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Clouds and aerosols: Understanding processes –informing modelsMike Harvey, NIWA, Wellington NZ
S. Hartery, P. Kuma, O. Morgenstern, R. Querel, V. Varma, Jonny Williams, A. McDonald
• An improved understanding of processes is required to adequately represent and model Clouds and Aerosols in the Southern Ocean region
• Observations are sparse, process understanding is incomplete • Here we look at 2 processes and review:
1/Background/history 2/ Results 3/ Model representation• Current Project Plans
Project personnel ESM/C&A: Adrian McDonald1, Olaf Morgenstern2, Roger Davies3, Mike Harvey2, Vidya Varma2, Jonny Williams2, Simon Parsons1, Alex Schuddeboom1, Peter Kuma1
4D drones: Wolfgang Rack1, Josh McCulloch1, Mike Harvey2, Richard Querel2
The Deep South Clouds and Aerosols
31 2
Model Radiation errors CMIP5 model clouds do not reflect enough sunlight over the Southern Ocean.
Ensemble mean error for CMIP5 models in shortwave radiation absorbed by the Earth System. Positive values indicate too much shortwave radiation absorbed at surface (Trenberth and Fasullo 2010).
Incl - IPCC AR5, 2013: Fig 9.5
Wm-2
What is underlying this problem?Candidates:• Model deficiencies in representing cloud microphysical processes, that can
affect both cloud radiative properties and lifetime that are linked to: Aerosol-Cloud Interactions (ACI)
• Model deficiencies in dynamical and convective processes and PBL parameterization
• Inadequate parameterisation of small sub-grid processes
What properties are specific to the Southern Ocean in ACI – 1/ Ice Nuclei 2/ Cloud Condensation Nuclei
Earth System variables (Jan 2016)
Small amount
Large amount
Seasonally small
Seasonally large
Southern Ocean – ice andmixed phase of water in clouds
Probability of cloud containing supercooled liquid water >-40°C McFarquhar et al. SOCRATES (Calipso)
Over the Southern Ocean, observations have shown a predominance of liquid water down to -20°C, a lower temperature than seen elsewhere
More liquid droplets~ brighter clouds
Bigg, 1973
Bigg & Hopwood, 1963
Role of aerosols (ACI) Ice Nuclei measurements
Very low ice nuclei numbers measured from Tangaroa 2015 in Ross Sea region, Antarctica
DeMott, PNAS 2016Sea spray aerosol as a unique source of ice nucleating particles
Proposed Source: organic exudates in sea-spray aerosol
CESM experiments:
Kay et al 2016Experiments with Tice and tuning glaciation temperature from -5°C to -20°C:
Zonal global mean ctl has excessive absorbed solar radiation over Southern ocean
e.g. ESM model experiments with cloud phase
2/ Role of aerosols - ACI Cloud condensation nuclei (CCN)
Aerosol
Cloud
0.01 0.1 1Diameter /µm
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
dN/d
log(
d) /c
m-3
East Antarctic Plateau 1990 / 91Butter Point, Antarctic Coast 1988Baring Head January 1993Pacific Free Troposphere 1987Extended Cape Grim SpectrumEquatorial Boundary Layer Tarawa, 1987Macquarie Island Sea Level (4 m/s wind) 1995Macquarie Is Sea Level (20 m/s wind) 1995
Measured size spectra (Active Scattering Aerosol Spectrometer Probe) ASASP-100X
Sea saltMass mode
AccumulationMode
AitkenMode
MH/NIWA + Cape Grim +Measurements – Aerosol at the surface in Antarctica with air blowing off the continent can contain less particles than in the mid-latitude free troposphere
Southern Ocean Cloud Experiment (SOCEX)
Seasonal cycles of cloud drop concentration (Nd) and CCN concentration over the Southern Ocean.
Nd data are derived from from MODIS (red), limited aircraft flights during winter and summer (black squares), and measurements at Cape Grim (Ayers and Gras 1991).
