Michael Barkley & Paul Palmer, University of Edinburgh, UK

1. Regulated large-scale annual shutdown of Amazonian isoprene emissions?New insight provided by satellite observations of formaldehyde (HCHO) and of vegetation Michael Barkley & Paul Palmer, University of Edinburgh, UK Isabelle De Smedt & Michel van Roozendael, BIRA-IASB, Belguim Thomas Karl & Alex Guenther, NCAR, USA

2. Mapping isoprene emissions from space using HCHO August 1999 • HCHO is significant product of isoprene oxidation • Isoprene emissions are typically main driver of variability in HCHO columns observed from space Michael Barkley, University of Edinburgh

3. Methodology • HCHO column data: • New 12 year data set from BIRA-IASB (De Smedt et al., ACP, 2008) • GOME: 1996-2002 • SCIAMACHY: 2003-2007 • Analysis: • EOF (Empirical Orthogonal Function) Analysis • Take a set of time evolving data and separate the variability into standing oscillation patterns (EOFs) and principal components that show how each mode varies with time • What does EOF analysis tell us? • Most important variability in HCHO columns & therefore of isoprene emissions too • Correlative data: • GEOS-4 model temperature, PAR (diffuse & direct), precipitation • ATSR / AATSR firecounts • MODIS Leaf Area Index (LAI)  size of leaves • MODIS Enhanced Vegetation Index (EVI)  colour of leaves • Multivariate ENSO Index (MEI) (Wolter and Timlin, 1998) Michael Barkley, University of Edinburgh

4. Where When Importance Michael Barkley, University of Edinburgh

5. Where When Importance Michael Barkley, University of Edinburgh

6. Where When Importance Michael Barkley, University of Edinburgh

7. HCHO over the Amazon Michael Barkley, University of Edinburgh

8. Seasonal Variability • Scenes contaminated by fire are excluded using firecounts & NO2 columns • Background HCHO, from the oxidation of non-isoprene species, is taken from a GEOS-Chem simulation for the year 2000 • Satellite data consistent with surface observations of isoprene • ~30% higher in dry season Michael Barkley, University of Edinburgh

9. HCHO response to vegetation activity • LAI - Myneni et al., PNAS, 2007. • Leaf flushing (new leaf growth) during onset of the dry season • EVI – Huete et al., GRL, 2006. • Rainforests green-up with sunlight in dry season • HCHO – Barkley et al, GRL, submitted. • Majority of isoprene emitting species undergo leaf flushing prior to dry season in anticipation of light-rich conditions Michael Barkley, University of Edinburgh

10. HCHO response to vegetation activity • LAI - Myneni et al., PNAS, 2007. • Leaf flushing (new leaf growth) during onset of the dry season • EVI – Huete et al., GRL, 2006. • Rainforests green-up with sunlight in dry season • HCHO – Barkley et al, GRL, submitted. • Majority of isoprene emitting species undergo leaf flushing prior to dry season in anticipation of light-rich conditions Michael Barkley, University of Edinburgh

11. HCHO response to vegetation activity • LAI - Myneni et al., PNAS, 2007. • Leaf flushing (new leaf growth) during onset of the dry season • EVI – Huete et al., GRL, 2006. • Rainforests green-up with sunlight in dry season • HCHO – Barkley et al, GRL, submitted. • Majority of isoprene emitting species undergo leaf flushing prior to dry season in anticipation of light-rich conditions Michael Barkley, University of Edinburgh

12. Summary • HCHO columns provide key insight to Amazonian isoprene emissions: • Seasonal variations of HCHO consistent with satellite observations of vegetation activity • Data strongly suggest large-scale leaf flushing by majority of isoprene emitters results in annual cessation of isoprene emissions • Or, at the very least a severe reduction ! • Big question – Why ? • Towards the future: • Sustained long-term measurement program essential ! • Integration of flux and concentration measurements with satellite observations • HCHO from OMI & GOME-2 – higher spatial resolution • Nested GEOS-Chem with improved VOC chemical mechanism • CRI scheme (Jenkin et al, AE, 2008) Michael Barkley, University of Edinburgh

13. The end!

14. Higher EOF modes • Higher modes: • Show decreased contributions to the total variance • Contain retrieval artefacts (GOME diffuser plate) • Difficult to assign physical meaning  discarded Michael Barkley, University of Edinburgh

15. Top-down isoprene emissions *** GOME HCHO from Harvard *** Barkley et al., JGR, 2008 Michael Barkley, University of Edinburgh