the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Intra- and inter-annual changes in isoprene emission from central Amazonia
Eliane Gomes Alves
Raoni Aquino Santana
Cléo Quaresma Dias-Júnior
Santiago Botía
Tyeen Taylor
Ana Maria Yáñez-Serrano
Jürgen Kesselmeier
Pedro Ivo Lembo Silveira de Assis
Giordane Martins
Rodrigo Souza
Sérgio Duvoisin Júnior
Alex Guenther
Anywhere Tsokankunku
Matthias Sörgel
Bruce Nelson
Davieliton Pinto
Shujiro Komiya
Diogo Martins Rosa
Bettina Weber
Cybelli Barbosa
Michelle Robin
Kenneth J. Feeley
Alvaro Duque
Viviana Londoño Lemos
Maria Paula Contreras
Alvaro Idarraga
Norberto López A.
Chad Husby
Brett Jestrow
Abstract. Isoprene is a chemical compound emitted naturally by soil, microorganisms, plants, and animals into the atmosphere. But plants are the largest emission source, and the amount of emission depends on plant species, weather conditions, and environmental conditions, including exposure to environmental stresses such as heat and drought. Isoprene is very reactive in the atmosphere and is involved in atmospheric physicochemical processes that can impact atmospheric chemistry, air quality, and regional climate. Quantification and understanding of the atmospheric processes influenced by isoprene result from a combination of observational experiments and estimates obtained from computational models. However, only a few long-term observational experiments have been conducted in the largest source of isoprene to the global atmosphere – the Amazon rainforest, and there are still uncertainties in the model estimates. Recent experiments have also shown that the models have greater uncertainty when estimating intra- and inter-annual variations in isoprene. This study aimed to improve our understanding of isoprene emission from a central Amazonian site by considering biological and environmental factors influencing emission on intra- and interannual time scales. By combining observational datasets, we adapted a widely used computational model of isoprene emission to observed conditions in the field. Our observations indicated that isoprene emission was not as high as the model estimated when the forest experienced environmental stress, such as heat and drought, in the 2015 El-niño year. In addition, observations revealed that the model performed well when diurnal variations were analyzed but not when long-term variations occurred. The performance for estimating intra- and inter-annual isoprene emission improved when the model was modified on two biological factors – (i) the amount of different leaf ages throughout the year and (ii) the emission rates of these different leaf ages. This shows that isoprene emission estimates can be improved when biological processes are mechanistically incorporated into the model.
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Eliane Gomes Alves et al.
Status: open (until 05 Apr 2023)
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RC1: 'Comment on egusphere-2023-168', Anonymous Referee #2, 07 Mar 2023
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Well-written paper showing isoprene concentration and flux (11 days) measurements with PTR-TOF-MS and its comparison to various MEGAN model runs at ATTO site, central Amazonia. Paper shows for the first time emission factors of isoprene which differs by tree species and age. That makes this contribution special. In addition, authors did multiple MEGAN model runs to show comparison of measured fluxes of isoprene by eddy covariance and MEGAN with and without those specific Es. Results show substantial improvement; however, an overestimation of MEGAN model still remains. Authors discuss that the reason, among other, might be an emission of "heavier" compounds instead of isoprene.
Paper reads well and goes directly to the point. Maybe in discussion there should be mention the uncertainty of isoprene emissions by eddy covariance itself. If isoprene would be measured with H3O+ primary ions (which reader unfortunately does not know), then 232MBO (2-methyl-3-buten-2-ol) goes to m/z 69.07 too. However, maybe authors did their measurement in NO+ mode. Or isoprene might be fragmented and therefore you measured lower fluxes. Anyway, it should be clarified in M&M part and discussed properly.
Here are more detailed remarks:
line 145: 2380 mm of precipitation is average from 2013-2019?
line 162: please indicate the exact version of PTRMS by Ionicon, primary ions used, E/N ratio, Td. Please indicate calibration here too. Was isoprene present in the cylinder? Although it is in Yãnez-Serrano et al. (2015), it should be mentioned here too. In addition, version of the instrument and primary ions used is not mentioned even in Yãnez-Serrano et al. (2015).
line 175: indicate frequency of anemometer
line 244: "was determined by laboratory analysis" - sounds odd
line 372: "Combretaceae" should be in italics too
fig 2: fig would benefit from making x and y axes descriptions bigger
line 448: what does mean "higher gross primary productivity (GPP) fluxes"? I think it should be without "fluxes"
Citation: https://doi.org/10.5194/egusphere-2023-168-RC1
Eliane Gomes Alves et al.
Eliane Gomes Alves et al.
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