Publications by Philip Stier


The propagation of aerosol perturbations in convective cloud microphysics

Atmospheric Chemistry and Physics Discussions Copernicus Publications (2018)

M HEIKENFELD, B White, L Labbouz, P STIER


SALSA2.0: The sectional aerosol module of the aerosol-chemistry-climate model ECHAM6.3.0-HAM2.3-MOZ1.0

GEOSCIENTIFIC MODEL DEVELOPMENT 11 (2018) 3833-3863

H Kokkola, T Kuhn, A Laakso, T Bergman, KEJ Lehtinen, T Mielonen, A Arola, S Stadtler, H Korhonen, S Ferrachat, U Lohmann, D Neubauer, I Tegen, C Siegenthaler-Le Drian, MG Schultz, I Bey, P Stier, N Daskalakis, CL Heald, S Romakkaniemi


Remote Sensing of Droplet Number Concentration in Warm Clouds: A Review of the Current State of Knowledge and Perspectives.

Reviews of geophysics (Washington, D.C. : 1985) 56 (2018) 409-453

DP Grosvenor, O Sourdeval, P Zuidema, A Ackerman, MD Alexandrov, R Bennartz, R Boers, B Cairns, JC Chiu, M Christensen, H Deneke, M Diamond, G Feingold, A Fridlind, A Hünerbein, C Knist, P Kollias, A Marshak, D McCoy, D Merk, D Painemal, J Rausch, D Rosenfeld, H Russchenberg, P Seifert, K Sinclair, P Stier, B van Diedenhoven, M Wendisch, F Werner, R Wood, Z Zhang, J Quaas

The cloud droplet number concentration (N d) is of central interest to improve the understanding of cloud physics and for quantifying the effective radiative forcing by aerosol-cloud interactions. Current standard satellite retrievals do not operationally provide N d, but it can be inferred from retrievals of cloud optical depth (τ c) cloud droplet effective radius (r e) and cloud top temperature. This review summarizes issues with this approach and quantifies uncertainties. A total relative uncertainty of 78% is inferred for pixel-level retrievals for relatively homogeneous, optically thick and unobscured stratiform clouds with favorable viewing geometry. The uncertainty is even greater if these conditions are not met. For averages over 1° ×1° regions the uncertainty is reduced to 54% assuming random errors for instrument uncertainties. In contrast, the few evaluation studies against reference in situ observations suggest much better accuracy with little variability in the bias. More such studies are required for a better error characterization. N d uncertainty is dominated by errors in r e, and therefore, improvements in r e retrievals would greatly improve the quality of the N d retrievals. Recommendations are made for how this might be achieved. Some existing N d data sets are compared and discussed, and best practices for the use of N d data from current passive instruments (e.g., filtering criteria) are recommended. Emerging alternative N d estimates are also considered. First, new ideas to use additional information from existing and upcoming spaceborne instruments are discussed, and second, approaches using high-quality ground-based observations are examined.


How Well Can We Represent the Spectrum of Convective Clouds in a Climate Model? Comparisons between Internal Parameterization Variables and Radar Observations

JOURNAL OF THE ATMOSPHERIC SCIENCES 75 (2018) 1509-1524

L Labbouz, Z Kipling, P Stier, A Protat


Anthropogenic aerosol forcing – insights from multi-estimates from aerosol-climate models with reduced complexity

Atmospheric Chemistry and Physics Discussions Copernicus Publications (2018)

S Fiedler, S Kinne, WTK Huang, P Räisänen, D O'Donnell, N Bellouin, P STIER, J Merikanto, TV Noije, K Carslaw, R Makkonen, U Lohmann


Quantifying the Effects of Horizontal Grid Length and Parameterized Convection on the Degree of Convective Organization Using a Metric of the Potential for Convective Interaction

Journal of the Atmospheric Sciences 75 (2018) 425-450

BA White, AM Buchanan, CE Birch, P Stier, KJ Pearson


The chemistry-climate model ECHAM6.3-HAM2.3-MOZ1.0

GEOSCIENTIFIC MODEL DEVELOPMENT 11 (2018) 1695-1723

MG Schultz, S Stadtler, S Schroeder, D Taraborrelli, B Franco, J Krefting, A Henrot, S Ferrachat, U Lohmann, D Neubauer, C Siegenthaler-Le Drian, S Wahl, H Kokkola, T Kuehn, S Rast, H Schmidt, P Stier, D Kinnison, GS Tyndall, JJ Orlando, C Wespes


