Towards a holistic understanding of the interactions between biochemical and physical processes above the Amazonian rain forest

8 Feb
Atmospheric & Environmental Chemistry Seminar
Jordi Vila, Wageningen University
Friday, February 8, 2019 - 12:00pm to 1:00pm
Pierce 100F

The dry season in the Amazonian rain forest is characterized by shallow cumulus,
which perturbs both radiation and turbulence above the tropical forest. These
disturbances lead to continuous changes in the partitioning of the available energy in
evapotranspiration and sensible heat flux at the surface. The non-steady state of the
radiative and turbulent conditions also influence the emission and subsequent transport
of biogenic volatile organic compounds. In turn, the spatiotemporal variations in the
surface fluxes of the energy, water and atmospheric compounds modify the atmospheric
boundary layer dynamics, and therefore thus the diurnal cycle of shallow cumulus. More
specifically, turbulent thermals may change in intensity and vertical extent, and changes
in aerosol composition will lead to differences in the distribution of the aerosol properties
that may influence the cloud condensation nuclei. Both effects impact the cloud
microphysics and dynamics.
In this seminar, I present and discuss recent results that reproduce a
representative day in the Amazonian rain forest during the dry season. Guided and
constrained by the complete observational set gathered during the GOAMAZON
campaign, we have designed a suite of numerical experiments performed by the Dutch
Atmospheric Large Eddy Simulation (DALES). Our main aim is to study the interaction of
the biochemical and physical processes that occur on sub-hourly and sub-kilometre
scales. The numerical experiments explicitly simulate the coupling between the surface
and the atmospheric boundary layer. Here, we focus on processes that affect
photosynthesis, such as cloud shading, the impact of the partitioning of direct and diffuse
radiation in and above the canopy, and the effects of the wind on the energy and
moisture fluxes. I will close the seminar by discussing experiments that include gas-
phase chemistry to study the diurnal variability of reactive compounds on the Amazonian
tropical forest.

Scot Martin
Kelvin Bates