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Research
Publications
CV
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Tropical convection and its representation in general
circulation models (GCMs)
My currect project involves leading the way towards a new
convection parameterisation for GCMs. The scheme should be able
to represent the stochasticity of tropical convection because
this is most commonly not represented in current convection
parameterisations. As atmospheric convection is most probably
the most uncertain aspect of atmospheric modelling, finding a
new and perhaps better way to represent its effect in GCMs is of
utmost importance.
This paper details the analysis of observed convective behaviour
over two tropical locations (Darwin and Kwajalein). Further, the
stochastic multicloud model (SMCM) deloped by Boualem Khouider, Andrew Majda and colleagues is found to
adequately reproduce the observed convective behaviour.
Currently, I am working on implementing the framework of the
SMCM into a GCM convective parametrization in collaboration with
the convection group at the UK Met Office.
Influence of aerosol-cloud interactions on climate
Indirect aerosol effects
Indirect aerosol effects, i.e. the influence of aerosols on
cloud microphysical properties, are the largest source of
uncertainty when estimating climate sensitivity. To reduce this
uncertainty, much basic research is needed.
I investigated the influence of shipping emissions on clouds by means
of satellite and model data.
- Simulations with the aerosol climate model ECHAM5-HAM show that the aerosol indirect effect from shipping emissions
may be substantially lower than previously estimated and that the
emission parameterisation has substantial influence on the
results. See my PhD-Thesis
for results.
- From analysis of satellite data, we find no statistical significant influence of shipping
emissions on cloud fields in the regions of interest. The
accompanying paper is found here.
That paper was chosen as a research
highlight by Nature Climate Change
Direct aerosol effects
For most atmospheric aerosol species, scattering dominates over
absorption of radiation in the visible spectral range. The direct
radiative forcing (DRF) at the top of the atmosphere (TOA) exerted
by a layer of aerosol depends on the albedo of the underlying
surface and the aerosol single scattering albedo (SSA). In
cloud-free scenes, even strongly (but still also scattering)
absorbing aerosols impose a negative TOA DRF over ice-free oceanic
regions due to the dark underlying surface -- the local planetary
albedo α is increased. If the surface albedo is increased,
such as in case of clouds residing below aerosols, absorbing
aerosols can exert a positive TOA DRF. In this case, the
absorption of the particles dominates the scattering for the net
TOA effect -- α is decreased.
Our paper investigating this effect from satellite data only can be
found here.
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