On the Limits of CALIOP for Constraining Modeled Free Tropospheric Aerosol

GEOPHYSICAL RESEARCH LETTERS 45 (2018) 9260-9266

D Watson-Parris, N Schutgens, D Winker, SP Burton, RA Ferrare, P Stier


The aerosol-climate model ECHAM6.3-HAM2.3: Aerosol evaluation

Geoscientific Model Development Discussions Copernicus Publications (2018)

I Tegen, D Neubauer, S Ferrachat, C Siegenthaler-Le Drian, I Bey, N Schutgens, P STIER, D WATSON-PARRIS, T Stanelle, H Schmidt, S Rast, H Kokkola, M Schultz, S Schroeder, N Daskalakis, S Barthel, B Heinold, U Lohmann


Limited impact of sulfate-driven chemistry on black carbon aerosol aging in power plant plumes

AIMS Environmental Science 5 (2018) 195-215

M Z. Markovic, A E. Perring, R-S Gao, J Liao, A Welti, N L. Wagner, I B. Pollack, A M. Middlebrook, T B. Ryerson, M K. Trainer, C Warneke, J A. de Gouw, D W. Fahey, P Stier, J P. Schwarz


How Well Can We Represent the Spectrum of Convective Clouds in a Climate Model? Comparisons between Internal Parameterization Variables and Radar Observations

Journal of the Atmospheric Sciences American Meteorological Society (2018)

L Labbouz, Z Kipling, P Stier


THE GLOBAL AEROSOL SYNTHESIS AND SCIENCE PROJECT (GASSP): Measurements and Modeling to Reduce Uncertainty

BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY 98 (2017) 1857-1877

CL Reddington, KS Carslaw, P Stier, N Schutgens, H Coe, D Liu, J Allan, J Browse, KJ Pringle, LA Lee, M Yoshioka, JS Johnson, LA Regayre, DV Spracklen, GW Mann, A Clarke, M Hermann, S Henning, H Wex, TB Kristensen, WR Leaitch, U Poeschl, D Rose, MO Andreae, J Schmale, Y Kondo, N Oshima, JP Schwarz, A Nenes, B Andersrson, GC Roberts, JR Snider, C Leck, PK Quinn, X Chi, A Ding, JL Jimenez, Q Zhang


Aerosols at the poles: an AeroCom Phase II multi-model evaluation

ATMOSPHERIC CHEMISTRY AND PHYSICS 17 (2017) 12197-12218

M Sand, BH Samset, Y Balkanski, S Bauer, N Bellouin, TK Berntsen, H Bian, M Chin, T Diehl, R Easter, SJ Ghan, T Iversen, A Kirkevag, J-F Lamarque, G Lin, X Liu, G Luo, G Myhre, T van Noije, JE Penner, M Schulz, O Seland, RB Skeie, P Stier, T Takemura, K Tsigaridis, F Yu, K Zhang, H Zhang


On the spatio-temporal representativeness of observations

Atmospheric Chemistry and Physics European Geosciences Union (EGU) (2017)

NJ Schutgens, S Tsyro, E Gryspeerdt, D Goto, N Weigum, M Schulz, P Stier


Constraining the instantaneous aerosol influence on cloud albedo.

Proceedings of the National Academy of Sciences of the United States of America 114 (2017) 4899-4904

E Gryspeerdt, J Quaas, S Ferrachat, A Gettelman, S Ghan, U Lohmann, H Morrison, D Neubauer, DG Partridge, P Stier, T Takemura, H Wang, M Wang, K Zhang

Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from aerosol-cloud interactions (RFaci), a component of the total or effective radiative forcing. Because aerosols serving as cloud condensation nuclei can have a strong influence on the cloud droplet number concentration (Nd ), previous studies have used the sensitivity of the Nd to aerosol properties as a constraint on the strength of the RFaci. However, recent studies have suggested that relationships between aerosol and cloud properties in the present-day climate may not be suitable for determining the sensitivity of the Nd to anthropogenic aerosol perturbations. Using an ensemble of global aerosol-climate models, this study demonstrates how joint histograms between Nd and aerosol properties can account for many of the issues raised by previous studies. It shows that if the anthropogenic contribution to the aerosol is known, the RFaci can be diagnosed to within 20% of its actual value. The accuracy of different aerosol proxies for diagnosing the RFaci is investigated, confirming that using the aerosol optical depth significantly underestimates the strength of the aerosol-cloud interactions in satellite data.


Strong constraints on aerosol-cloud interactions from volcanic eruptions.

Nature 546 (2017) 485-491

FF Malavelle, JM Haywood, A Jones, A Gettelman, L Clarisse, S Bauduin, RP Allan, IHH Karset, JE Kristjánsson, L Oreopoulos, N Cho, D Lee, N Bellouin, O Boucher, DP Grosvenor, KS Carslaw, S Dhomse, GW Mann, A Schmidt, H Coe, ME Hartley, M Dalvi, AA Hill, BT Johnson, CE Johnson, JR Knight, FM O'Connor, DG Partridge, P Stier, G Myhre, S Platnick, GL Stephens, H Takahashi, T Thordarson

Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets-consistent with expectations-but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around -0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.


