Abstract
In response to a warming climate, temperature extremes are changing in many regions of the world. Therefore, understanding how the fluxes of sensible heat, latent heat and net ecosystem exchange respond and contribute to these changes is important. We examined 216 sites from the open access Tier 1 FLUXNET2015 and free fair-use La Thuile data sets, focussing only on observed (non-gap-filled) data periods. We examined the availability of sensible heat, latent heat and net ecosystem exchange observations coincident in time with measured temperature for all temperatures, and separately for the upper and lower tail of the temperature distribution, and expressed this availability as a measurement ratio. We showed that the measurement ratios for both sensible and latent heat fluxes are generally lower (0.79 and 0.73 respectively) than for temperature measurements, and the measurement ratio of net ecosystem exchange measurements are appreciably lower (0.42). However, sites do exist with a high proportion of measured sensible and latent heat fluxes, mostly over the United States, Europe and Australia. Few sites have a high proportion of measured fluxes at the lower tail of the temperature distribution over very cold regions (e.g. Alaska, Russia) or at the upper tail in many warm regions (e.g. Central America and the majority of the Mediterranean region), and many of the world's coldest and hottest regions are not represented in the freely available FLUXNET data at all (e.g. India, the Gulf States, Greenland and Antarctica). However, some sites do provide measured fluxes at extreme temperatures, suggesting an opportunity for the FLUXNET community to share strategies to increase measurement availability at the tails of the temperature distribution. We also highlight a wide discrepancy between the measurement ratios across FLUXNET sites that is not related to the actual temperature or rainfall regimes at the site, which we cannot explain. Our analysis provides guidance to help select eddy covariance sites for researchers interested in understanding and/or modelling responses to temperature extremes.
Original language | English |
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Pages (from-to) | 1829-1844 |
Number of pages | 16 |
Journal | Biogeosciences |
Volume | 16 |
Issue number | 8 |
DOIs | |
Publication status | Published - 30 Apr 2019 |
Bibliographical note
Funding Information:Acknowledgements. Andrew J. Pitman, Martin G. De Kauwe, Anna Ukkola and Gab Abramowitz acknowledge support from the Australian Research Council Centre of Excellence for Climate Extremes (CE170100023). Sophie V. J. van der Horst would like to thank Bert Holtslag of Wageningen University for his comments on the manuscript and his help in arranging the internship. This work used eddy covariance data acquired by the FLUXNET community and in particular by the following networks: Amer-iFlux (US Department of Energy, Biological and Environmental Research, Terrestrial Carbon Program: DE–FG02–04ER63917 and DE–FG02–04ER63911), AfriFlux, AsiaFlux, CarboAfrica, Car-boEuropeIP, CarboItaly, CarboMont, ChinaFlux, Fluxnet Canada (supported by CFCAS, NSERC, BIOCAP, Environment Canada and NRCan), GreenGrass, KoFlux, LBA, NECC, OzFlux, TCOS– Siberia, USCCC. We acknowledge the financial support to the eddy covariance data harmonisation provided by CarboEuropeIP, FAO–GTOS–TCO, iLEAPS, Max Planck Institute for Biogeochemistry, National Science Foundation, University of Tuscia, Univer-sité Laval, Environment Canada and US Department of Energy and the database development and technical support from the Berkeley Water Center, Lawrence Berkeley National Laboratory, Microsoft Research eScience, Oak Ridge National Laboratory, University of California and University of Virginia.
Publisher Copyright:
© Author(s) 2019.