overview of the data obtained during astar 2007 (arctic mixed-phase clouds) & circle-2...
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OVERVIEW OF THE DATA OBTAINED DURING ASTAR 2007 (ARCTIC MIXED-PHASE CLOUDS) &
CIRCLE-2 (MID-LATITUDE CIRRUS)
Alfons Schwarzenboeck, Guillaume Mioche, Christophe Gourbeyre, Jean – Francois Fournol, Guy Febvre,
Jean – François Gayet
Institut für Physik der Atmosphäre
Flight facility Oberpfaffenhofen
http://www.pa.op.dlr.de/aerosol/astar2007/
http://www.pa.op.dlr.de/pazi-falcon/circle2/
ASTAR 2007
(Longyearbyen 25 Mars – 19 Avril)
● Cloud Particle imager (CPI) : High resolution measurement of the cloud particle shape (2.3 µm pixel size)
● Polar Nephelometer (PN) : Measurement of the scattering phase function of the cloud particles (3 µm < D < ~ 1 mm)
● PMS FSSP-100 or 2D-C probes : Particle size distribution (and shape) of particles (3 µm < d < 800µm)
The cloud in-situ measurements onboard the AWI Polar 2 aircraft
● Nevzorov probe (AWI) : Liquid / ice water content
● AMALi (AWI) 355nm & 532nm (// & ^), Spectral Albedometer (Univ. of Mainz)
Overview of the observations
DateTake-off
time(UT)
Landing Time(UT)
Observations Cloud types
2 April 14:45 17:00 Cloud observationsMixed-phase
stratiform cloud
3 April 11:55 14:45 Cloud observationsMixed-phase
stratiform cloud
7 April 8:20 11:30 CALIPSO (cloud) validationMixed-phase
stratiform cloud
8 April 9:15 12:15Alternate Remote sensing/ Cloud
observationsMixed-phase
stratiform cloud
9 April 8:15 11:20Alternate Remote sensing/ Cloud
observationsCALIPSO (cloud validation)
Mixed-phase stratiform cloud
10 April 11:00 14:00Alternate Remote sensing/ Cloud
observationsMixed-phase
stratiform cloud
14 April 11:45 14:30Alternate Remote sensing/ Cloud
observationsCirrus layer
14 April 15:50 17:50Alternate Remote sensing/ Cloud
observationsCirrus layer
16 April 8:30 11:30Cloud observations
CALIPSO (cloud validation)Mixed-phase
stratiform cloud
● 7 flights are related to mixed-phase stratocumulus clouds including 3 flights coordinated with the CALIPSO trace, and 2 flights are related to cirrus layers.
● Remote sensing observations concern AMALi Lidar (AWI) and Albedometer (Univ. of Mainz)
Calipso track interception
A
A
C
C
Example of Polar 2 Flight plan and measurements (7 April 2007)
NOAA 18 RGB Channel
10:10 UTC
CALIPSO Track
Polar 2 flight mission
In situ observations
11:00 UT
9:08 LT
Asymmetry parameter LWC (g/m3)
Ice particle conc. (l-1) Effective diam. (um)
Supercooled water
Ice crystals Cloud top : -23°C
Conc : 50 cm-3 Ext : 20 km-1 LWC : 0.14 g/m3 Deff :17.5 m
PMS FSSP size distribution Theoretical scattering phase function (FSSP)
Example of measurements in water cloud : FL 1450 m / -20°C
Conc : 50 cm-3 Ext : 20 km-1 LWC : 0.14 g/m3 Deff :17.5 m
g : 0.836
PMS FSSP size distribution Theoretical scattering phase function (FSSP)
● Measured scattering phase function (Polar Nephelometer)
Example of measurements in water cloud : FL 1450 m / -20°C
Example of measurements below the cloud (precipitation) : FL 600 m / -13°C
Polar Nephelometer CPI
FSSP
Ice particle conc : 10 l-1
Extinction : 2 km-1
IWC : 20 mg/m-3
Deff : 70 m
g : 0.775
0 500 m
CPI images obtained below the cloud (precipitation)
Conclusions and outlook
● Several mixed-phase stratocumulus clouds have been observed with similar properties, i.e. supercooled water droplets in the upper layer (of a few hundred meters depth) with ice crystals precipitating down to the surface.
● The cloud top layers varied between 1000 m / -15°C and 2000 m / -23°C
● The water - ice partition was observed with different magnitude. Furthermore different supercooled water-droplet properties were evidenced (50 cm-3 / 18 m to 200 cm-3 / 11 m).● Two Polar-2 flights has been devoted for the validation of CALIPSO cloud-products with transects performed along the satellite trace including numerous cloud vertical profiles and a third flight was carried out very close to the satellite trace.
