Institut für Physik der Atmosphäre Flight facility Oberpfaffenhofen

1. 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 http://www.pa.op.dlr.de/aerosol/astar2007/ http://www.pa.op.dlr.de/pazi-falcon/circle2/ Institut für Physik der Atmosphäre Flight facility Oberpfaffenhofen

2. ASTAR 2007 (Longyearbyen 25 Mars – 19 Avril)

3. The cloud in-situ measurements onboard the AWI Polar 2 aircraft ● 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) ● Nevzorov probe (AWI) : Liquid / ice water content ● AMALi (AWI) 355nm & 532nm (// & ^), Spectral Albedometer (Univ. of Mainz)

4. Overview of the observations ● 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)

5. Example of Polar 2 Flight plan and measurements (7 April 2007) C A Calipso track interception A C

6. Polar 2 flight mission CALIPSO Track NOAA 18 RGB Channel 10:10 UTC

7. In situ observations

8. 11:00 UT

9. 9:08 LT

10. Supercooled water Cloud top : -23°C Ice crystals Asymmetry parameter LWC (g/m3) Ice particle conc. (l-1) Effective diam. (um)

11. 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 mm PMS FSSP size distribution Theoretical scattering phase function (FSSP)

12. 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 mm g : 0.836 PMS FSSP size distribution Theoretical scattering phase function (FSSP) ● Measured scattering phasefunction (Polar Nephelometer)

13. Example of measurements below the cloud (precipitation) : FL 600 m / -13°C FSSP Polar Nephelometer CPI Ice particle conc : 10 l-1 Extinction : 2 km-1 IWC : 20 mg/m-3 Deff : 70 mm g : 0.775

14. CPI images obtained below the cloud (precipitation) 0 500 mm

15. 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 mm to 200 cm-3 / 11 mm). ●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, …)

16. CIRCLE-2 (Oberpfaffenhoffen 7 – 27 Mai)

17. The cloud in-situ measurements onboard the DLR Falcon aircraft ● 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)

18. Overview of the observations

19. Example of data obtained on 16 May B A

20. Altitudes need to be confirmed Point A Point B

21. Point A CALIPSO Point B FL 11400m / -56°C FL 11800m / -59°C

22. Extinction Coef. (PN). Scale 0 – 0.5 km-1 Point A Point B

23. 0 200 mm Ice crystals from CPI : Plate is the dominant shape but with no 22° Halo on PN ?

24. 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. 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 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.

25. 16 May FL 7000 m / -30°C • Oberpfaffenhofen to Brest flight 22° halo occurrence (when > 1) Halo No Halo

26. 22 ° Halo occurrence => pristine ice crystals 22° halo Extinction Coef. = 0.80 km-1 Asym. Parameter = 0.779

27. Smooth scattering phase function => Irregular shaped ice particles Ext. Coeff. = 0.35 km-1 Asym. Param. = 0.765

28. 26 MAY : Overpass CloudSat-1B_CPR RASTA (calibrated) Temporal Evolution ?

30. 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.