Recent laboratory studies indicated that a photo‐induced heterogeneous reaction of ozone on the surface of aerosol containing humic like substances (HULIS) has the potential to affect the ozone ...budget in biomass burning plumes. To evaluate atmospheric significance of such heterogeneous light induced ozone loss, this process has been taken into account in the simulation of the extreme air pollution episode in the Moscow region during the 2010 mega fire event in western Russia. Results of the numerical experiments performed with the CHIMERE chemistry transport model indicate that photo induced removal of ozone could lead to significant (reaching several tens of percent) episodic decrease of the ozone concentration. The simulations also show that while wildfires provide reactive surface for the considered reaction, they strongly inhibit the photo‐induced heterogeneous ozone loss by attenuating actinic fluxes through the “shielding” aerosol effect. The present results are calling for additional experimental and modelling studies.
Key Points
Photo induced ozone loss on biomass burning aerosol is a significant process
Aerosol is a self‐inhibiting agent of the heterogeneous light induced ozone loss
Uncertainties in reactivity of biomass burning aerosol call for new studies
Ammonia (NH3), whose main source in the troposphere is agriculture, is an important gaseous precursor of atmospheric particulate matter (PM). We derived daily ammonia emissions using NH3 total ...columns measured from the Infrared Atmospheric Sounding Interferometer (IASI) on board Metop‐A, at a relatively high spatial resolution (grid cell of 0.5° × 0.5°). During the European spring haze episodes of 24–31 March 2012 and 8–15 March 2014, IASI reveals NH3 total column magnitudes highlighting higher NH3 emissions over central Europe (especially over Germany, Czech Republic, and eastern France) from the ones provided by the European reference European Monitoring and Evaluation Programme inventory. These ammonia emissions exhibit in addition a large day‐to‐day variability, certainly due to spreading practices. The increase of NH3 emissions in the model, that reaches +300% locally, leads to an increase of both NH3 and PM2.5 surface concentrations and allows for a better comparison with independent measurements (in terms of bias, root‐mean‐square error, and correlation). This study suggests that there are good prospects for better quantifying NH3 emissions by atmospheric inversions.
Key Points
Strong potential of IASI for deducing NH3 daily emissions
High NH3 emissions revealed over central Europe
Strong impact of NH3 emissions on pollution particle formation
First partial tropospheric ozone columns (0–6 km) derived from radiances observed by the IASI instrument aboard the MetOp‐A platform over Europe during summer 2007 are presented. They were retrieved ...using an altitude‐dependent regularization method. Comparison with measurements from balloon sondes shows excellent agreement. Space‐borne observations show large lower tropospheric ozone amounts over South‐Eastern Europe during the heat wave period, which are also displayed by simulations with a regional chemistry‐transport model CHIMERE.
This study describes and evaluates the newly developed European scale Eulerian chemistry transport model CHIMERE-continental. The model is designed for seasonal simulations and real time forecasts ...without the use of super-computers. For the purpose of model evaluation simulated ozone mixing ratios for the period between 1 May 1998 and 30 September 1998 are compared to observational data from 115 European surface sites. In order to facilitate the interpretation of future forecasts a statistic is established to estimate the reliability of a simulated pollution level. Besides this, the comparison is done by means of time series, scatter plots, a spectral analysis and the calculation of RMS-errors and biases of the model results corresponding to each observation site. It turns out that the mean RMS-error of the simulated daily maximum ozone mixing ratio for the sites considered
a priori as well suited for a model comparison is about
10
ppb
. For the same period but a reduced number of sites observed concentrations of NO
2 and ethene are compared to simulated values. Difficulties encountered with the representativeness of observations when trying to evaluate a mesoscale air pollution model are discussed.
Aerosol modeling is a challenging scientific problem aimed at improving our knowledge in the many complex processes involved in multiphase chemistry and transport. Correct simulations of aerosols are ...also required in order to elaborate particle emission reduction strategies. The CHIMERE chemistry transport model (Atmos. Environ. 35 (2001) 6277) has been improved to account for particle transport, formation, deposition at the European scale. The aerosol model accounts both for inorganic
(NO
3
−
,
SO
4
2−
,
NH
4
+)
and organic species of primary or secondary origin. Secondary organic aerosols from biogenic and anthropogenic gas precursors are partitioned into gas and particulate phases through a temperature dependent partition coefficient. The modeling approach is presented in this paper with preliminary simulation results over Europe. Comparisons with available data at background stations give acceptable results on PM
10, with correlation coefficients usually exceeding 0.5 and normalized errors in the 30–80% range in many regions. However, results on sulfate, nitrate and ammonium species display less correct error statistics. Comparisons on sulfate concentrations give normalized errors in the range 30–80% in summer and less correct in winter. Temporal correlation coefficients usually range from 0.30 to 0.70. Nitrate concentrations are better simulated during winter than during summer. Difficulties in simulating heterogeneous and aqueous phase processes could explain model deficiencies. Moreover, temperature dependence of gas/particle partitioning processes for nitrate, ammonium and secondary organic species could mainly explain the seasonal variability of biases. Model deficiencies are observed in Southern countries, certainly due to natural dust emissions and resuspended particles. Finally, sea salts seems to have a quite significant influence on error statistics in coastal areas.
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