j.-f. müller, j. stavrakou, s. wallens belgian institute for space aeronomy, brussels, belgium
DESCRIPTION
Interannual variability of biogenic VOC emissions estimated from the MEGAN model and ECMWF analyses. J.-F. Müller, J. Stavrakou, S. Wallens Belgian Institute for Space Aeronomy, Brussels, Belgium. A. Guenther National Center for Atmospheric Research, Boulder, Colo., USA. - PowerPoint PPT PresentationTRANSCRIPT
J.-F. Müller, J. Stavrakou, S. Wallens
Belgian Institute for Space Aeronomy, Brussels, Belgium
IUGG Symposium, July 2007
Interannual variability of biogenic VOC emissions estimated from the MEGAN
model and ECMWF analyses
A. GuentherNational Center for Atmospheric Research, Boulder, Colo., USA
Thanks to: J. Rinne (Univ. Helsinki), M. Potosnak (Desert Res. Institute), B. Munger and S. Wofsy (Harvard Univ.), A. Goldstein (Univ. California),
M. Van Roozendael and I. De Smedt (IASB, Brussels)
Outline MEGAN model : emission algorithm MOHYCAN model: canopy environment
model Results: Inventory for 1995-2006 Interannual variability Comparison with campaign data Evaluation using GOME HCHO data
MEGAN model for estimating the emissions of isoprene from plant foliage
= emission rate in standard conditions
, = response functions to radiation and temperature at leaf level
= dependence to leaf age
= dependence to soil moisture stress
LAI = Leaf Area Index
• LAI from MODIS 2000-2006
• ECMWF analyses provide: canopy top values of downward solar radiation, temperature, wind, and humidity + cloudiness + soil moisture in 4 layers
• values inside the canopy require a multi-layer canopy model (MOHYCAN)
(Wallens, 2004; Müller et al., 2007)
LAIdzdSdtFlux SMageTP
canopy
P TageSM
ε
Results : Emissions in 2003
Very similar to distribution obtained by Guenther et al. (ACP2006) using NCEP meteorological data, except over arid areas
Results: Impact of soil moisture stress
Large reduction over arid areas
Global annual emissions reduced by > 20%
Results: Impact of using leaf (instead of air) temperature in the algorithm
Global annual emission increased by 18%
Results: Zonally averaged emissions
Global annual emission is ~30% than in Guenther et al. (1995, 2006)
Large interannual variability (20% difference between extreme years)
Isoprene emissions and El Niño
Comparison with campaign data: Harvard forest, Mass., 1995
Diurnal cycle is OKDay-to-day variations very well reproduced
Overestimation in spring/fall
Comparison with campaign data: Tapajos, Amazonia, 2000, 2001, 2003
(Here model results scaled down by factor 1.7)
Wet season fluxes (April-July) largely overestimated by model
GOME HCHO data
Slant columns retrieved at IASB-BIRA (I. De Smedt, M. Van Roozendael) from GOME spectra using the WinDOAS technique
Fitting window chosen to avoid artefacts over desert areas and reduce noise
Vertical HCHO profiles taken from IMAGES CTM
http://www.temis.nl, De Smedt et al., in preparation
Vertical HCHO columns calculated by the IMAGES CTM (curves) and retrieved from GOME (diamonds)
Using GEIA inventory
Using MEGAN-based inventory
Id., neglecting soil moisture stress
Conclusions
Isoprene emission inventory 1995-2006 at 0.5°x0.5° resolution available at http://www.oma.be/TROPO/inventory.html in NetCDF format
Müller et al., will be soon submitted to ACP
Soil moisture stress might have a big impact, but the calculated effect depends on choice of meteorological data + wilting point database
Global emission is ~410 Tg/year
Large interannual variability, to a great extent related to El Niño
Short-term variations of isoprene emissions well captured by model, not so much the seasonal variation
Satellite HCHO : a promising tool for constraining the emission distribution and variability also in Tropical regions