English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Due to the scarcity ofobservational constraints and the rapidly changing environment in East andSoutheast Asia, isoprene emissions predicted by models are expected to bearsubstantial uncertainties. The aim of this study is to improve upon theexisting bottom-up estimates, and to investigate the temporal evolution ofthe fluxes in Asia over 1979–2012. To this purpose, we calculate the hourlyemissions at 0.5°×0.5° resolution using theMEGAN–MOHYCAN model driven by ECMWF ERA-Interim climatology. In order toremedy for known biases identified in previous studies, and to improve thesimulation of interannual variability and trends in emissions, this studyincorporates (i) changes in land use, including the rapid expansion of oilpalms, (ii) meteorological variability according to ERA-Interim, (iii)long-term changes in solar radiation (dimming/brightening) constrained bysurface network radiation measurements, and (iv) recent experimental evidencethat South Asian tropical forests are much weaker isoprene emitters thanpreviously assumed, and on the other hand, that oil palms have a strongisoprene emission capacity. These effects lead to a significant lowering(factor of 2) in the total isoprene fluxes over the studied domain, and toemission reductions reaching a factor of 3.5 in Southeast Asia. The bottom-upannual isoprene emissions for 2005 are estimated at 7.0, 4.8, 8.3, and2.9 Tg in China, India, Indonesia and Malaysia, respectively. The isopreneflux anomaly over the whole domain and studied period is found to be stronglycorrelated with the Oceanic Niño Index (<i>r</i> = 0.73), with positive(negative) anomalies related to El Niño (La Niña) years.  Changes in temperature and solar radiation are the major drivers of theinterannual variability and trends in the emissions, except over semi-aridareas such as northwestern China, Pakistan and Kazakhstan, where soilmoisture is by far the main cause of interannual emission changes. In ourbase simulation, annual positive flux trends of 0.2% and 0.52%throughout the entire period are found in Asia and China, respectively,related to a positive trend in temperature and solar radiation. The impact ofoil palm expansion in Indonesia and Malaysia is to enhance the trends overthat region, e.g., from 1.17% to 1.5% in 1979–2005 in Malaysia. Anegative emission trend is derived in India (−0.4%), owing to thenegative trend in solar radiation data associated with the strong dimmingeffect likely due to increasing aerosol loadings.  The bottom-up emissions are compared to field campaign measurements in Borneoand South China and further evaluated against top-down isoprene emissionestimates constrained by GOME-2/MetOp-A formaldehyde columns through2007–2012. The satellite-based estimates appear to support our assumptions,and confirm the lower emission rate in tropical forests of Indonesia andMalaysia. Additional flux measurements are clearly needed to characterize thespatial variability of emission factors better. Finally, adecreasing trend in the inferred top-down Chinese emissions since 2007 is inline with recorded cooling in China after that year, thus suggesting that thesatellite HCHO columns are able to capture climate-induced changes inemissions

Isoprene emissions over Asia 1979–2012: impact of climate and land-use changes