Cropland trees need to be included for accurate model simulations of land-atmosphere heat fluxes, temperature, boundary layer height, and ozone

A. K. Mishra, B. Sinha, R. Kumar, M. Barth, H. Hakkim, V. Kumar, A. Kumar, S. Datta, A. Guenther, V. Sinha*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Trees significantly impact land-atmosphere feedbacks through evapotranspiration, photosynthesis and isoprene emissions. These processes influence the local microclimate, air quality and can mitigate temperature extremes and sequester carbon dioxide. Despite such importance, currently only 5 out of 15 atmospheric chemistry climate models even partially account for the presence of cropland trees. We first show that the tree cover over intensely farmed regions in Asia, Australia and South America is significantly underestimated (e.g. only 1–3% tree cover over north-India) in the Model of Emissions of Gases and Aerosol from Nature (MEGAN) and absent in Noah land-surface module of the Weather Research and Forecasting (WRF-Chem) Model. By including the actual tree cover (~10%) over the north-west Indo Gangetic Plain in the Noah land-surface module of the WRF-Chem and the MEGAN module, during the rice growing monsoon season in August, we find that the latent heat flux alone increases by 100%–300% while sensible heat flux reduces by 50%–100%, leading to a reduction in daytime boundary layer height by 200–400 m. This greatly improves agreement between the modelled and measured temperature, boundary layer height and surface ozone, which were earlier overestimated and isoprene and its oxidation products which were earlier underestimated. Mitigating peak daytime temperatures and ozone improves rice production by 10 to 20%. Our findings from north west Indo-Gangetic Plain establish that such plantations mitigate heat stress, and have beneficial effects on crop yields while also sequestering carbon. Expanding agroforestry practices to 50% of the cropland area could result in up to 40% yield gain regionally. Implementing such strategies globally could increase crop production and sequester 0.3–30 GtC per year, and therefore future climate mitigation and food security efforts should consider stakeholder participation for increased cropland agroforestry in view of its beneficial effects.

Original languageEnglish
Article number141728
JournalScience of the Total Environment
Volume751
Early online date19 Aug 2020
DOIs
Publication statusPublished - 10 Jan 2021

Bibliographical note

Funding Information:
This work has been supported through grant (SPLICE) DST/CCP/MRDP/100/2017(G) under the National Mission on Strategic knowledge for Climate Change (NMSKCC) MRDP Program of the Department of Science and Technology , India. High-performance computing support from Cheyenne (doi: https://doi.org/10.5065/D6RX99HX ) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation is gratefully acknowledged. The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. A.K.M, H.H. and A.K acknowledge IISER Mohali for funding PhD fellowships, VK acknowledges DST-INSPIRE and S.D. acknowledges UGC for funding PhD fellowships.

Funding Information:
We thank past and present members of the IISER Mohali Atmospheric Chemistry and Emissions and Aerosol Research Groups for technical assistance. We acknowledge use of the WRF-Chem preprocessor tools (mozbc, fire_emiss, anthro_emis) provided by the Atmospheric Chemistry Observations and Modelling Lab (ACOM) of NCAR. Prof. A.R. Ravishankara is gratefully acknowledged for helpful discussions. This work has been supported through grant (SPLICE) DST/CCP/MRDP/100/2017(G) under the National Mission on Strategic knowledge for Climate Change (NMSKCC) MRDP Program of the Department of Science and Technology, India. High-performance computing support from Cheyenne (doi:https://doi.org/10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation is gratefully acknowledged. The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. A.K.M, H.H. and A.K acknowledge IISER Mohali for funding PhD fellowships, VK acknowledges DST-INSPIRE and S.D. acknowledges UGC for funding PhD fellowships. All primary data including the one related to resampled MOD44B and corresponding matched Globe cover LULC dataset is available upon request from vsinha@iisermohali.ac.in.

Publisher Copyright:
© 2020 Elsevier B.V.

Keywords

  • Agroforestry
  • Air quality
  • Crop yield
  • Heat stress
  • Land-atmosphere interactions

Cite this