observation of a saharan dust outbreak on 1-2 august 2007: determination of microphysical particle...
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Observation of a Saharan dust outbreak on 1-2 August 2007: determination of microphysical particle parameters
Paolo Di Girolamo1, Donato Summa1, Rohini Bhawar1, Tatiana Di Iorio2, Marco Cacciani2, Igor Veselovskii3, Alexey Kolgotin3
1 DIFA, Università degli Studi della Basilicata, Potenza, Italy, 2 Dipartimento di Fisica, Università degli Studi di Roma “La Sapienza”, Roma, Italy
3 Physics Instrumentation Center, Troitsk, Moscow Region, Russia
6th COPS Workshop, 27 – 29 February 2008University of Hohenheim, Stuttgart
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020222018
Particle Backscatter Ratio at 1064 nm, 1-2 August 2007
1410 1612
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TIME (UTC)
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BASIL
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18:45
Water Vapour Mixing Ratio
1-2 August 2007
03:16TIME (UTC)
g/Kg
12
0
3.6
12000
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out-flow boundary
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Measured parameters:
• particle backscattering coeff. @ 355, 532 and 1064 nm 3 • particle extinction coeff. @ 355 and 532 nm 2• depolarization ratio @ 355 & 532 nm, • atmospheric temperature• water vapour mixing ratio • relative humidity from simultaneous measurements of
temperature and water vapor mixing ratio
BASIL Raman Lidar
Raman lidar measurements (25 May – 30 August 2007)
More than 500 hours of measurementsdistributed over 58 days
particle size and microphysical parameters
COPS Web Pagehttp://www.cops2007.de/
Operational Products
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The retrieval scheme employs Tikhonov’s inversion with regularization
Algorithm developed at the Physics Instrumentation Center
Inversion algorithm
Particle size distribution parameters:Mean radius rmean
Effective radius reff
Number concentration NSurface concentration SVolume concentration VComplex refractive index mr and mi
Parameters of a bimodal size distribution
3 + 2
In the solution of the inverse problem, particle size distribution f(r) is approximated by the superposition of base functions Bj(r) as:
where cj(z) are the weight coefficients.
Base functions have a triangular shape on a logarithmic-equidistant grid
Veselovskii et al., Appl. Opt. 41, 3685–3699, 2002.
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Inversion with regularization
rmin=0.05 m, rmax=15 m
1.3 <mr< 1.6
0<mi<0.04
f(r)
Mean radius rmean
Effective radius reff
Number concentration NSurface concentration SVolume concentration V
numerically integrating f(r) over the radius interval [rmin, rmax]
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020222018
Particle Backscatter Ratio at 1064 nm, 1-2 August 2007
1410 1612
12000
TIME (UTC)
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Focus: two specific times when aerosol loading was higher21:00-21:30 UTC on 1 August 200700:00-00:30 UTC on 2 August 2007
(red dashed lines in figure)
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1 August 2007, 21:00-21:30 UTC 2 August 2007, 00:00-00:30 UTC
averaging layers
1710-2100 m 2100-2490 m2490-2910 m2910-3210 m 3690-4110 m 4110-4500 m 4500-4920 m5310-5700 m
400 m thick
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1 August 2007, 21:00-21:30 UTC 2 August 2007, 00:00-00:30 UTC
Particle size distribution
0.1 m <rmean< 0.2 m, 0.1 m <reff< 1.0 m5 m3/cm3 <V< 40 m3/cm3
Particle size distribution fine mode: 0.15-0.25 m
coarse mode: 1-4 m
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1.44 <mr< 1.530.003 <mi< 0.008
1500 2000 2500 3000 3500 4000 4500 5000 5500 60001.40
1.45
1.50
1.55
mR mI
Altitude
mR
0.000
0.001
0.002
0.003
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0.005
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mI
1 August 2007, 21:00-21:30 UTC
Method: Inversion with regularization, performed by generalized cross-validation. In this retrieval, the combination of particle extinction and backscatter coefficients becomes especially important.The number of backscatter coefficients in the retrieval procedure should exceed the number of extinction coefficients by a factor of 2–3.
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Backward trajectories ending at 00:00 UTC on 2 August 2007
NOAA-ARL HYSPLIT Lagrangian trajectory model
The air masses observed in Achern in the altitude region 3.5-5 km a.g.l. originated in the mixed layer over the Saharan desert
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21:30 01:1523:22
Particle Backscattering coefficient at 355nm (log scale)10000
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1-2 August 2007Dust particle hygroscopicity
22:00-23:00
3-5.5 km
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21:30 01:1523:22
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Relative Humidity1-2 August 2007
21:30
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22:00-23:00
3-5.5 km
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Particle backsc. coeff. at 355 nm vs RH, 1 August 07, 22:00-23:00 UTC, t=2min, 3-5.5 km
RH [%]
Par
ticl
e
bac
k 35
5 n
m [
m-1
sr-
1]
0 25 50 75 100
0
1.6x10-6
3.2x10-6
Substantial increase in particle backscattering when RH > 75 %
Swelling tendency of hygroscopic aerosol particles at large RH values
Trend compatible with partially soluble aerosol particles
Back-trajectories show that airmasses originated in the Saharan desert transited for several days over the Atlantic Ocean
Aged dust particles presumably mixed with maritime aerosol during the advection to the meaurement site and partially coated with hygroscopic material
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lidar dark bandfreezing level
radar bright band
freezing level
University of Manchester Radio Wind Profiler, 1290 MHz UHF Doppler radar
BASIL Raman Lidar
radar bright band
freezing level
MIRA 36, Radar Reflectvity at 36 GHz
radar bright band
freezing level
MIRA 36, Linear Depolarizatio Ratio
9 m/s4.5 m/s
4000
AL
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m)
radar bright band
freezing level
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10:46 11:37
Shear
IOP 9c – 20 July 07Passage of the frontal zone, with a Mesoscale Convective System inbedded
The waves like structures seen in the data just prior to the arrival of thethunderstorm are due to shear between inflow and outflow regions.
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Range corrected signals at 1064 nm
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21:00 04:0000:30
BASIL – Rhine Valley Supersite(Lat: 48.64 ° N, Long: 8.06 E, Elev.: 140 m)
25-26 July 2007 – Water vapour mixing ratiog/kg
1
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Hei
gh
t a.
s.l.
(m
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TIME (UTC) T = 5 min, z = 150 m
0.1 1 10
26 July 07
mixing ratio [g/kg]
RadioSonde 01:15 Lidar 01:15-01:25
mixing ratio (g/kg)
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10:46 11:37 10:46 11:37
Range corrected signals at 1064 nm Water vapour mixing ratio
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1064 532 355
355 532
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Particle Backscatter Ratio at 1064 nm
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Particle Backscatter Ratio at 532 nm
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1500 2000 2500 3000 3500 4000 45000.0
0.1
0.2
0.3
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0.5
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0.8
r
(m
)
Altitude (m)
reff
rmean
1-D approach
2-D approach
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mR