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SUMMARY:Reconciling top-down versus bottom-up isoprene emissions from the 
 Amazon Basin - Dr Michael P. Barkley\, University of Leicester
DTSTART:20101115T141500Z
DTEND:20101115T151500Z
UID:TALK25915@talks.cam.ac.uk
CONTACT:Dr Alex Archibald
DESCRIPTION:Satellite observations of formaldehyde (HCHO) columns provide 
 additional top-down constraints on isoprene emissions and are especially u
 seful in assessing isoprene emissions from remote and largely inaccessible
  tropical ecosystems. I will present results from two studies: (a) an anal
 ysis of top-down Amazonian isoprene emissions\, inferred from GOME HCHO co
 lumns observations using the GEOS-Chem chemistry transport model and the M
 EGAN (Model of Emissions of Gases and Aerosols from Nature) bottom-up inve
 ntory\, and (b) an empirical orthogonal function analysis on 12 years of g
 lobal GOME and SCIAMACHY HCHO column observations.\n\nI will show that in 
 most regions\, HCHO variability is predominantly driven by seasonal variat
 ions of biogenic emissions and biomass burning. However\, unusually low HC
 HO columns are consistently observed over western Amazonia\, during the tr
 ansition from the wet-to-dry seasons.  Seasonal variations in MODIS Leaf A
 rea Index (LAI) and Enhanced Vegetation Index (EVI) data are remarkably co
 nsistent (correlations of 0.69 and 0.67\, respectively) with the observed 
 decrease in HCHO during the wet-to-dry period. Based on this evidence\, it
  is possible isoprene emitters experience widespread leaf flushing prior t
 o the dry season\, resulting in a large-scale annual shutdown of Amazonian
  isoprene emissions.\n\nIn addition to these studies\, I will show prelimi
 nary model and data comparisons to assess the accuracy of a newly develope
 d GEOS-Chem (high-resolution) nested grid Amazon simulation.\n
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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