James Ciarlo
Ciarlo`,, Noel Aquilina
University of Malta, Department of Physics
MedCLIVAR Workshop, ICTP, Trieste
23rd – 25th September 2010
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PRECIS & Physical Parameters
Why the Mediterranean Basin?
The Sulfur Cycle & Aerosols
Aerosol Impacts
Sulfur Cycle Validation
Data Analysis
Atmospheric Sulfur Chemistry
Conclusions
2

The
REgional
for
Th PRECIS (Providing
(P
idi
RE i
l Climates
Cli
f Impact
I
Studies)
◦ RCM is driven by
y the GCM HadAM3P. ((Gordon et al, 2000))


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Clouds & precipitation
Radiation includes the seasonal and diurnal cycles of solar
radiation
Land Surface characteristics are p
prescribed according
g to
climatological surface types
S
f
h
Surface
exchanges
• Land surface scheme is MOSES (Met Office Surface Exchange
Scheme). (Cox et al, 1999)
3
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Enclosed by 3 major continents.
Surrounded almost entirely
y by
y mountains.
Very unique and sensitive to climate changes.
Simulation details
◦
◦
◦
◦
◦
◦
GCM-HadAM3P-150km
GC
d
3 1 0k
PRECIS (v 1.7.2) used
1960-1990 (1-year spin up)
Resolution: 0.44° x 0.44°
100 cells x (50 km x 50 km)
57°N-18°N,, 16°W-46°E
4
Mode
Nucleation
Aitken
Diameter
(μm)
<0.01
Lifetime
Removal Process
Minutes-Hours Coagulation
0.01-0.1
Hours-Days
Accumulation
0.1-1
Weeks
Nucleation
Coarse
1-10
Hours-Days
Gravitation
Giant
>10
Hours-Days
Gravitation

Coagulation
The Sulfur Cycle is based 5 variables:
 SO2, DMS and 3 modes of SO422- (1 dissolved & 2 free modes)
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Model simulates transport of above, via horizontal and
vertical advection
advection, convection and turbulent mixing
Aerosols act as CCN
Increase in aerosol causes climate impacts
5
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With increasing aerosol activity:
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Direct: Scattering effect
◦ Decreased: SW
SW, Skin T
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Indirect: Cloud albedo (Twomey) effect
◦ Decreased:
D
d Di
Diurnall T
Temperature R
Range (DTR)
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Indirect: Cloud lifetime effect
◦ Decreased: Precipitation, DTR
6
Aerosol Impacts within the PRECIS output:
 Studied through correlation between aerosolsensitive parameters.
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Direct effect:
◦ Correlations between
0.60-0.82
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Indirect effects:
◦ Correlations between
0 18-0
0.18
0.82
82
◦ Complex interactions
◦ Cannot isolate Cloud
albedo effect from
the Twomey
Effect
Effect
Direct
Indirect
Direct
Indirect
Direct
Indirect
Direct
Indirect
Direct
Correlation
Correlation
Aitken v SW
-0.76
v Skin T
-0.77
AccumDiss
v SW
-0.82
DissTv SW
-0.82
SW v Skin
0.69
v DTR
0.50
Aitken vSWSkin
T
-0
0.60
60
v DTR
-0.59
AccumCLW
v Skin
T
-0.64
Indirect
I di t
Indirect
Indirect
Cloud lifetime
Cloud lifetime
Indirect
Indirect
Indirect
Diss v CLW
CLW v SW
Diss v DTR
Diss v PPN
CLW v PPN
CLW v LW
Diss v LW
LW v DTR
0.39
-0.28
0 28
-0.40
0.43
0.18
-0.26
-0.60
0.47
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Measured
Modelled
Min = 107.4; Max = 234.7
Min = 68.9; Max = 256.4
1961-1990
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9
10
Statistics of Parameters
Parameter
C
Conv
PPN ( 10‐66)
PPN (x10
DTR
Net LW
Net SW
RH Surface T
Surface T
Correlation
0 47
0.47
‐0.11
0.48
0.59
0.43
0 13
0.13
Average Bias
‐3.08
3 08
‐1.98
1.01
‐10.45
‐5.46
0 82
0.82
Max Bias
‐1.48
1 48
‐0.32
3.77
‐6.99
‐3.01
1 59
1.59
Min Bias
‐5.80
5 80
‐3.52
‐1.37
‐15.63
‐8.38
0 05
0.05
◦ Bias of Conv PPN, DTR, Net LW, Net SW, RH:
 Suggest SO422- over-prediction
over prediction
◦ Bias of Surface Temperature:
 Possible result of Net LW over-prediction
over prediction
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12
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13
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PRECIS yearly average concentrations:
◦ HO• - constant.
 HO• causes no variation in DMS and SO2 oxidation

U i
Using
Pearson
P
Correlation:
C
l ti
◦ SO2 is correlated to dissolved SO422
◦ DMS is negatively
negati el correlated to dissol
dissolved
ed SO42◦ H2O2 is negatively correlated to Aitken &
accumulation SO42◦ Aitken is correlated to accumulation SO42◦ Accumulation is correlated to dissolved SO42[All correlations are statistically significant (p<0.01),
except the first, which is p<0.05]
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◦ Sulfur Cycle Validation:
 Direct: High evidence
 Indirect: Varying evidence
◦ Results suggest problems with the Sulfur cycle:
 Possible over-estimation of SO42- concentrations
◦ Correlation of SO42- and H2O2 shows the SO2 to H2O2 reaction is
the most important within PRECIS
◦ Correlations show evidence of conversion between:
 Aitken and accumulation SO42- ;
 Accumulation and dissolved SO42- ;
 DMS and dissolved SO42- ;
 Negative correlation of DMS not yet understood
 SO2 and dissolved SO42-
◦ More detailed chemical analysis is needed within PRECIS.
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PRECIS 1.7.1
MOSES 1
1961-1990 Sulfate Aitken mode
PRECIS 1.9.1
191
MOSES 2.2
16



Harrison R.M. (1999). Understanding Our Environment.
An Introduction to Environmental Chemistry and
Pollution Third Edition
Pollution.
Edition.
Andreae M.O; Jaeschke W.A. (2008). Northern Arizona
University.
y Atmospheric
p
Reactions of Sulfur and
Nitrogen. Available online:
http://jan.ucc.nau.edu/~doetqpp/courses/env440/env
440 2/lectures/lec37/lec37 htm last accessed 10th
440_2/lectures/lec37/lec37.htm,
September 2010.
Norris K. B. (2003). Dimethylsulfide Emission: Climate
Control by Marine Algae? Available online:
http://www.csa.com/discoveryguides/dimethyl/overvie
h llast accessed
d 10
hS
b 2010
w.php,
10th
September
2010.
17
Norbert Bonnici
Adam Gauci
Pierre-Sandre Farrugia
Louis Zammit Mangion
Simon Tucker
Chloe Morrell
David Hein
David Hassell
http://precis.metoffice.com/
18
James Ciarlo`
C l `
E: jcia0004@um.edu.mt
j
Noel Aquilina
E
l
ili @
d
t
E: noel.aquilina@um.edu.mt
T: +356 2340 3036
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