Solar radiation management by use of
air lubrication method
Suginori Iwasaki and Nanami Doi
National Defense Academy, Japan.
Introduction 1
All geoengineering methods do not make any profit.
Figure from Lenton and Vaughan (2009, ACP)
2
Introduction 2:
Air Lubrication Method (ALM)
bow
Fuel efficiency = +8-12%
(Mizokami et al., 2011)
Ship wake
air supply
opening
bubble
stern
flow
Diagram of the ALM
(Mizokami et al. 2011).
Bubbles of
ALM + Ship wake
The reflectance and area of ALM bubbles
are greater than those of ship wake.
The ship wake photo
of ALM experiment
(from Dr. Hinatsu,
3
NMRI).
Introduction: 3
Previous study
Gatebe et al. (2011) showed the radiation forcing of normal ship
wakes was -1.4×10-4 W/m2, ~10-4 times smaller than that of CO2.
This study
 Simulate the bi-directional reflection distribution
function of ALM by the ray-tracing method.
 Estimate radiative forcing of ALM bubbles.
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Method 1: Ray-tracing method
BRDF λ  in , in , out ,  out  
Count
(θ in,φin)
(θ out,φout)
I λ  out ,  out 
Fλ  in , in 
Count
(θ out,φout)
Decide scattering /
absorption by random
numbers
Stop below draft
Scattering: Mie scattering
Absorption: Lambert-beer law
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Method 2: Bubble distribution
τ ~ 20s (Garrett, 1967)
r = 50% (Whitlock, 1982)
draft: 5m
homogeneous & log-normal distribution
Bubbles size distribution of
the experiment of ALM,
Nagamatsu et al. (2002)
Mode radius: 308µm
Standard dev.: 1.67
Number density: 1.28×105/m3
Total vol. of bubbles: 2mm/m2
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Results: Bi-directional Reflective Distribution Function (BRDF)
ALM test vessel
308 µm and 2mm/m2 bubbles
Time [min]
Averaged BRDF
ALM imaginary vessel
30 µm and 5mm/m2 bubbles
Time [hours]
Obs. of normal wake
Gatebe et al. (2011)
Simulation 1
Test vessel
308μm, 2mm/m2
Simulation 2
Imaginary vessel
30μm, 5mm/m2
0.032
0.14
0.37
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Radiative forcing
Radiative forcing =
(W/m2)
×
×
×
solar flux on sea surface (W/m2)
number of ships
If all have ALM
wake area / Earth area
wake albedo (Liang et al., 2005)
Gatebe et al. (2011, GRL)
We simply estimate the radiative forcing by ALM bubbles,
BRDF of 1 vessel
Normal albedo
=
BRDF of 1 ALM vessel
ALM albedo
Gatebe et al. (2011)
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Results: Normal wakes vs. ALM wakes
Av. albedo
Normal wake
Gatebe et al.(2011)
ALM wake
Test vessel
308µm, 2mm/m3
ALM wake
Imaginary vessel
30µm, 5mm/m3
0.018
0.079
0.21
coast
294m
Wake area (km2)
2.17
Radiative forcing
(W/m2)
−1.4×10-4
×100
0.02
ocean
105m
−5.7×10-6
4.5
ocean
105m
−3.4×10-3
×25
1.
2.
Wake area, lifetime of foam, is needed to
research!
Smaller ALM bubbles would have a
potential for geoengineering.
# GHG emission of all ships is 2.7% of the
global total (Second IMO GHG Study 2009).
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