Update on: 1. Secondary Organic Aerosol 2. Biogenic VOC emissions Colette L. Heald Chemistry Climate Working Group Meeting February 12, 2008

MODELING FRAMEWORK Community Land Model (CLM3) Datasets: Lawrence and Chase [2007] Feddema et al. [2007] LAI (MODIS) Plant Functional Types Soil moisture Vegetation Temperature BVOC Algorithms [Guenther et al., 1995; 2006] Monterpenes: GEIA Isoprene: MEGAN Community Atmospheric Model (CAM3) Chemistry Transport Radiation BVOC Emissions Vegetation Meteorology Radiation Precipitation SOA production Anthropogenic Emissions, GHG concentrations, SST

SECONDARY ORGANIC AEROSOL FORMATION Reactive Organic Gases OH, O 3, NO 3 Monoterpenes Aromatics Isoprene OH SOA Condensation of low vapour pressure ROGs on pre- existing aerosol SOA parameterization [Chung and Seinfeld, 2002] VOC i + OXIDANT j   i,j P1 i,j +  i,j P2 i,j Parameters (  ’s K’s) from latest smog chamber studies (Caltech) A i,j G i,j P i,j Equilibrium (Kom i,j )  also f(POA) Y~2-5%Y~15%Y~25%

SOA: WHAT IS IN “MY VERSION” OF CAM-CHEM 2-product model SOA 3 classes of SOA (5 tracers): –Monoterpenes (+OH, +O 3, +NO 3 ) [Chung and Seinfeld, 2002] –Isoprene (+OH) [Henze and Seinfeld, 2006] –Aromatics (Benzene, Toluene, Xylene + OH) [Henze et al., 2008] Yields are dynamically NOx dependent Include temperature sensitive partitioning coefficients Iteratively solves for gas-particle equilibrium at every time-step (therefore carry gas phase SOA = SOG as tracers), allows for re- volatilization BOTTOM LINE: addition of SOA/SOG, and rudimentary oxidation scheme for aromatics adds many tracers: –5 SOA, 5 SOG, Xylene/Benzene + oxidation products = 18 CAM-Chem now includes the state of the art for parameterized SOA modeling. PROBLEM: This may not be enough! DISCUSSION: Are simplifications possible to incorporate into Ghan aerosol scheme? Is this desirable?

STATUS: BVOC EMISSIONS IN CLM3.5 MONOTERPENES: As in Levis et al. [2003] Based on Guenther et al. [1995] ANNUAL TOT: 43 TgC/yr ISOPRENE: MEGAN v2 [Guenther et al., 2006] (includes T, PAR, soil moisture, LAI, leaf age) ANNUAL TOT: 495 TgC/yr Note: To run with MEGAN2 need new fsurdat file for CLM with isoprene basal emission rates Fluxes passed from CLM  CAM TO DO: Implement MEGAN2 emission factors for 19 other species (monoterpenes, sesquiterpenes, other OVOCs, etc.). Associated changes to chemical mechanism?

Several plant growth studies show that isoprene emission is inhibited in a high-CO 2 environment. INHIBITION OF ISOPRENE EMISSION DUE TO CO 2 [Possell et al., 2005] Mick Wilkinson and Russ Monson (UC Boulder) have examined isoprene emission for 4 plant species as a function of both short-term and long- term CO 2 exposure. They have parameterized the observed relationships for one species (aspen) which can be added to the MEGAN v2 activity factors [Wilkinson et al., in prep]. Some preliminary results when implemented in CLM…

FOR PRESENT-DAY (2000): EFFECT IS SMALL Annual global total isoprene emissions increase by 7% (from 495 TgC/yr to 530 TgC/yr (mostly in Australia, Amazon)

FOR FUTURE (2100 A1B): CO 2 INHIBITION COMPENSATES FOR TEMPERATURE INCREASE Future projected emissions drop from 615 TgC/yr to 506 TgC/yr (again, primarily in Australia and the Amazon) See that ↑in T activity factor ~ compensated by ↓ in CO 2 activity factor Dotted=2000 Solid=2100

CONCLUSION: ISOPRENE EMISSIONS PREDICTED TO REMAIN ~CONSTANT Important implications for oxidative environment of the troposphere… [Heald et al., in prep]

MEGAN v2 COMPOUNDS Compound/Class Name Class IDEF BT EF NT EF SHR EF GC  Leaf Age CaseLDF Isoprene1map 51 MBO Myrcene Sabinene limonene carene ocimene pinene pinene farnescene caryophyllene Methanol Acetone Acetaldehyde and ethanol formic acid, formaldehyde, acetic acid methane nitrogen gases: NO, NH3, N2O other monoterpenes other sesquiterpenes other VOC