294 295 296 297θq /K
4.5
4.7
4.9
5.1
5.3
5.5
5.7
5.9
6.1
6.3
Q /g
kg-1
(a) SOCEX-1 flight 930716.a descent 1 sub-cloud
305.5 306.0 306.5 307.0 307.5 308.0 308.5θq /K
6.2
6.4
6.6
6.8
7.0
7.2
7.4
7.6
7.8
8.0
Q /g
kg-1
(b) SOCEX-2 flight 950201.a descent 2 sub-cloud
300.5 301.0 301.5 302.0 302.5 303.0 303.5θq /K
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.4
6.6
6.8
Q /g
kg-1
(c) SOCEX-2 flight 950208.b descent 1 sub-cloud
0 20 40 60 80 100 120 140 160 180 200
Number /cm-3
0
500
1000
1500
2000
Pre
ssu
re a
ltitu
de /
m
ASASPFSSP
(a) SOCEX-1 930716.a descent 1
0 20 40 60 80 100 120 140 160 180 200
Number /cm-3
0
500
1000
1500
2000
Pre
ssu
re a
ltitu
de /
m
ASASPFSSP
(b) SOCEX-2 950201.a descent 2
0 20 40 60 80 100 120 140 160 180 200
Number /cm-3
0
500
1000
1500
2000
Pre
ssu
re a
ltitu
de /
m
ASASPFSSP
(c) SOCEX-2 950208.b descent 1
Boundary layer aerosol-cloud soundings
Case studies from the Southern Ocean Cloud Experiment SOCEX (M Harvey)
Blue vertical lineMean in following figure
Grey: Cloud droplets in marine stratocumulus
Red: Aerosol
Aerosol profilediagram
“Paluch” mixingdiagram
CASE1: well-mixed winter
CASE2: poorly mixed summer
CASE3: well mixed summer
Representing aerosol through modal scheme GLOMAP-mode in GCM’sTwo-moment (mass and number) modal microphysicsComponents: Sulfate, sea-salt, black and organic carbonProcesses: nucleation, scavenging, deposition, condensation, coagulation, sulfur chemistry, ageing
Matt Woodhouse, CSIROCSIRO – NIWA collaboration using GLOMAP in meteorological context to look at marine aerosol sources in the SOAP experiment
Summary• Antarctic aerosol climatology and its sources have regionally specific
characteristics• Low IN numbers, low AOD, seasonally varying aerosol (biogenic source in
summer), high frequency of low clouds• Aerosol can strongly influence cloud and climate in the region through aerosol-
cloud interactions but the remoteness means this is sparsely observed• There are specific micro-physical aspects that need special consideration in
modelling cloud in the region• Remote sensing alone cannot determine all key physical and chemical
properties of the aerosol• Organic processes and aerosol have less well quantified role in nucleation and
nuclei properties (and are likely important in summer Southern waters)• Complexities and inherent variability in key components will guide thinking on
observation – model interaction
Southern Sulfur/Aerosol/Cloud StudiesEarly ANZ Antarctic aerosol observation 1960s - 1990SOCEX (1993-95) CCN, Aerosol-Cloud InteractionACE-1 (1995) ACI indirect effects on clouds
SOIREE (1999) Iron, plankton & DMS
SCHeMe (2000-02) nssCa, O3, SO4 aerosol
SAGE (2004) Iron, plankton & DMS
PtoP (2006) Precursors to Particles SOA, halogens
SOAP (2011-12) plankton, DMS, VOC, CN, CCN
RtoR (2016) Reef to Rainforest - coral symbionts to cloud properties, DMS, VOC, CN, CCN,
S-ACI-MEE (2018) TAN1802 Antarctic Marine Environment and Ecosystems voyage ACI
SOCRATES (2018) CCN, Aerosol-Cloud Interaction
CAPRICORN (2018): Clouds, Aerosols, Precipitation Radiation and atmospheric Composition Over the southeRN ocean
AcknowledgementsTAN 2015: Paul deMott1, Tom Hill1, Blake Hornblow2
SOCEX3: Jorgen Jensen, Reinout BoersSOAP: Cliff Law, Sarah Lawson3, Zoran Ristovski4, Luke Cravigan4 et al.GLOMAP: Matthew Woodhouse3
Colorado State Uni (1), Sir Peter Blake trust(2) CSIRO(3) QUT (4)
SOLAS Science Plan2015 - 2025
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