Arctic Ice Clouds and their Interactions with aerosols

Éric Girard, UQAM

• Research interests and recent work• My contribution to NETCARE• What is currently needed to go forward?

NETCARE First Workshop, November 18-19th 2013, U. of Toronto

My research interests

• Modeling of ice clouds and mixed-phase clouds.

• Interactions between highly acidic aerosols and Arctic clouds and radiation (dehydration-greenhouse feedback). Investigated using in-situ obs, remote sensing and modeling.

Ice and Snow layers

Hypothesis

Dehydration Greenhouse Feedback (DGF)

Less H2O vapour

Acid Aerosols **

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**Low Acid AerosolsHydrophilic

warmercolder

Reduction of the greenhouse effect

Acidic coating on IN leads to the formation of fewer but largerice crystals (de-activation effect), which precipitate more efficiently. The airmass dehydrates

and the greenhouse effect decreases

Small cooling rate by IR cooling or by weak ascent

Thin Ice CloudsThin Ice Clouds type 1type 1Thin Ice Clouds Thin Ice Clouds type 2type 2

Cold Ice and Snow Surface

Recent work

• Observations: Analysis of ISDAC ice cloud cases and their relationship to aerosols

• Observations: Remote sensing and backtrajectory analysis

• Modeling: Ice cloud simulations and parameterizations of ice nucleation (e.g. UBC lab studies)

Table 2: Table of temporal and spatial coordinates of the profiles of ice clouds selected by the algorithm of table 1 and for which the cloud temperature drops below -30±0.5°C, during the ISDAC measurement campaign.

ISDAC flights

Observations: Analysis of ISDAC ice cloud cases and their relationship to aerosols

Observations: Remote sensing and backtrajectory analysis

Figure 3: Averaged IWC (a), Nic (b) and Rei (c) versus RHIce over each 2% period. And RHIce versus Ta over each 2.5°C period, with standard deviation associated for ice clouds defined in the Table 2.

a) b)

c) d)

Jouan et al. (JGR,2012)

31/0313:50

30/0313:12

B1 B2

Figure 8 : Calipso track sections (line) and FLEXPART air mass positions (*) along FLEXPART trajectories initialized in the boxes B1 and B2 of Figure 7. The color scale indicates the elapsed time in hours between the CALIPSO observation and the aircraft observation.

Figure 9 : Dardar Mask track section observed on March 31th (a) at 13:48 UTC and on March 30th (b) at 13:05, 2008 from of the synergistic Cloudsat radar and CALIPSO lidar.

AL-1 CL-1AL-2

Jouan et al. (ACPD, 2013)

Until recently, parameterizations of ice nucleation were based on limited field studies. Empirical relationships between the IN concentration and T and Si were derived.

From Meyers et al. (1992)

Objective: Implement more physically-based IN parameterizations based on aerosol physico-chemical properties.

Eastwood et al. (2009)

Modeling: Ice cloud simulations and parameterizations of ice nucleation (e.g. UBC lab studies)

Aerosol scenarios and simulated flights

Scenario Authors IN Contact angle

NAT1 Eastwood et al, 2008 uncoated θ = 12o

NAT2 Eastwood et al, 2008 uncoated θ → P(θ)

AC Eastwood et al. 2009 Acidic θ = 26o

ORI Meyer et al, 1992 --------- ---------

# Vol Date Time Location Air mass TIC

F12 April 5th, 2008 01:15:35 - 01:34:05 Barrow - (203.364 ; 71.286) Pristine TIC-1

F13 April 5th, 2008 20:35:26 - 21:00:05 Barrow – (203.213 ; 71.259) Pristine TIC-1

F21 April 15th, 2008 00:55:40 - 01:17:24 Barrow - (203.201 ; 71.334) Pollué TIC-2

F29 April 29th, 2008 04:08:22 - 04:27:51 Fairbanks - (208,329 ; 64.727) Pollué TIC-2

Meyers et al. 1992 is an empirical relationship and does not account for solution coating.AC, NAT1 and NAT2 are based on lab experiment. The contact angle is used to differentiate acid-coated and uncoated IN in the classical nucleation theory.

Lab studies and modeling

10

Ni (simulated) vs Ni (obs): unpolluted air mass (F12 and F13)

Bias: +32 L-1 Bias: -187 L-1

New parameterization Original parameterization

Breau-Roussel and Girard (JGR, 2013)

Ni (simulated) vs Ni (obs): polluted air mass (F21 and F29)

New parameterization Original parameterization

Bias: +9 L-1

Bias: +9 L-1

Lab studies and modeling

Breau-Roussel and Girard (JGR, 2013)

Acid coating on IN and its impact on the Arctic climate

Girard et al. (Int. J. Clim., 2013)

~ -3K

Mixed-phase clouds observed during SHEBA

Du et al. (Atmos. Res., 2011)

My contribution to NETCARE

1. Implement new ice nucleation parameterizations already existing or to be developed with NETCARE observations. In addition to the CNT approach, singular hypothesis will be tested. Other parameterizations from CFDC observations, aerosols collected in the field tested in lab and “pure” aerosols tested in lab will also be implemented. Test and validate these parameterizations against already available observations (e.g. ISDAC) and new observations from NETCARE.

2. Couple GEM to the ECMWF Aerosol Reanalysis (ECMWF-MACC) and test this new version with the new parameterizations. A comparison with the fully coupled version of GEM (GEM-MACH) and/or with GEM-CAM is also possible.

3. The new version of the model will be used to perform pan Arctic simulations of the effect of acid coating on Arctic clouds and radiation.

What is currently needed to go forward?

1. We need to relate the atmospheric IN chemical composition and their ice nucleation ability in both types of ice clouds.

2. Immersion of unactivated haze droplets and deposition nucleation are important to better understand for the simulation of ice clouds.

Sulphate emission and transport

AMAP Assessment Report: Arctic Pollution Issues. Arctic Monitoring and Assessment Programme (AMAP), Oslo, Norway. Xii+859 pp

Arctic haze: the Arctic can be very polluted during winter

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