Isoprene emissions in Asia 1979-2012 : Isoprene emissions in Asia 1979-2012 : variability and trends, effects of changes variability and trends, effects of changes in meteorology and land use, in meteorology and land use, and comparison to top-down estimatesand comparison to top-down estimates

Jenny Stavrakou, Jean-François Müller, Maite BauwensIsabelle De Smedt, Michel Van RoozendaelBelgian Institute for Space Aeronomy, Brussels

Alex GuentherAtmospheric Chemistry Division, NCAR, Table Mesa Drive, Boulder, US

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, negative climate forcing

Key actor in chemistry-biosphere-climate interactions

Why focus on Asia? Two of world’s most rapidly expanding economies and almost ½ of world population

Dramatic changes in emissions : o In China NOx emissions doubled in only 10 years, PM2.5

increase by 2.7 between 1990 and 2005

Massive land use changes with huge environmental impacts, forests crops urban, urbanized Beijing area doubled in 1985-1992!

Massive deforestation oil palm plantations in Southeast Asia, Indonesia&Malaysia: 85-90% of the global oil palm production, oil palm: large isoprene emitter

Heavy aerosol loading likely impacts SR reaching the ground (dimming)

How do these effects influence the emitted isoprene?

Model outline

LAIdzdSdtFlux SMageTP

canopy

Emission rate in standard conditions

Response functions to radiation and T at leaf level

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)

Focus : 9 S-55 N, 60-150 E, 0.5°x0.5°, Focus : 9 S-55 N, 60-150 E, 0.5°x0.5°, Step = 0.5 h, Step = 0.5 h, S0 = S0 = Base runBase runFocus : 9 S-55 N, 60-150 E, 0.5°x0.5°, Focus : 9 S-55 N, 60-150 E, 0.5°x0.5°, Step = 0.5 h, Step = 0.5 h, S0 = S0 = Base runBase 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

Main drivers are : warming rates & radiation trends

Annual % isoprene trend

Decadal T trend (oC) 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 % PAR trend

Isoprene trend is stronger in NE China, Northern Borneo (3%/year)

Isoprene Flux Anomaly

Asia : negative deviations related to WLN (1984-85), SLN (1988-1989), SLN (1999), MLN (2007-2008), positive to MEN (1987), SEN (97-98), MEN (2009-2010), China : little correlation with El Niňo

Relation with Oceanic Niňo Index (ONI)

r = 0.73r = 0.73, in agreement with past studies

ONI is lagged to account for potentially complex influence of ENSO on isoprene emissions

Land use changes1979-2007 trend in cropland

fraction1979-2007 cropland fraction

evolution

Ramankutty and Foley (1999)

Rapid crop expansion in Southeast Asia, related to large-scale deforestation, Indonesia (1.5%/yr), Malaysia (2.3%/yr)

Crop abandonment in Central & South China

%/yr

Oil palm plantations

Fraction of oil palm plantations in 2010

Koh et al. (2011)Miettinen et al. (2012)http://bepi.mpob.gov.my

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

Solar radiation changes

Annual surface solar radiation anomaly data

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)

Measurement sites

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

SimulationSimulation DescriptionDescription

S0S0 standardstandard

S1S1as S0, account for as S0, account for

land use changesland use changes

S2S2 as S1, reduction of isoprene rate for tropical as S1, reduction of isoprene rate for tropical

forestsforests

by factor of 4.1 (Langford et al. 2010) by factor of 4.1 (Langford et al. 2010)

S3S3as S2, emissions from oil palms as S2, emissions from oil palms

in Indonesia&Malaysiain Indonesia&Malaysia

S4S4as S3, effect of solar radiation as S3, effect of solar radiation

changes and correction changes and correction

factors from Jia et al. (2013)factors from Jia et al. (2013)

Best bottom-upBest bottom-up

Isoprene emissions across S0-S4 in 2005 (mg isoprene/m2/s)

S0 (90 Tg)S0 (90 Tg) S1 (71 S1 (71 Tg)Tg)

S2 (42 S2 (42 Tg)Tg)

S4 (40 S4 (40 Tg)Tg)

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 decreased because we have adopted decreased SR fields

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

Evaluation against top-down estimates

HCHO is major intermediate product in the oxidation of isoprene in the atmosphere

Past studies demonstrated the capabilities of HCHO columns to infer isoprene emissions

GOME-2 HCHO July 2010

A priori IMAGESv2 HCHO

Optimized columns

1015 molec.cm-2

Use 2007-2012 GOME-2 HCHO, De Smedt et al., AMT, 2012, http://www.temis.nlPerform grid-based inversion with IMAGESv2 global CTM for 6 years using S4 bottom-up as a priori, x2.5 error on biogenic flux

1010 molec. cm-2 s-1

2008 a priori isoprene emission Emission change (optimized-prior)

Small changes wrt the prior, by up to 30% higher emission in SE China, by up to 30% lower emission in Borneo

Satellite data support the strong reduction of emission rate for tropical forests in Indonesia and Malaysia

Tg/yr

Conclusions Best bottom-up inventory has lower emissions by factor of

2 compared to MEGANv2 this enhances the relative importance of anthropogenic emissions to the total VOC budget !

Lower emissions o due to drastic emission rate reduction in tropical

forests Need for additional measumentso due to more extensive cropland and lower solar

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