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Jenny Stavrakou, Jean-François Müller, Maite Bauwens Isabelle De Smedt, Michel Van Roozendael

Isoprene emissions in Asia 1979-2012 : variability and trends, effects of changes in meteorology and land use, and comparison to top-down estimates. Jenny Stavrakou, Jean-François Müller, Maite Bauwens Isabelle De Smedt, Michel Van Roozendael

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Jenny Stavrakou, Jean-François Müller, Maite Bauwens Isabelle De Smedt, Michel Van Roozendael

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  1. Isoprene emissions in Asia 1979-2012 : variability and trends, effects of changes in meteorology and land use, and comparison to top-down estimates Jenny Stavrakou, Jean-François Müller, Maite Bauwens Isabelle De Smedt, Michel Van Roozendael Belgian Institute for Space Aeronomy, Brussels Alex Guenther Atmospheric Chemistry Division, NCAR, Table Mesa Drive, Boulder, US

  2. Isoprene is important because… • Most abundant VOC emitted by vegetation, global annual emissions of ~500 TgC • Highly reactive : with OH (< 1h), O3 (1-2 h) and NO3 (~1 d) but its degradation in the atmosphere is still not completely elucidated  • Leads to ozone formation in polluted conditions : ISOP+OH RO2+HO2 (+NO)  NO2  O3 • Source of SOA  Health impact, negativeclimate forcing • Key actor in chemistry-biosphere-climate interactions

  3. Why focus on Asia? • Two of world’smostrapidlyexpanding • economies and almost ½ of world population • Dramatic changes in emissions : • In China NOxemissionsdoubled in only 10 years, PM2.5increase by 2.7 between 1990 and 2005 • Massive land use changes withhugeenvironmental impacts, forests crops  urban, urbanized Beijing area doubled in 1985-1992! • Massive deforestation  oil palm plantations in SoutheastAsia, Indonesia&Malaysia: 85-90% of the global oil palm production, oil palm: large isopreneemitter • Heavy aerosolloadinglikely impacts SR reaching the ground (dimming) How do these effects influence the emitted isoprene?

  4. Model outline Response functions to radiation and T at leaf level Emission rate in standard conditions Dependence to leaf age and soil moisture stress Leaf area index • Latest database of MEGAN basal emission rates • LAI : collection 5 8-day MODIS • ERA-Interim ECMWF analyses for downward solar radiation, temperature, wind, humidity, cloudiness & soil moisture in 4 layers • Vertical profiles inside the canopy obtained from a 8-layer canopy model (MOHYCAN, Müller et al., 2008)

  5. Focus : 9 S-55 N, 60-150 E, 0.5°x0.5°, Step = 0.5 h, S0 = Base run Strong interannual variability, highest isoprene flux in 1997-98, due to exceptional El Nino, lowest emission in 1984&2008 Largest emission flux in 2007, lower emissions afterwards

  6. Main drivers are : warming rates & radiation trends

  7. Decadal T trend (oC) Annual % PAR trend • Strongest warming trend : close to Shanghai (0.4-0.6oC/decade)& Northern provinces, in agreement with Liu et al.(2004) analysis • Warming rates < 0.4oC/decade in Southern China • Positive trend in radiation in Southern China, negative in Indonesia Annual % isoprene trend Isoprene trend is stronger in NE China, Northern Borneo (3%/year)

  8. Isoprene Flux Anomaly • Asia : negativedeviationsrelated to WLN (1984-85), SLN (1988-1989), SLN (1999), MLN (2007-2008), positive to MEN (1987), SEN (97-98), MEN (2009-2010), China : littlecorrelationwith El Niňo

  9. Relation with Oceanic Niňo Index (ONI) • r = 0.73, in agreement withpaststudies • ONI islagged to account for potentiallycomplex influence of ENSO on isopreneemissions

  10. Land use changes 1979-2007 trend in cropland fraction 1979-2007 cropland fraction evolution %/yr Ramankutty and Foley (1999) • Rapidcrop expansion in SoutheastAsia, related to large-scaledeforestation, Indonesia (1.5%/yr), Malaysia (2.3%/yr) • Cropabandonment in Central & South China

  11. Fraction of oil palm plantations in 2010 Oil palm plantations • 250-m resolution land cover map (Miettinen et al., 2012) gridded onto 0.5 deg. • Planted palm area expanded extremely rapidly in1979-2010, factor of 55 in Sarawak, 20 in Indonesia and Sabah, 3 in Peninsular Malaysia Koh et al. (2011) Miettinen et al. (2012) http://bepi.mpob.gov.my

  12. Measurement sites Solar radiation changes • ECMWF SR data fail to reproduce the observations, changes in aerosol loading are omitted • ECMWF overestimates by 8-20% ground observations of SR in China (Jia et al. 2013) Annual surface solar radiation anomaly data • Solar dimming in China until 1990, most pronounced in eastern China, brightening after 1990 in SE China • Significant brightening in Japan over 1990-2002 • Over India strong solar dimming after 1985

  13. Isoprene emissions across S0-S4 in 2005 (mg isoprene/m2/s) S1 (71 Tg) S0 (90 Tg) S2 (42 Tg) S4 (40 Tg)

  14. Trend reinforced in S1 due to negative trend in cropland fraction in China • Consider SR changes in S4  further trend enhancement due to brightening in SE China, emissions have decreasedbecausewe have adopteddecreased SR fields

  15. Strong emission trend in S0, due to 0.2o-0.6oC/decade warming rates & positive radiation trend, warming rate exceeds by far the global 20th century warming rate (0.6oC, IPCC) • Increasing trend in cropland fraction in S1  reduces trend • x2-3 emission reduction in S2 • Further trend enhancement in S3, due to the expansion of oil palm plantations

  16. Evaluation against top-down estimates • HCHO is major intermediateproduct in the oxidation of isoprene in the atmosphere • Paststudiesdemonstrated the capabilities of HCHO columns to inferisopreneemissions • Use 2007-2012 GOME-2 HCHO, De Smedt et al., AMT, 2012, http://www.temis.nl • Perform grid-based inversion with IMAGESv2 global CTM for 6 years using S4 bottom-up as a priori, x2.5 error on biogenic flux 1015 molec.cm-2 GOME-2 HCHO July 2010 A priori IMAGESv2 HCHO Optimizedcolumns

  17. 2008 a priori isoprene emission Emission change (optimized-prior) 1010 molec. cm-2 s-1 • Small changes wrt the prior, by up to 30% higheremission in SE China, by up to 30% loweremission in Borneo • Satellite data support the strongreduction of emission rate for tropical forests in Indonesia and Malaysia Tg/yr

  18. Conclusions • Best bottom-up inventory has loweremissions by factor of 2 compared to MEGANv2  thisenhances the relative importance of anthropogenicemissions to the total VOC budget ! • Loweremissions • due to drasticemission rate reduction in tropical forests Need for additionalmeasuments • due to more extensive cropland and lowersolar radiation over China compared to ECMWF • High isoprene emission rate from oil palms in combination with rapid oil palm expansion causes higher trend over Indonesia and Malaysia • Top-down estimates confirm lower emission rate for tropical forests & corroborate the decreasing trend over China due to the cooling epidode since 2007

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