Isoprene, Methyl Vinyl Ketone and Methacrolein from TROICA-12 Measurements and WRF-CHEM and GEOS-CHEM Simulations in the Far East Region

Spatial and temporal distributions of isoprene and its oxidation products, methyl vinyl ketone and methacrolein in the Far East region of Russia were investigated. The measurement data were obtained from a mobile laboratory, which moved along the Trans-Siberian railway and from WRF-CHEM (Weather Research and Forecasting Chemical Model) and GEOS-CHEM (Goddard Earth Observing System Chemical Model) simulations. During the simulations, the RACM-MIM and MOZART mechanisms, included in the mesoscale WRF-CHEM model, as well as the Caltech Isoprene Scheme (CIS), built in the global GEOS-CHEM model, have been used. We found that the temporal distribution of the measured isoprene is in good agreement with the simulations. The measured isoprene, methyl vinyl ketone (MVK) and methacrolein (MACR) concentrations demonstrate pronounced diurnal variations. The correlation between the measured isoprene and MVK + MACR was good (R ~ 0.60–0.86). However, the simulated correlation between MVK + MACR and isoprene is very low, with the data for the night-time and daytime values varying. The simulated MVK + MACR to isoprene ratio, in comparison with the experimental result, has pronounced diurnal variations. During twilight and the night-time, the simulated MVK + MACR to isoprene ratio is more than 10. We propose that, due to the validity of the kinetic equations only in the homogeneous system, all chemical and transport (CTM) models, based on these kinetic equations, are not able to show an adequate simulation at night in the weak mixing atmosphere, when the atmospheric structure becomes heterogeneous. At moderate latitudes, we recommend the use of the turbulent Damköhler number and the Kolmogorov Damköhler numbers, which characterize the limits of CTM applicability, as the quality flags at the air quality forecast simulations

CHANGES IN TRENDS OF ATMOSPHERIC COMPOSITION OVER URBAN AND BACKGROUND REGIONS OF EURASIA: ESTIMATES BASED ON SPECTROSCOPIC OBSERVATIONS

The analysis of the CO and CH4 total column (TC) as well as aerosol optical depth (AOD) data in urban and background regions of Eurasia for different seasons and periods from 1998 to 2016 years is presented. Trends estimates based on longterm spectroscopic datasets of OIAP RAS (Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences) for stations Moscow, Zvenigorod (ZSS, Moscow province), Zotino (ZOTTO, Central Siberia), Beijing (joint site of OIAP RAS and IAP CAS (Institute of Atmospheric Physics, Chinese Academy of Sciences)), SPbSU stations Peterhof and NDACC stations located in Eurasia were compared between themselves and with similar assessments obtained from satellite data. Significant decrease of anthropogenic CO in megacities Moscow (3.5±2.2%/yr) and Beijing (1.4±1.4%/yr) in autumn months of 1998−2016 were found according ground-based spectroscopic observations. In spite of total anthropogenic CO emissions decrease (for Europe and China) and absence of growth of wild-fires emissions in 2007−2016 we found that CO TC in background regions of Northern Eurasia has stabilized or increased in summer and autumn months of 2007−2016. Decrease of AOD over Central and Southern Europe and over China (1−5%/ yr) was observed after 2007. Since 2007 an increase in CH4 TC trends over Northern Europe as well as for tropical belt of Eurasia has been obtained. Analysis of satellite observations AIRS v6 of CO and CH4 TC and MODIS AOD data confirmed the ground-based estimates of trends