Regulated large-scale annual shutdown of Regulated large-scale annual shutdown of Amazonian isoprene emissions?Amazonian isoprene emissions?

New insight provided by satellite observations of formaldehyde (HCHO) and of New insight provided by satellite observations of formaldehyde (HCHO) and of vegetationvegetation

Michael Barkley & Paul Palmer, University of Edinburgh, UKIsabelle De Smedt & Michel van Roozendael, BIRA-IASB, BelguimThomas Karl & Alex Guenther, NCAR, USA

Michael Barkley, University of Edinburgh

Slide 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 Edinburgh

Slide 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

Slide 4

Where When Importance

Michael Barkley, University of Edinburgh

Slide 5

Where When Importance

Michael Barkley, University of Edinburgh

Slide 6

Where When Importance

Michael Barkley, University of Edinburgh

Slide 7

HCHO over the Amazon

Michael Barkley, University of Edinburgh

Slide 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

Slide 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

Slide 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

Slide 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

Slide 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)

The end!The end!

Michael Barkley, University of Edinburgh

Slide 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

Slide 15

Top-down isoprene emissions

*** GOME HCHO from Harvard ***

Barkley et al., JGR, 2008