Hi All
This paper raises some interesting questions.
They are using drop sizes from 10 nanometres to 10 microns. We hope get
as close to a mono-disperse spray of 0.8 microns as is possible. If
drag and inertia of drops are close, the relative velocities due to
local turbulence will be low and collisions less frequent. What would
be the coagulation rates with a much narrower spread of drop diameters?
We also propose to give drops a negative electrostatic charge. How will
this affect coagulation?
If the coagulation rate varies with conditions, do they change slowly
for the spray vessels to be moved to better places?
Stephen
On 20/09/2014 00:02, Andrew Lockley wrote:
Poster's note : The original paper (which should have been posted
first) is here:
http://www.atmos-chem-phys.net/13/10385/2013/acp-13-10385-2013.html
Reduced efficacy of marine cloud brightening geoengineering due to
in-plume aerosol coagulation: parameterization and global implications
G. S. Stuart1, R. G. Stevens1, A.-I. Partanen3, A. K. L. Jenkins2, H.
Korhonen3, P. M. Forster2, D. V. Spracklen2, and J. R. Pierce1,4
Abstract
The intentional enhancement of cloud albedo via controlled sea-spray
injection from ships (marine cloud brightening) has been proposed as a
possible method to control anthropogenic global warming; however,
there remains significant uncertainty in the efficacy of this method
due to, amongst other factors, uncertainties in aerosol and cloud
microphysics. A major assumption used in recent cloud- and
climate-modeling studies is that all sea spray was emitted uniformly
into some oceanic grid boxes, and thus these studies did not account
for subgrid aerosol coagulation within the sea-spray plumes. We
explore the evolution of these sea-salt plumes using a multi-shelled
Gaussian plume model with size-resolved aerosol coagulation. We
determine how the final number of particles depends on meteorological
conditions, including wind speed and boundary-layer stability, as well
as the emission rate and size distribution of aerosol emitted. Under
previously proposed injection rates and typical marine conditions, we
find that the number of aerosol particles is reduced by over 50%, but
this reduction varies from under 10% to over 90% depending on the
conditions. We provide a computationally efficient parameterization
for cloud-resolving and global-scale models to account for
subgrid-scale coagulation, and we implement this parameterization in a
global-scale aerosol-climate model. While designed to address
subgrid-scale coagulation of sea-salt particles, the parameterization
is generally applicable for coagulation of subgrid-scale aerosol from
point sources. We find that accounting for this subgrid-scale
coagulation reduces cloud droplet number concentrations by 46% over
emission regions, and reduces the global mean radiative flux
perturbation from −1.5 W m−2 to −0.8 W m−2.
Citation: Stuart, G. S., Stevens, R. G., Partanen, A.-I., Jenkins, A.
K. L., Korhonen, H., Forster, P. M., Spracklen, D. V., and Pierce, J.
R.: Reduced efficacy of marine cloud brightening geoengineering due to
in-plume aerosol coagulation: parameterization and global
implications, Atmos. Chem. Phys., 13, 10385-10396,
doi:10.5194/acp-13-10385-2013, 2013.
On 15 September 2014 22:21, Andrew Lockley <[email protected]> wrote:
Attached
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