Dynamic subgrid heterogeneity of convective cloud in a global model: Description and evaluation of the Convective Cloud Field Model (CCFM) in ECHAM6-HAM2

Atmospheric Chemistry and Physics 17 (2017) 327-342

Z Kipling, P Stier, L Labbouz, T Wagner

© 2017 The Author(s). The Convective Cloud Field Model (CCFM) attempts to address some of the shortcomings of both the commonly used bulk mass-flux parameterisations and those using a prescribed spectrum of clouds. By considering the cloud spectrum as a competitive system in which cloud types interact through their environment in competition for convective available potential energy (CAPE), the spectrum is able to respond dynamically to changes in the environment. An explicit Lagrangian entraining plume model for each cloud type allows for the representation of convective-cloud microphysics, paving the way for the study of aerosol-convection interactions at the global scale where their impact remains highly uncertain. In this paper, we introduce a new treatment of convective triggering, extending the entraining plume model below cloud base to explicitly represent the unsaturated thermals which initiate convection. This allows for a realistic vertical velocity to develop at cloud base, so that the cloud microphysics can begin with physically based activation of cloud condensation nuclei (CCN). We evaluate this new version of CCFM in the context of the global model ECHAM6-HAM, comparing its performance to the standard Tiedtke-Nordeng parameterisation used in that model. We find that the spatio-temporal distribution of precipitation is improved, both against a climatology from the Global Precipitation Climatology Project (GPCP) and also against diurnal cycles from the Tropical Rainfall Measurement Mission (TRMM) with a reduced tendency for precipitation to peak too early in the afternoon. Cloud cover is quite sensitive to the vertical level from which the dry convection is initiated, but when this is chosen appropriately the cloud cover compares well with that from Tiedtke-Nordeng. CCFM can thus perform as well as, or better than, the standard scheme while providing additional capabilities to represent convective-cloud microphysics and dynamic cloud morphology at the global scale.


Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability.

Proceedings of the National Academy of Sciences of the United States of America 113 (2016) 5804-5811

S Ghan, M Wang, S Zhang, S Ferrachat, A Gettelman, J Griesfeller, Z Kipling, U Lohmann, H Morrison, D Neubauer, DG Partridge, P Stier, T Takemura, H Wang, K Zhang

A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud radiative forcing. Those processes are manifest in a number of relationships that can be expressed as factors dlnX/dlnY driving aerosol effects on cloud radiative forcing. These factors include the relationships between cloud condensation nuclei (CCN) concentration and emissions, droplet number and CCN concentration, cloud fraction and droplet number, cloud optical depth and droplet number, and cloud radiative forcing and cloud optical depth. The relationship between cloud optical depth and droplet number can be further decomposed into the sum of two terms involving the relationship of droplet effective radius and cloud liquid water path with droplet number. These relationships can be constrained using observations of recent spatial and temporal variability of these quantities. However, we are most interested in the radiative forcing since the preindustrial era. Because few relevant measurements are available from that era, relationships from recent variability have been assumed to be applicable to the preindustrial to present-day change. Our analysis of Aerosol Comparisons between Observations and Models (AeroCom) model simulations suggests that estimates of relationships from recent variability are poor constraints on relationships from anthropogenic change for some terms, with even the sign of some relationships differing in many regions. Proxies connecting recent spatial/temporal variability to anthropogenic change, or sustained measurements in regions where emissions have changed, are needed to constrain estimates of anthropogenic aerosol impacts on cloud radiative forcing.


What controls the vertical distribution of aerosol? Relationships between process sensitivity in HadGEM3–UKCA and inter-model variation from AeroCom Phase II

Atmospheric Chemistry and Physics 16 (2016) 2221-2241

Z Kipling, P Stier, CE Johnson, GW Mann, N Bellouin, SE Bauer, T Bergman, M Chin, T Diehl, SJ Ghan, T Iversen, A Kirkevåg, H Kokkola, X Liu, G Luo, T van Noije, KJ Pringle, K von Salzen, M Schulz, Ø Seland, RB Skeie, T Takemura, K Tsigaridis, K Zhang


Effect of aerosol subgrid variability on aerosol optical depth and cloud condensation nuclei: implications for global aerosol modelling

ATMOSPHERIC CHEMISTRY AND PHYSICS 16 (2016) 13619-13639

N Weigum, N Schutgens, P Stier

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