europe in June and December 2000. The simulations of gas andaerosol concentrations and aerosol optical depth (AOD) with the EMEP andAEROCOM emission inventories are compared with EMEP gas and aerosol surfacebased measurements, AERONET sun photometers retrievals and MODIS satellitedata.

For the aerosol precursor gases SO₂ and NO_x in both months themodel results calculated with the EMEP inventory agree better (overestimatedby a factor 1.3 for both SO₂ and NO_x) with the EMEP measurementsthan the simulation with the AEROCOM inventory (overestimated by a factor2.4 and 1.9, respectively).

Besides the differences in total emissions between the two inventories, animportant role is also played by the vertical distribution of SO₂ andNO_x emissions in understanding the differences between the EMEP andAEROCOM inventories.

In December NO_x and SO₂ from both simulations agree within 50%with observations.

In June SO₄⁼ evaluated with the EMEP emission inventory agreesslightly better with surface observations than the AEROCOM simulation,whereas in December the use of both inventories results in an underestimateof SO4 with a factor 2. Nitrate aerosol measured in summer is not reliable,however in December nitrate aerosol calculations with the EMEP and AEROCOMemissions agree with 30%, and 60%, respectively with the filtermeasurements. Differences are caused by the total emissions and the temporaldistribution of the aerosol precursor gases NO_x and NH₃. Despitethese differences, we show that the column integrated AOD is less sensitiveto the underlying emission inventories. Calculated AOD values with bothemission inventories underestimate the observed AERONET AOD values by 20–30%, whereas a case study using MODIS data shows a high spatialagreement.

Our evaluation of the role of temporal distribution of anthropogenicemissions on aerosol calculations shows that the daily and weekly temporaldistributions of the emissions are only important for NO_x, NH₃ andaerosol nitrate. However, for all aerosol species SO₄⁼,NH₄⁺, POM, BC, as well as for AOD, the seasonal temporalvariations used in the emission inventory are important. Our study shows thevalue of including at least seasonal information on anthropogenic emissions,although from a comparison with a range of measurements it is oftendifficult to firmly identify the superiority of specific emissioninventories, since other modelling uncertainties, e.g. related to transport,aerosol removal, water uptake, and model resolution, play a dominant role.

[学科分类] 大气科学