● Several vertical profiles are therefore available for the validation of the cloud products (level 2a, i.e. extinction coefficient, particle phase, effective diameter, …)
CIRCLE-2
(Oberpfaffenhoffen 7 – 27 Mai)
● Cloud Particle imager (CPI) : High resolution measurement of the cloud particle shape (2.3 µm pixel size).
● Polar Nephelometer (PN) : Measurement of the scattering phase function of the cloud particles (3 µm < D < ~ 1 mm).
● PMS FSSP-300 and 2D-C probes : Particle size distribution (and shape) of particles (1 µm < d < 1 mm).
● Lidar WALES (DLR) 532nm & 1064nm (// & ^), Spectral Albedometer (Univ. of Mainz)
The cloud in-situ measurements onboard the DLR Falcon aircraft
Date
Measurement period
Flight operation
Cloud typeCloudSat CALIPSO interception
In situ Probes
RALI
Coordinated Flight
F = FrenchG = GermanStart
Time(UTC)
End Time
(UTC)
13 May 11:00 14:40 Creil - CreilNo Ci -
ConvectionYES N/A OK NO (F)
14 May11:0016:00
14:4016:50
OP – LeipzigLeipzip - OP
Broken CiBroken Ci
YESNO
No CPINo CPI
N/A NO (G)
16 May08:0012:2016:50
10:0015:3018:30
OP – BrestBrest – Brest
Brest - OP
Frontal CiFrontal CiFrontal Ci
NOYESNO
OKOKOK
OK-
YES-
20 May 12:40 14:40 OP - OP Outflow Ci NO OK N/A NO (G)
20 May 12:40 14:40 Creil – Creil Broken Ci YES N/A OK NO (F)
22 May10:2014:30
13:4016:20
OP – EsbjergEsbjerg - OP
Frontal CiFrontal Ci
NONO
OKOK
N/A NO (G)
23 May08:30 12:1516:40
10:2015:2018:30
OP – BilbaoBilbao – Bilbao
Bilbao – OP
Outflow CiOutflow CiOutflow Ci
NOYESNO
OKOKOK
N/A NO (G)
25 May07:0011:2016:10
09:0015:0017:40
OP – BrestBrest – Brest
Brest - OP
Broken CiCi layer
Ouflow Ci
NOYESNO
OKOKOK
OK-
YES-
26 May 11:05 14:00 OP - OP Outflow Ci YES OKRASTA OK
NO LNG
- YES
-
Overview of the observations
A
B
Example of data obtained on 16 May
Point A Point B
Altitudes need to be confirmed
Point A CALIPSO Point B
FL 11800m / -59°C FL 11400m / -56°C
Point A Point B
Extinction Coef. (PN). Scale 0 – 0.5 km-1
Ice crystals from CPI : Plate is the dominant shape but with no 22° Halo on PN ?
0 200 m
Ice Particle concentration = 1.2 cm-3
Ice water content = 1.5 mg/m3
Extinction coefficient = 0.30 km-1
Effective diameter = 11 mm
Asymmetry parameter = 0.784
Measured phase function
Theoretical phase function (FSSP + Mie)
A smoothed scattering phase function is observed despite rather geometrical
shape of ice crystals (see CPI images). Therefore, the internal lattice structure of the crystals plays a dominant role on
optical properties.
• Oberpfaffenhofen to Brest flight
22° halo occurrence (when > 1)
Halo No Halo
16 May FL 7000 m / -30°C
22° halo
22 ° Halo occurrence => pristine ice crystals
Extinction Coef. = 0.80 km-1
Asym. Parameter = 0.779
Smooth scattering phase function => Irregular shaped ice particles
Ext. Coeff. = 0.35 km-1
Asym. Param. = 0.765
CloudSat-1B_CPR
RASTA(calibrated)
26 MAY : Overpass
Temporal Evolution ?
Conclusions and outlook
● Over 7 operational days, 15 flights have been carried out in various Cirrus clouds. 5 flights were perfectly co-ordinated with the CALIPSO overpasses including 3 flights also co-ordinated with the French SAFIRE Falcon.
● The observations address different cirrus types (optically thin to very dense) with extinction varying from about 0.15 km-1 to more than 5 km-1).
● The in situ cloud instruments worked well and a first evaluation of the data show an excellent coherence between the different observations.
● The ensemble of observations gathered during CIRCLE2 (Lidar WALES on board the DLR Falcon and RALI system onboard the SAFIRE Falcon) constitutes an unique material to get new insights in Cirrus interactions with radiation and for the Calipso, CloudSat and MSG validations.
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