Properties and radiative
effects of desert dust in
the Mediterranean
A. di Sarra 23/10/2014
radiation budget
surface energy budget
photochemistry
heterogeneous chemistry
air quality/health
fertilization
atmospheric thermal structure/dynamics
cloud properties
…
Nabat et al., 2013
Israelevich et al., 2012
MODIS data, 2001-2010
Moulin et al., 1998
METEOSAT, 1994
30 March 2013
MODIS-Terra
1000 mb
850 mb
1000 mb
850 mb
29 July 2005
MODIS-Terra
Hamonou et al., 1999
non-dust
dust
1999-2008
Di Iorio et al., 2009
Pey et al., 2013
Pey et al., 2013
Becagli et al., 2012
Summer
Winter
Marine Boundary Layer
MBL
Courtesy of S. Becagli
Boundary Layer
over land
Radiative forcing
ΔF = Fn,s – Fn
Refractive index
Size
Shape
REFRACTIVE INDEX
Formenti et al., 2011
Scheuvens et al., 2013
REFRACTIVE INDEX
Di Biagio et al., 2014
SIZE DISTRIBUTION
Denjean et al., 2013
22 and 28 June 2013: Transport
from Tunisia to Lampedusa
22 june 2013, F35-36
6000
Dust
aerosols
5000
Altitude (m)
6000
4000
5000
3000
4000
F38
2000
3000
dV
dlogDp
1000
2000
10000
0
20
40
60
0
20
40
60
0
6000
0
5000
10000 1
0
5000
10000 1
28 june
2013,
F38-39
10
10
Altitude
(m) (m)
Altitude
6000
5000
700nm
550nm
450nm
5000
4000
F35
grimm lisa
grimm
uhsas lisa
uhsas
fssp
fssp
grimm lamp
grimm
grimm lamp
cnrm
grimm cnrm
4000
3000
Dust
aerosols
3000
2000
2000
1000
dV
dlogDp
1000
0
0 0
0
10
20
30 0
500 10001500
1
10
20
30 0
500 10001500
1
Scat. coeff.
(Mm-1)
Numb. conc.
(#.cm-3)
10
10
Diameter
(µm)
 Similar dust source and days
of transport but different
mixing state
SIZE DISTRIBUTION
Zhao et al., 2013
SHAPE
Haanpanala et al., 2012
Surface direct radiative forcing
VERTICAL DISTRIBUTION
Gomez Amo et al., 2010
(HL-ABL)/HL (%)
surface
-13
toa
16
atm
-22
(HL-SBL)/HL (%)
surface
11
toa
-13
atm
17
Papadimas et al., 2012
All-sky
clear-sky
DRE TOA SW
-10 0
DRE ATM SW
0 20
DRE SRF SW
2000-2007
-10 0
Mueller et al., 2012
SAMUM 2006
How to derive a correct estimate of the RF?
Satheesh and Ramanathan, 2000
Radiative forcing efficiency
PSP
Cimel
PIR
MFRSR
Surface aerosol FE: aerosol types
2004-2007
Di Biagio et al., 2010
Di Biagio et al., J. Geophys. Res., 2009
Aerosol FE at the top of the atmosphere
FETOA 
Di Biagio et al., 2010
d  ISW ,TOA 
d
Daily mean aerosol forcing efficiency
FES and FETOA at different θ  integrated to obtain the daily FE
FEd at the equinox (Wm-2)
TOA
Surface
Atm
DD
-45.5  5.4
-68.9  4.0
23.4  6.7
UI-BB
-19.2  3.3
-59.0  4.3
39.8  5.4
MA
-36.2  1.7
-94.9  5.1
58.7  5.4
FEd at the summer solstice (Wm-2)
TOA
Surface
Atm
DD
-47.3  5.6
-87.5  5.0
40.2  7.5
UI-BB
-23.3  4.1
-75.6  7.9
52.3  8.9
MA
-44.2  2.1
-120.5  6.5
76.3  6.8
The atmospheric forcing is ~30-50% of the surface forcing for DD,
Di Biagio et al., 2010
~70% for UI-BB, and ~60% for MA.
Daily mean aerosol radiative forcing
The daily mean radiative forcing
(RFd) at TOA and at the surface are
largest for DD due to the high value of
both FEd and average τ.
The atmospheric RFd, conversely, is
approximately independent of the
aerosol type.
RFd =FEd  
March 26, 11:50 UT
MODIS-TERRA
March 26, 2010
March 28, 11:50 UT
MODIS-TERRA
March 28, 2010
MFRSR
max 1.88
<0.09
PSP and PIR radiometers
instantaneous, at 35° solar zenith angle, LW, SW, and total forcing, for 26
March, 2010.
SW: observations on two days, surface + CERES
LW: RT model + observations at the surface and CERES
On a daily basis: surface LW RF is about 50% of the SW
TOA LW RF is about 40% of the SW
a bout 75% of the SW atmospheric RF is compensated
by the LW RF
di Sarra et al., 2011
9:35 UTC
MODIS
22 May 2013
12:50 UTC
MODIS
22 May 2013
Lampedusa
22 May, 12:57 UT
Sky Imager
22 May, 12:50 UT
23 May, 13:46 UT
Sky Imager
20 May, 12:50 UT
SW: Observations
LW: Observations + MODTRAN 4.3 calculations
Forcing efficiencies
SW, global
SW, diffuse
LW
LW/SW
-136 W/m2
+257 W/m2
+33 W/m2
24%
instantaneous values!!
Over a whole daily cycle
FEd~FE/2 in the SW
LW/SW
~50%
(di Sarra et al., 2011)
Gomez Amo et al., 2014
Meloni et al., 2014
Ground-based and Airborne Measurements of the Aerosol Radiative Forcing (GAMARF)
2008
Meloni et al., 2014
Meloni et al., 2014
• Vertical distribution
• Optical properties
• LW effects
Recommendation:
Closure with respect to high quality radiation
measurements
Thank you
Pace et al., 2012
Red – 2009
Black – 2011
Green - 2010
Blue -2012
2.0
1.6
Pace et al., 2006

1.2
0.8
0.4
0.0
-0.4
0.0
0.2
0.4
0.6

0.8
1.0
1.2
Meloni et al., 2004
JULY 14 2002
Lidar backscatter ratio
JULY 16 2002
HYSPLIT transport and dispersion model from the NOAA Air Resources
Laboratory (ARL)
AOD (500 nm)
= 0.227
14 July
α = 0.080
δ = 0.46-0.56
16 July
α = 0.698
δ = 0.25-0.47
Meloni et al., 2004
MISR + MFRSR
Meloni et al., 2004
Best match (minimum RMDS) wavelength-independent SSA and g
14 July
SSA = 0.97 g = 0.80
16 July
SSA = 0.88 g = 0.81
INSTANTANEOUS AEROSOL RADIATIVE FORCING EFFICIENCY
(RF per unit AOD at 500 nm)
AT 400-700 nm
Day
14/07/2002
16/07/2002
0
0.96
0.97
0.88
0.89
g
0.79
0.80
0.81
0.82
Instantaneous RFE (W m-2)
surface
TOA
-39.3
-17.3
-44.2
-20.1
-73.2
-5.1
-79.0
-7.4
7 September 2005
di Sarra et al., 2013