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

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

Michael Barkley, University of EdinburghSlide 3 Methodology  HCHO column data: ♦ New 12 year data set from BIRA-IASB (De Smedt et al., ACP, 2008) ♦ GOME: ♦ SCIAMACHY:  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 EdinburghSlide 4 WhereWhenImportance

Michael Barkley, University of EdinburghSlide 5 WhereWhenImportance

Michael Barkley, University of EdinburghSlide 6 WhereWhenImportance

Michael Barkley, University of EdinburghSlide 7 HCHO over the Amazon

Michael Barkley, University of EdinburghSlide 8 Seasonal Variability  Scenes contaminated by fire are excluded using firecounts & NO 2 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 EdinburghSlide 9 HCHO response to vegetation activity  LAI - Myneni et al., PNAS, ♦ Leaf flushing (new leaf growth) during onset of the dry season  EVI – Huete et al., GRL, ♦ 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 EdinburghSlide 10 HCHO response to vegetation activity  LAI - Myneni et al., PNAS, ♦ Leaf flushing (new leaf growth) during onset of the dry season  EVI – Huete et al., GRL, ♦ 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 EdinburghSlide 11 HCHO response to vegetation activity  LAI - Myneni et al., PNAS, ♦ Leaf flushing (new leaf growth) during onset of the dry season  EVI – Huete et al., GRL, ♦ 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 EdinburghSlide 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)

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