Supplement of Geosci. Model Dev., 7, 1535–1542, 2014
http://www.geosci-model-dev.net/7/1535/2014/
doi:10.5194/gmd-7-1535-2014-supplement
© Author(s) 2014. CC Attribution 3.0 License.
Supplement of
An investigation into the performance of four cloud droplet activation
parameterisations
E. Simpson et al.
Correspondence to: G. McFiggans ([email protected])
Supplementary Material
Demonstration of Time Dependency in Model Simulations
Supplementary Figure 1 demonstrates the large amount of simulation time required by
the parcel model in order to activate a fraction of large aerosol, 1000 nm.
1.1
RH
1.05
1
0.95
Fraction of Activated Drops
0.9
0
1
2
3
4
5
Time (s)
6
4
5
Times (s)
6
7
8
9
4
x 10
1
0.8
0.6
0.4
0.2
0
0
1
2
3
7
8
9
4
x 10
Fig. 1: Time series of peak RH (top panel) and fraction of activated drops (bottom
panel) as calculated by ACPIM with initial conditions described in Table 1, aerosol
number concentration 500 cm−3 , and mean aerosol diameter 1000 nm.
1
Single-Mode Experiment
Supplementary Figure 2 shows that the performance of the four parameterisations is
generally good in single lognormal aerosol size distribution of small aerosol (5 ≤ dm ≤
250 nm) at high number concentration, 10000 cm−3 . However there is a tendency to
underestimate the fraction of activated drops.
1
Fraction of Activated Drops Parameterisation
0.9
0.8
200
0.7
0.6
150
0.5
0.4
100
0.3
ARG
0.2
0.1
0
0
50
FN
FN GCCN
FN GCCN BM
0.2
0.4
0.6
0.8
Fraction of Activated Drops Parcel Model
1
Fig. 2: Results from 1500 runs with 1 lognormal mode of ammonium sulphate aerosol,
number concentration of 10000 cm−3 . Symobols are coloured by mean aerosol diameter (nm). The values for the following variables were randomly chosen within the
stated ranges: 0.2 ≤ ln σ ≤ 0.8; median diameter, 5 ≤ dm ≤ 250 nm; updraft velocity,
0.01 ≤ w ≤ 10 m s−1 . Initial conditions are detailed in Table 1.
Supplementary Figure 3 shows that the four parameterisations highly overestimate
2
the fraction of activated drops in single lognormal aerosol size distribution of large
aerosol (250 ≤ dm ≤ 2000 nm) at low number concentration, 100 cm−3 .
1
Fraction of Activated Drops Parameterisation
0.9
1800
0.8
1600
0.7
1400
0.6
1200
0.5
1000
0.4
800
0.3
ARG
0.2
600
FN
FN GCCN
0.1
0
0
FN GCCN BM
0.2
0.4
0.6
0.8
Fraction of Activated Drops Parcel Model
400
1
Fig. 3: Results from 1500 runs with 1 lognormal mode of ammonium sulphate aerosol,
number concentration of 100 cm−3 . Symbols are coloured by median aerosol diameter.
The values for the following variables were randomly chosen within the stated ranges:
0.2 ≤ ln σ ≤ 0.8; median diameter, 250 ≤ dm ≤ 2000 nm; updraft velocity, 0.01 ≤ w ≤ 10
m s−1 . Initial conditions are detailed in Table 1.
Supplementary Figures 4 and 5 show the same results as Figure 2 with data points
coloured coded by ln σ and aerosol number concentration respectively. There is no
obvious relationship between the fraction of activated drops estimated by the parameterisations and variables mentioned.
3
1
0.75
0.9
Fraction of Activated Drops Parameterisation
0.7
0.8
0.65
0.7
0.6
0.6
0.55
0.5
0.5
0.45
0.4
0.4
0.3
0.2
0.35
FN
0.3
FN GCCN
0.1
0
0
ARG
0.25
FN GCCN BM
0.2
0.4
0.6
0.8
Fraction of Activated Drops Parcel Model
1
Fig. 4: Results from 1500 runs with 1 lognormal mode of ammonium sulphate aerosol
and randomly sampled variables values as detailed in Table 2 and initial conditions
described in Table 1. Symbols are coloured by ln σ, see colour bar.
4
Fraction of Activated Drops Parameterisation
1
0.9
1800
0.8
1600
0.7
1400
0.6
1200
0.5
1000
0.4
800
0.3
600
ARG
0.2
FN
0
0
400
FN GCCN
0.1
200
FN GCCN BM
0.2
0.4
0.6
0.8
Fraction of Activated Drops Parcel Model
1
Fig. 5: Results from 1500 runs with 1 lognormal mode of ammonium sulphate aerosol
and randomly sampled variables values as detailed in Table 2 and initial conditions
described in Table 1. Symbols are coloured by aerosol number concentration (number
cm−3 ), see colour bar.
Dual-Mode Experiment
To avoid extreme conditions of very high concentrations of large or small aerosol the
parameter space has been limited in the following cases. The range of updraft velocity
has also been limited so that within the simulation time of the parcel model the “effective
height” of the rising air parcel is more realistic, i.e between 0.4 km and 10km, where
clouds form.
5
Using a smaller parameter space improves the results from the four parameterisations as can be seen in Supplementary Figure 6.
1
0.9
Fraction of Activated Drops Parameterisation
700
0.8
600
0.7
0.6
500
0.5
400
0.4
300
ARG
0.3
FN
200
FN GCCN
0.2
FN GCCN BM
0.1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Fraction of Activated Drops Parcel Model
0.9
1
Fig. 6: Results from 1500 runs with bimodal aerosol size distributions, 500 cm−3 in the
first mode and 100 cm−3 in the second. Only the median diameter of aerosol in the
second mode and updraft velocity were changed between runs, within the ranges of
100 ≤ dm ≤ 800 nm and 0.2 ≤ w ≤ 5 m s−1 respectively. Symbols are coloured by
median diameter (nm) of the second mode, see colourbar. For initial conditions see
Table 1.
6