Novel observational constraints on aerosol-cloudinteractions combining active and geostationary satellites
ESA-JAXA EarthCare Science and Validation Workshop
13/11/2023
Philip Stier, Philipp Weiss, Will Jones
Atmospheric, Oceanic and Planetary Physics
Department of Physics
University of Oxford
Observational constraints on aerosol-cloud interactions
Philip StierAerosol-cloudinteractions
fromspace
Constraining clouds and their controls

Assumptions in satellite based assessments:
i. Aerosol optical depth (AOD) is suitable proxy for cloud condensation nuclei (CCN)
ii. Clear-sky aerosol optical depth is representative for CCN in updrafts
iii. Causal relationship between retrieved aerosol, clouds and precipitation
Observational constraints on aerosol-cloud interactions(Bellouin et al., Rev. Geophys, 2019)

Suitability of AOD as proxy for CCN
Correlation of 6h CCN and AOD from ECHAM-HAM climate model:Aerosol Extinction Coefficient
0.00000.00010.0002

Aerosol Extinction Coefficient
0.00000.00010.00021414101088Median Cloud Base

64200

Geopotential Height

12

Geopotential Height

12200 400 600 800
CCN0.2%−1.0 −0.5 0.00.5Vertical correlation: 0.98

Median Cloud Base

Vertical correlation: 0.8464200200 400 600 800
CCN0.2%−1.0 −0.5 0.0

1.00.5r(ln(CCN0.2%),ln(AOD))r(ln(CCN0.2%),ln(AEC))r(ln(RH),ln(AEC))r(ln(CCN0.2%),ln(AOD))r(ln(CCN0.2%),ln(AEC))r(ln(RH),ln(AEC))

r<0.5 for 55% of the globe
Observational constraints on aerosol-cloud interactions(Stier, ACP, 2016)

1.0

Suitability of AOD as proxy for CCN
Correlation of 6h CCN and AOD from ECHAM-HAM climate model:

Vertical information keyObservational constraints on aerosol-cloud interactions(Stier, ACP, 2016; c.f. Painemal et al., ACP, 2020)

Suitability of AOD as proxy for CCN
Correlation of 6h CCN and AOD from ECHAM-HAM climate model:

Not possible totest if AOD
representative
for CCN inupdrafts

Observational constraints on aerosol-cloud interactions(Stier, ACP, 2005, 2016)

Climate modelling

Observational constraints on aerosol-cloud interactions
Philip StierClimate modelling

Observational constraints on aerosol-cloud interactions
Philip StierNext generation climate modelling

Observational constraints
Constraining
on aerosol-cloudclouds
interactions
Philip StierNext generation climate modelling

clouds
Idealised Aerosol Constraining
effects in global
km-scale simulations
PhilipStier
Herbertet al.
(in prep)

Regional Effects: Amazon• Strong diurnal cycleof aerosol effects onconvection• Major challenge forsun-synchronous
observations• Synergy withgeostationary
observations

Idealised Aerosol effects in global km-scale simulations
Herbert et al. (in prep)

Observational constraints on the diurnal cycle
ESA Cloud CCI+:• Detection and tracking ofgrowing deep convective cores
and associated anvils fromSEVIRI & GOES-R in asemi-Lagrangian framework• Combination with ESA Cloud
CCI+ radiative flux product• Unique insights into diurnal
cycle of cloud radiative effects
Observational constraints on the diurnal cycle(Jones et al., AMT, 2023)

Observational constraints on the diurnal cycle
ESA Cloud CCI+:• Detection and tracking ofgrowing deep convective cores
and associated anvils from
SEVIRI & GOES-R in asemi-Lagrangian framework• Combination with ESA Cloud
CCI+ radiative flux product• Unique insights into diurnal
cycle of cloud radiative effectsObservational constraints on the diurnal cycle(Jones et al., in prep.)Next generation climate modelling

Aerosol-cloud interactions in global km-scale ICON(Philipp Weiss)Aerosol-cloud interactions in global km-scale ICON(Philipp Weiss)Aerosol-cloud interactions in global km-scale ICON(Philipp Weiss)

Conclusions
EarthCARE may have been delayed a little...
but could not be more timely!
• Expect major advances in observational
constraint on vertical distribution of CCN,
cloud dynamics and structure, hence
aerosol-cloud interactions• Advanced geostationary cloud and aerosol
products provide significant synergies, inparticular global ISCCP-NG• Emergence of global km-scale Earth systemmodels allows to study key climate processes
at processes level – and requires entirely
new ways of thinking…
Novel observational constraints on aerosol-cloud interactions
Philip Stier