Eric Girard. Invited Professor (Sept 16 to Apr 17) IPSL/LATMOS/LMD/UPMC/École Polytechnique, Paris, France

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1 Importance of chemical composition of Ice Nuclei on the Formation of Arctic Ice Clouds and Cloud Radiative Forcing Eric Girard Département des sciences de la Terre et de l atmosphère Centre pour l Étude et la Simulation du Climat à l Échelle Régionale (ESCER) Université du Québec à Montréal, Qc Canada Invited Professor (Sept 16 to Apr 17) IPSL/LATMOS/LMD/UPMC/École Polytechnique, Paris, France 1

2 OUTLINE INP deactivation effect and Polar Night Observed and simulated ice clouds during ISDAC Simulated radiative forcing over the Arctic of the INP deactivation effect Summary 2

3 Deactivation effect 1/4 IPCC,

4 Aerosol indirect radiative effects Deactivation effect 2/4 Shortwave/Infrared Infrared IR cooling rate Optical depth Ice crystals (ice clouds) Glaciation of ice cloud Adapted from Isaksen et al. (2009) Polar night 4

5 Hypothesis INP Deactivation Effect and Infrared Cooling Acidic coating on IN leads to the formation of fewer but largerice crystals (deactivation effect), which precipitate more efficiently. The airmass dehydrates and the Thin Ice Clouds type 2 Small cooling rate by IR cooling or by weak ascent * * * Low Acid Aerosols * * * * * * * * * * * * * * * Hydrophilic * * * * Acid Aerosols * * * * * * * * * * * * * * Less H 2 O vapour colder greenhouse effect decreases Reduction of the greenhouse effect warmer Ice and Snow layers Thin Ice Clouds type 1 Deactivation effect 3/4 Blanchet et Girard, Nature, 1994 Girard, Ph.D. Thesis, McGill U., 1999 Cold Ice and Snow Surface 5

6 Deactivation effect 4/4 TICs, Types of Ice Clouds TIC-1: Large concentration (~100 à 1000 L -1 ) of small ice crystals (< ~30 mm). Seen by lidar but not by radar. TIC-2: Small concentration (< ~50 L -1 ) of precipitating crystals (~ 100 mm) crom cloud top to cloud base. Seen by lidar et radar. Why 2 TICs? The deactivation effect of INPs could be responsible. 6

7 Deactivation effect: Observations 1/4 Jouan et al.(2012; 2014): OBSERVATIONS OF TIC-1 AND TIC-2 DURING ISDAC Date Flight number Place Flight Type DeltaT Ice cloud (HHMMSS) H2Oliq Presence inside Ice Cloud MP cloud Presence in Lower-Layers 01/04/08 9 Barrow Descent Spiral 23:14:00 23:31:30 No Yes F9 04/04/08 11 Barrow Descent Spiral 19:33:30 19:51:00 No Yes F11 05/04/08 12 Barrow Ascent Spiral 01:21:00 01:33:30 No No F12 05/04/08 13 Fairbanks Ascent Rampe 17:40:30 17:59:30 Yes Yes F /04/08 13 Barrow Descent Spiral 19:18:00 19:37:30 Yes Yes F /04/08 13 Barrow Descent Spiral 20:35:30 20:55:00 Yes Yes F /04/08 14 Barrow Descent Spiral 23:07:00 23:23:00 Yes Yes F14 08/04/08 15 Fairbanks Ascent Rampe 15:00:30 15:16:00 No No F15 14/04/08 20 Barrow Descent Spiral 19:51:30 20:14:00 Yes No F20 15/04/08 21 Barrow Ascent Spiral 00:55:30 01:16:00 Yes No F21 19/04/08 24 Barrow Ascent Rampe 01:23:30 01:41:30 Yes Yes F24 25/04/08 29 Barrow Ascent Rampe 02:27:00 02:38:30 No Yes F29 Code Objective: Characterize TIC-1 and TIC-2 in terms of concentration and size of crystals, temperature and humidity. 7

8 Deactivation effect: Observations 2/4 a) IWC vs RH i b N i vs RH i ) TIC-1 TIC-2 c) d R i vs RH i ) RH i vs T 8 Jouan et al. (2012)

9 Deactivation effect: Observations 3/4 ISDAC case studies: April 1st (TIC-1) and 15th (TIC-2) Figure 7: Relative Humidity over ice as a function of Temperature for ice clouds F9 and F21. Data are averaged over each 30-s and 2.5- C period. Symbol size represent N ic,mean and the bar color represent the R ei,mean of ice crystals from the combinations 2 (2DS + 2DP). 9 Jouan et al. (JGR, 2012)

10 Deactivation effect: Observations 4/4 ISDAC case studies: April 1st (TIC-1) and 15th (TIC-2) AMS measurements on April 15 near Barrow during ARCPAC show a ammonium to sulfate ratio ~ 0.3 to 0.4. This indicates that aerosols were coated either with sulphuric acid or ammonium bi-sulphate. Jouan et al. (ACP, 2014) The TIC-2 observed on April 15th was clearly associated to highly acidic 10 aerosols.

11 Deactivation effect: Modelling 1/4 MODELLING APPROACH 11

12 Deactivation effect: Modelling 1/4 Ice nucleation on coated vs uncoated INPs Hoose et Möhler (2012) 12

13 Modelling of TICs observed during ISDAC (Keita et Girard, 2016) GEM Model at 2.5 km resolution with a domain centered over Alaska. 13

14 F12 - April 5th TIC-1 F29 - April 29th TIC-2 14

15 Deactivation effect: Modelling 1/4 F21 and F29 15

16 Radiative effect of TICs-2 (Girard et al., 2013) Deactivation effect: Radiative forcing 1/7 Model: GEM-LAM à 25 km horiz. resolution January and February 2007 Ensemble of simulations for each aerosol scenario Russia Europe Objective: Evaluate the radiative effect of TIC-2 (compared to TIC-1) for 2 winter months. Canada Aerosol scenario 1: Non coated INP (small contact angle) Aerosol scenario 2: Coated INPs (large contact angle) 16

17 LWP and IWP Anomalies Deactivation effect: Radiative forcing 2/ gm gm -2 17

18 RH i Anomaly at 850 hpa Deactivation effect: Radiative forcing 3/7 +10 à +13% 18

19 Precip Rate Relative Anomaly Deactivation effect: Radiative forcing 4/7 +~20% 19

20 Deactivation effect: Radiative forcing 5/7 DLR Anomaly at the surface -3 à -4 Wm -2 20

21 T Anomaly at the surface Deactivation effect: Radiative forcing 6/7-2 à -3 K 21

22 MSLP Anomaly Deactivation effect: Radiative forcing 7/7 ~ -3 hpa ~ +4 hpa 22

23 SUMMARY Observations and modelling suggest that the two types of ice clouds are linked to the INP chemical composition through their ice nucleation properties. Recently developed INP parameterizations seem to be able to simulate TICs-1 and TICs-2 assuming we know how to model properly the aerosol composition. Radiative effect of the INP deactivation effect during the polar night is substantial and reaches up to -4 W m- 2 and a cooling up to -3 K at the surface in our sensitivity study. 23

24 Thank your for your attention 24