Environmental Engineering Reference
In-Depth Information
SO 4 , black carbon (BC), and particulate organic matter (POM). POM includes
natural secondary organic aerosols. Results have recently been published (Seland
et al., 2008; Kirkevåg et al., 2008; Storelvmo et al., 2008; Seland and Iversen,
2007). Here we diagnose cloud droplet number concentrations (cdnc) from aerosol
activation, but prognostic cdnc is underway. CAM-Oslo is coupled to a slab-ocean
with ocean fluxes calibrated to maintain preseny-day surface temperatures.
This system is used to estimate equilibrium climate response.
Table 1. Experiments identified by aerosol emissions (PI = pre-industrial, PD = present-day) and
CO 2 concentrations (unit ppm: 355 = 1 × CO 2 ; 580 = 1.63 × CO 2 ; 710 = 2 × CO 2 ). Selected key
long-term global results are: T = surface air temperature, P = precipitation, Cl = fractional
cloudiness, LWP = liquid water path, τ = atmospheric life-time, “Aq SO 2 -ox” is the in-cloud
percentage of SO 2 oxidized to sulphate. AOD is the aerosol optical depth at 350-640 nm
Aq.
SO 2 -ox
%
τ
SO 4
d
τ
BC
d
τ
POM
d
τ
SS
d
τ
DU
d
T
K
P
mmd −1
Cl
10 −2
LWP
g m −2
AOD
10 −3
Experiment
1a) PI, 355 290.6 3.10 60.90 106.4 87.30
3.35
6.86
6.98
0.247
2.07
91.4
1b) PD, 355 288.5 2.92 60.27 113.9 85.16 3.78 6.80
7.35
0.256
2.20
130.7
1c) PD, 580 290.5 3.04 60.92 115.6
85.15
3.73
6.66
7.20
0.250
2.21 128.4
2a) PI, 355 288.5 2.93 60.02 127.3 86.92
3.58
6.86
6.96
0.257
2.20
96.2
2b) PD, 355 287.0 2.80 59.52 129.5 84.77 3.97 6.89
7.37
0.265
2.29
138.1
2c) PI, 710 291.2 3.07 60.75 131.3 87.12
3.50
6.86
6.93
0.248
2.21
94.3
2d) PD, 580 289.1 2.92 60.18 132.9 84.83 3.88 6.77
7.23
0.255
2.28
133.3
2e) PD, 710 289.9 2.96 60.41 134.2
84.64
3.89
6.76
7.21
0.253
2.31 132.6
2. Experiments and Results
The aerosols force the climate system by influencing solar radiation and clouds.
Our experiments, as defined in Table 1, are intended for estimating the response
on atmospheric dynamics, SST, and sea-ice. Experiments are 30 years long and
approximate radiative equilibrium is assumed at the top of the atmosphere for
years 15-30. Result statistics from this period are discussed. Experiments 1 are
pre-calibrated with the standard prescribed aerosols in NCAR CAM3, whilst
experiments 2 are pre-calibrated with our own present-day aerosols. Therefore, all
experiments 1 have a slight positive bias since the PD conditions differ slightly
from the conditions used when calibrating the ocean fluxes. There is a tendency
that aerosol life-times are short when precipitation is high and v.v., but since
precipitation may increase in areas with small aerosol loading this is not always
the case. In experiments 2, a background cloud droplet number concentration (cdnc)
of 3 cm 3 over oceans and the Antarctic and 17 cm 3 over continents is added.
 
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