OVERVIEW OF THE DATA OBTAINED DURING ASTAR 2007 (ARCTIC MIXED-PHASE CLOUDS) & CIRCLE-2 (MID-LATITUDE...

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/

http://www.dlr.de/

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


observationsCALIPSO (cloud validation)

Mixed-phase stratiform cloud


observationsMixed-phase

stratiform cloud


observationsCirrus layer


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.

OVERVIEW OF THE DATA OBTAINED DURING ASTAR 2007 (ARCTIC MIXED-PHASE CLOUDS) & CIRCLE-2 (MID-LATITUDE...

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