New insight on the impacts of Earth's biosphere on air quality

Date:
September 9, 2020
Source:
University of Minnesota
Summary:
A new study provides the first global satellite measurements of
one of the most important chemicals affecting Earth's atmosphere.



FULL STORY ==========================================================================
A new study led by a team of University of Minnesota researchers provides
the first global satellite measurements of one of the most important
chemicals affecting Earth's atmosphere.


========================================================================== Isoprene is a natural hydrocarbon emitted to the atmosphere in vast
quantities -- approximately 500 billion kg per year -- by plants and
trees. Isoprene is chemically reactive, and once in the atmosphere
it combines with human-caused pollutants to adversely affect air
quality. Isoprene also reacts with the main atmospheric oxidizing agent -- called OH radicals -- and therefore reduces the capacity of the atmosphere
to scrub itself of pollutants and greenhouse gases.

Scientists look to atmospheric models to predict current and future
atmospheric composition and air quality, as well as to diagnose the atmosphere's ability to remove greenhouse gases and air pollutants. But isoprene emission rates are highly uncertain due to sparse ground-based measurements, and scientists are also unsure of the extent to which
isoprene acts to suppress or sustain the abundance of OH radicals in
the atmosphere.

Now, researchers have developed the first-ever global measurements of
isoprene from space. Using observations from the Cross-track Infrared
Sounder (CrIS) satellite sensor, researchers developed a retrieval method
that uses machine learning to determine the atmospheric concentration
of isoprene over different parts of the world. They combined these
measurements with atmospheric modeling to test current scientific
understanding of global isoprene emissions and how isoprene affects
atmospheric oxidation. The research will be published on Wednesday,
September 9 in the journal Nature.

"Isoprene is one of the most important drivers of global atmospheric chemistry," said Dylan Millet, a professor in the U of M's Department
of Soil, Water, and Climate. "These satellite measurements provide
new understanding of how Earth's biosphere and atmosphere interact."
By combining the CrIS isoprene measurements with other satellite data,
for the first time researchers were able to estimate the abundance of
OH from space over isoprene source regions. These observations support
recent laboratory and theory-based findings: isoprene emissions do
lower atmospheric OH, but not nearly as strongly as was originally
believed. As a result, the atmosphere maintains a significant ability
to scrub itself of pollution even in the presence of natural isoprene emissions. Combining these measurements with other space-based data will
open new doors to investigate changes in OH over time.

This research lays a foundation for multi-year studies examining
seasonal-to- interannual isoprene changes and their impacts on the
global atmosphere.

Information from these new satellite measurements can also be used to
improve current atmospheric models, with the goal of more accurately
predicting air quality in a changing climate.

Researchers revealed that:
* -The satellite measurements of isoprene show dramatic model
overestimates
over Amazonia. These disparities indicate a strong need for better
understanding of tropical emissions of isoprene and other reactive
chemicals.

-Over southern Africa, the CrIS measurements reveal a major isoprene
hotspot that is missing from bottom-up predictions. This points
to a need for further investigation of isoprene sources in this
understudied region.

"These new satellite measurements reveal that, while our understanding of isoprene chemistry is getting pretty good, we still have a lot to learn
about how isoprene emissions vary across Earth's different ecosystems,"
said Kelley Wells, a researcher in the Department of Soil, Water,
and Climate in the U of M's College of Food, Agricultural and Natural
Resource Sciences.


========================================================================== Story Source: Materials provided by University_of_Minnesota. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Wells, K.C., Millet, D.B., Payne, V.H. et al. Satellite isoprene
retrievals constrain emissions and atmospheric oxidation. Nature,
2020 DOI: 10.1038/s41586-020-2664-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200909114835.htm

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