Role of aerosol chemical composition on the formation of cloud condensation nuclei during biomass burning periods Swen Metzger 1, Ivonne Trebs 1, Laurens Ganzeveld 1, Jos Lelieveld 1, Philip Stier 2, Franz X. Meixner 1, Meinrat O. Andreae 1, Paulo Artaxo 3 Swen Metzger 1, Ivonne Trebs 1, Laurens Ganzeveld 1, Jos Lelieveld 1, Philip Stier 2, Franz X. Meixner 1, Meinrat O. Andreae 1, Paulo Artaxo 3 Wednesday, 28/07/04, III LBA Scientific Conference - Brasília, July 27-29, Max-Planck Institute for Chemistry, Mainz, Germany 2 Max-Planck Institute for Meteorology, Hamburg, Germany 3 Instituto de Fisica, Universidade de Sao Paulo, Brasil © Greg Roberts

Introduction  The chemical composition of atmospheric aerosols plays an important role for the hygroscopic growth and the aerosol- associated water mass.  Biomass burning events are likely to alter the chemical composition due to the emission of inorganic cations, such as potassium, and organic acids.  We therefore investigate their impact on the chemical composition and on the aerosol water mass, which is important for the cloud formation.

Thermodynamical aerosol model: EQSAM; Gas/liquid/solid partitioning HNO 3, NH 3, H 2 SO 4, HCl, organic acids (g) Ions, liquid phase NO 3 -, NH 4 +, SO 4 2-, Cl -, lumped Low Molecular Weight (LMW) organic acids (e.g., HCOOH), Na +, K +, Ca 2+, Mg 2+, H 2 O, pH Salts, Solid phase NH 4 NO 3, NH 4 HSO 4, (NH 4 ) 2 SO 4, NH 4 & organic acids Temperature & relative humidity R1R1 NH 4 NO 3, NH 4 HSO 4, (NH 4 ) 2 SO 4, NH 4 & organic acids NO 3 -, NH 4 +, SO 4 2-, Cl -, LMW organic acids (e.g., HCOOH), Na +, K +, Ca 2+, Mg 2+, H 2 O, pH R2R2

Model Application - SMOCC Data Na/Cl-NH 3 /NH 4 -HNO 3 /NO 3 -H 2 SO 4 /SO 4 -H 2 O-System Reduced aerosol systems compare relatively good for the wrong reason ! Model simulations: box model constrained with observed T, RH & total gas- particulate mass (Trebs et al., in prep.)

K-Ca-Mg-Na/Cl-NH 3 /NH 4 -HNO 3 /NO 3 -H 2 SO 4 /SO 4 -H 2 O-System with K-Ca-Mg as equivalent Na All models compare reasonable well when applied with the same complexity Model Application - SMOCC Data But they all underestimate the observed aerosol NH 4 + concentration!

Model Application - SMOCC Data K-Ca-Mg-Na/Cl-NH 3 /NH 4 -HNO 3 /NO 3 -H 2 SO 4 /SO 4 -H 2 O-System with K-Ca-Mg considered explicitly in EQSAM/SCAPE2 Crustal elements considered in EQSAM; same ammonium loss as SCAPE2 K + drives NH4 + out of the aerosol phase, in contrast to the observations! Reduced aerosol systems for Isorropia compares relatively good for the wrong reason !

Model Application - SMOCC Data LMW organic acids gets the ammonium back in the aerosol phase Including LMW organic acids in EQSAM Reduced aerosol systems for Isorropia compares relatively good for the wrong reason ! Consistent inclusion of K + and LMW organic acids in EQSAM

Modular Earth Submodel System (MESSy) coupled to GCM ECHAM5 ECHAM5 Polar Stratospheric Clouds micro-physics and sedimentation Polar Stratospheric Clouds micro-physics and sedimentation Aerosol Physics (& chemistry) Thermodynamical aerosol composition module and size-resolving dynamical module Aerosol Physics (& chemistry) Thermodynamical aerosol composition module and size-resolving dynamical module 14 CO / Radon natural atmospheric tracer, evaluation of tropospheric OH. STE / PBL transport 14 CO / Radon natural atmospheric tracer, evaluation of tropospheric OH. STE / PBL transport Eulerian Transport Schemes Lagrangian Transport Scheme Natural and Anthropogenic Emissions biogenic surface emissions and anthropogenic emissions Natural and Anthropogenic Emissions biogenic surface emissions and anthropogenic emissions Gas-phase and Heterogeneous Chemistry using Kinetic PreProcessor (KPP) Gas-phase and Heterogeneous Chemistry using Kinetic PreProcessor (KPP) MBL Chemistry switchable extension with chemistry scheme MBL Chemistry switchable extension with chemistry scheme Photolysis fast on-line scheme Photolysis fast on-line scheme Diagnostic and Output (e.g., PBL and tropopause height) Diagnostic and Output (e.g., PBL and tropopause height) Scavenging Below and in-cloud scavenging of gases and aerosols Scavenging Below and in-cloud scavenging of gases and aerosols Dry Deposition dry deposition of gases and aerosols Dry Deposition dry deposition of gases and aerosols Convection & Tracer Transport Stratospheric Water Vapor Lightning NOx Coupled chemistry-GCM

