Gas Chemistry Mechanisms

1. INSTITUTE OF ATMOSPHERIC SCIENCES AND CLIMATE ACCENT SYMPOSIUM Urbino, September 12th-16th, 2005 DEVELOPMENT AND PRELIMINARY RESULTS OF A LIMITED AREA ATMOSPHERE-CHEMISTRY MODEL: BOLCHEM M. D’Isidoro(1),S. Fuzzi (1), A. Maurizi (1), F. Monforti (2), M. Mircea (1), F. Tampieri (1), M. G. VIllani (1) & G. Zanini (2) (1) Istitute of Atmospheric Sciences and Climate, ISAC-CNR, Bologna, Italy (www.isac.cnr.it) (2) ENEA PROT-INN Section, Bologna, Italy Radiative transfer model Meteorological Model BOLAM (Buzzi et al., 2003) Gas Chemistry (SAPRC90 or CB-IV) Initial and boundary conditions Emissions Dry Deposition 1 Vd = + + Rb Ra Rc DISCUSSION AND FUTURE DEVELOPMENTS • xxxx. • yyyy • zzzz Gas Chemistry Mechanisms OVERVIEW Air quality forecast is controlled by a number of factors: emissions, chemistry, microphysics and meteorology are equally important in determining the evolution oh the chemical composition of the atmosphere. Here we present the first step of development of the model BOLCHEM, developed for regional air quality forecast. The first results obtained for a high ozone episode over Italy are shown, comparing the model results obtained with two different chemical mechanisms (SAPRC-90 and CB-IV) and ground-based measurements. GENERAL SCHEME OF BOLCHEM SAPRC90 CB-IV 131 reactions 35 species (10 fast, 25 slow) 85 reactions 30 species (11 fast, 19 slow) u,v, T, P, q Photolysis Rates HNO3 HONO HNO4 CO HO2H OOH PAN PPN HCHO CCHO RCHO RNO3 MGLY AFG2 SO2 ETHE OLE1 OLE2 OLE3 OLE4 ALK1 ALK2 ARO1 ARO2 O3 NO NO2 NO3 N2O5 HO2 RO2 CCO3 C2CO3 MEK CRES PNA HONO HNO3 PAN H2O2 MEOH PAR ETH OLE TOL XYL CO FORM ALD2 MGLY OPEN ETOH O3 NO NO2 NO3 N2O5 C2O3 XO2 CRO CRES HO2 ROR ISOP NTR BOLAM Model • Hydrostatic model based on primitive equations with u, v, , q, ps as dependent variables + 5 microphysical variables: cloud ice, cloud water, rain , snow, hail/graupel; • Rotated Arakawa C grid; σ vertical coordinate (non uniform, staggered Lorenz grid); • WAF (Weighted Average Flux) 3-d advection scheme coupled with semi-Lagrangian advection of hydrometeors; • Radiation: infrared and solar, interacting with clouds (Ritter & Geleyn and ECMWF RRTM - Morcrette); • Vertical diffusion (surface layer and PBL parameterization) depending on the Richardson number; DRY DEPOSITION SCHEME The dry deposition scheme follows a resistance analogy approach (similar to EMEP, www.emep.int) with the deposition velocity function of three resistance terms: CASE STUDY (Ozone episode, 2-7 Jul. 1999) Forecast time +37h. Temperature field at 850 hPa (left). Vd is the deposition velocity; Ra the aerodynamic resistance, computed using the friction velocity U* and the stability functions at the surface layer ; Rb the quasi-laminar boundary layer resistance depending upon U* and the molecular diffusivities of the single gases; Rc is the surface resistance generally function of vegetation and soil type. At this stage of development this term is taken constant assuming a different values for each gas. Ozone and wind fields at the lowest model level, about 20m above the terrain (right) COMPARISON WITH GROUND-BASED MEASURES AKNOWLEDGEMENTS Selected references • Buzzi, A., D’Isidoro, M. & S. Davolio: “A case study of an orographic cyclone formation south of the Alps during the MAP-SOP”. Quart. J. Roy. Meteor. Soc, 2003, 129, 1795-1818. • Carter, W. P. L.: “A detailed mechanism for the gas-phase atmospheric reactions of organic compounds”.Atmos. Env., 1990, 24, 481-518.