1. Terrestrial emissions of isoprene Paul Palmer Division of Engineering and Applied Sciences, Harvard University http://www.people.fas.harvard.edu/~ppalmer

2. NO HO 2 OH NO 2 O3O3 hv HC+OH  HCHO + products NOx, HC, CO Tropospheric O 3 is an important climate forcing agent IPCC, 2001 Level of Scientific Understanding Natural VOC emissions (50% isoprene) ~ CH 4 emissions.

3. GEIAEPA BEIS2 7.1 Tg C 2.6 Tg C MEGAN 3.6 Tg C [10 12 atom C cm -2 s -1 ] Isoprene emissions July 1996 Isoprene oxidation products (e.g. HCHO) provide constraints on estimated emissions

4. GOME isoprene emissions (July 1996) agree with surface measurements ppb 0 12 r 2 = 0.53 Bias -3% GEIA BEIS2 r 2 = 0.65 Bias -30% Modeled HCHO [ppb] Observed HCHO [ppb]

5. Modeling the terrestrial biosphere April Sep LAI PAR – direct and diffuse (GMAO) MODIS/AVHRR LAI Canopy model (Guenther 1995) Altitude Emission Temperature: Instantaneous (G95) 10-day avg (Petron ‘01) Fixed base emission factors (Guenther 2004) Emissions

6. Monthly mean LAI (AVHRR/MODIS) MEGAN (isoprene) Canopy model Leaf age LAI Temperature Base factors MODEL BIOSPHERE GEIA Monoterpenes MBO Acetone Methanol GEOS-CHEM Global 3D CTM PAR, T Emissions Global 3-D Modeling Overview Driven by NASA GMAO met data 2x2.5 o resolution/30 vertical levels O 3 -NO x -VOC-aerosol chemistry

7. May Jun Jul Aug Sep [10 12 atom C cm -2 s -1 ] VOC emissions during 2001 growing season Isoprene Monoterpenes MBO

8. GEOS-CHEM NO x = 1 ppb NO x = 0.1 ppb isoprene Use this analysis to parameterise source of HCHO from monoterpenes HCHO production from biogenics using the MCM HOURS 0.5 Cumulative HCHO yield [per C]  pinene (  pinene similar) DAYS 0.4 0.33 Y become closer at t progresses further Mike Pilling and Jenny Stanton, Leeds University

9. Nadir-viewing SBUV instrument Pixel 320 x 40 km 2 10.30 am cross-equator time (globe in 3 days) O 3, NO 2, BrO, OClO, SO 2, HCHO, H 2 O, cloud Global Ozone Monitoring Experiment HCHO slant columns fitted: 337-356nm Fitting uncertainty < continental signals HCHO JULY 1997 Isoprene Biomass Burning

10. May Jun Jul GEOS-CHEM GOME Aug Sep GEOS-CHEM GOME HCHO column [10 16 molec cm -2 ] GROWING SEASON 2001 HCHO column signal from monoterpenes is comparable to GOME column uncertainty

11. HCHO data over the Ozarks c/o Y-N. Lee, Brookhaven National Lab. Missouri Illinois Kansas [ppb] Aircraft data @ 350 m July 1999 OZARKS SOS 1999 [10 16 molec cm -2 ] GOME

12. Relating HCHO Columns to VOC Emissions k HCHO  HCHO E VOC = _______________ k VOC Yield VOC  HCHO VOC source Distance downwind  HCHO Isoprene  -pinene propane 100 km VOC HCHO hours OH hours h, OH Ultimate Yield Y (per C) Approx. Time to Y isoprene~0.52-3 hrs  pinene ~0.33-4 days  pinene ~0.253-4 days MBO~0.43-4 days Master Chemical Mechanism

13. Wind direction associated with largest [HCHO] in 1998 intensive EVALUATE GOME DATA USING LONG-TERM ISOPRENE FLUX DATA PROPHET RESEARCH SITE (MI) Maple, beech, birch, basswood, mixed aspen, bog conifers (lower, wet areas), and pine and red oak (drier upland regions). Average height near 20 m. Overstory age of the hardwood forest is approximately 75 years.

14. Long term in situ isoprene flux measurements at PROPHET site during 2001 Y2K1 Day HCHO column [10 16 molec cm -2 ] Isoprene flux [10 12 molec cm -2 s -1 ] Measured (WSU) MEGAN GOME +/- uncertainty Isoprene flux [10 12 molec cm -2 s -1 ] Measured (WSU) MEGAN GOME Using observed isop flux:HCHO column regression  better agreement with GOME

15. May June July August September 1996 1997 1998 1999 2000 2001 HCHO column [10 16 molec cm -2 ]

16. Interannual variability of the seasonal cycle GOME HCHO Column [10 16 molec cm -2 ] Days 2K1 Southeast US 32-38N; 265-280W

17. In situ observations over Atlanta GA provide some verification of large interannual variability GOME HCHO Column [10 16 molec cm -2 ] PAMS (EPA) Isoprene Concentration (10-12 LT) [ppbC] r = 0.75 n=14 Mean values associated with individual values > 30 ppbC Lance McCluney, EPA

18. What is driving this variability? Curve based on greenhouse data (Guenther) 2 nd -order polynomial fit to HCHO columns r=0.9

19. Closing Remarks GOME HCHO data provide constraints on natural VOC emissions Data consistent with seasonal and interannual variability observed with in situ measurements Improved understanding and quantification of air quality and climate Just the beginning…need to relate model- observation discrepancy to a better understanding of the underlying processes