G: 6 N: 7 M: 34 total: N 2. BC-OA1a 3. BC-OA2a 4. NO 3 5.NH 4 6. SO 4 7. SOA1 8. SOA2 1. N 2. SO4 3. BC => BC-OA1a, BC-OA2a 4. OC => SOA1 8. SOA2 5. SS => SS-Na 12.SS-Cl 6. DU => DU1, DU2 7./8./9. NO 3, NH 4, H 2 O 1. N 2. BC-OA1a 3. BC-OA2a 4. NO 3 5. NH4 6. SO 4 7. SOA1 8. SOA2 9. DU1 10.DU2 11. SS-Na 12.SS-Cl 1. N 2. H2SO 4 Nucleation Aitken Accumulation Coarse H 2 SO 4 NH 3 HNO 3 SOA1 SOA2 HCl soluble (liquid/solid) 1. N 2. BC-OA1 (primary) 3. BC-OA2 (primary) 1. N 2. DU3 (solid Si-core) 1. N 2. DU3 (solid Si-core) insoluble (solid) Gasphase New M7/EQSAM Structure Coupled chemistry-GCM: Aerosol modeling As an example:

EQSAM-M7: Aerosol Water [1e-9 kg/kg] (ug/kg) (PBL monthly mean, august) Coupled chemistry-GCM: Aerosol modeling

M7: Aerosol Water [1e-9 kg/kg] Coupled chemistry-GCM: Aerosol modeling

ECHAM5: Cloud Water [1e-6 kg/kg] Coupled chemistry-GCM: Aerosol modeling EQSAM-M7: Aerosol Water [1e-9 kg/kg]M7: Aerosol Water [1e-9 kg/kg] Qualitive comparison of cloud and aerosol water spatial distribution

 There is a larger spatial variability in the global distribution of the EQSAM-M7 aerosol water compared to M7, which only includes non-volatile sodium and sulfate Conclusion/Outlook  Comparison of the aerosol NH 4 + content simulated with EQSAM and LBA- SMOCC observations shows the aerosol chemical composition needs to be included consistently, e.g., for biomass burning including not only potassium but also LMW acids. For detailed questions/remarks:  The spatial variability in the EQSAM-M7 aerosol water is more similar compared to the spatial variability in ECHAM5’s cloud water, suggesting that the more detailed representation of the aerosol chemical composition in EQSAM-M7 will facilitate a direct coupling of the aerosol model to ECHAM5’s cloud representation with respect to CCN activation.

 Evaluation of the ECHAM5 water/cloud fields, coupled to EQSAM-M7, with satellite observations (R. Lang).  Calculations of CCN and ICN in MESSy-ECHAM5 by explicitly coupling the cloud- and aerosol water content based on the ionic composition that reflects the actual aerosol composition (incl. gas/liquid/solid aerosol partitioning) Outlook For detailed questions/remarks:

1.Metzger, S. M., Gas/Aerosol Partitioning: A simplified Method for Global Modeling, Ph.D. Thesis, University Utrecht, The Netherlands, Metzger, S. M., F. J. Dentener, J. Lelieveld, and S. N. Pandis, Gas/aerosol Partitioning I: A Computationally Efficient Model. J Geophys. Res., 107, D16, /2001JD001102, Metzger, S. M., F. J. Dentener, A. Jeuken, and M. Krol, J. Lelieveld, Gas/aerosol Partitioning II: Global Modeling Results. J Geophys. Res., 107, D16, /2001JD001103, Metzger, S. M., Gas/aerosol partitioning III: Model development (EQSAM) and comparison (MINOS Data), in preparation. The new version of EQSAM has been successfully applied within the EMEP modelling framework. Results are included in the EMEP reports, Trebs, I., S. Metzger, F. X. Meixner, G. Helas, A. Hoffer, M. O. Andreae, M. A.L. Moura, R. S. da Silva (Jr.), J. Slanina, Y. Rudich, A. Falkovich, P. Artaxo, The NH 4+ -NO 3– -Cl – -SO 42– -H 2 O system and its gas phase precursors at a rural site in the Amazon Basin: How relevant are crustal species and soluble organic compounds?, in preparation for JGR. References