Publications by Philip Stier

Evaluation of global simulations of aerosol particle number and cloud condensation nuclei, and implications for cloud droplet formation

Atmospheric Chemistry and Physics Discussions European Geosciences Union (2019)

GS Fanourgakis, M Kanakidou, A Nenes, S Bauer, T Bergman, KS Carslaw, A Grini, DS Hamilton, JS Johnson, VA Karydis, A Kirkevag, JK Kodros, U Lohmann, G Luo, R Makkonen, H Matsui, D Neubauer, JR Pierce, J Schmale, PHILIP STIER, K Tsigaridis, T van Noije, H Wang, D WATSON-PARRIS, DM Westervelt, Y Yang, M Yoshioka, N Daskalakis, S Decesari, M Gysel Beer, N Kalivitis, X Liu, NM Mahowald, S Myriokefalitakis, R Schrödner, M Sfakianaki, AP Tsimpidi, M Wu, F Yu

Increased water vapour lifetime due to global warming

Atmospheric Chemistry and Physics Discussions Copernicus GmbH (2019) 1-17

Ø Hodnebrog, G Myhre, BH Samset, K Alterskjær, T Andrews, O Boucher, G Faluvegi, D Fläschner, PM Forster, M Kasoar, A Kirkevåg, J-F Lamarque, D Olivié, TB Richardson, D Shawki, D Shindell, KP Shine, P Stier, T Takemura, A Voulgarakis, D Watson-Parris

<jats:p>&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; The relationship between changes in integrated water vapour (IWV) and precipitation can be characterized by quantifying changes in atmospheric water vapour lifetime. Precipitation isotope ratios correlate with this lifetime, a relationship that helps understand dynamical processes and may lead to improved climate projections. We investigate how water vapour and its lifetime respond to different drivers of climate change, such as greenhouse gases and aerosols. Results from 11 global climate models have been used, based on simulations where CO&lt;sub&gt;2&lt;/sub&gt;, methane, solar irradiance, black carbon (BC), and sulphate have been perturbed separately. A lifetime increase from 8 to 10&amp;amp;thinsp;days is projected between 1986&amp;amp;ndash;2005 and 2081&amp;amp;ndash;2100, under a business-as-usual pathway. By disentangling contributions from individual climate drivers, we present a physical understanding of how global warming slows down the hydrological cycle, due to longer lifetime, but still amplifies the cycle due to stronger precipitation/evaporation fluxes. The feedback response of IWV to surface temperature change differs somewhat between drivers. Fast responses amplify these differences and lead to net changes in IWV per degree surface warming ranging from 6.4&amp;amp;plusmn;0.9&amp;amp;thinsp;%/K for sulphate to 9.8&amp;amp;plusmn;2&amp;amp;thinsp;%/K for BC. While BC is the driver with the strongest increase in IWV per degree surface warming, it is also the only driver with a reduction in precipitation per degree surface warming. Consequently, increases in BC aerosol concentrations yield the strongest slowdown of the hydrological cycle among the climate drivers studied, with a change in water vapour lifetime per degree surface warming of 1.1&amp;amp;plusmn;0.4&amp;amp;thinsp;days/K, compared to less than 0.5&amp;amp;thinsp;days/K for the other climate drivers (CO&lt;sub&gt;2&lt;/sub&gt;, methane, solar irradiance, sulphate).&lt;/p&gt; </jats:p>

Aerosol effects on deep convection: The propagation of aerosol perturbations through convective cloud microphysics

Atmospheric Chemistry and Physics European Geosciences Union (2019)


In-situ constraints on the vertical distribution of global aerosol

Atmospheric Chemistry and Physics Discussions European Geosciences Union (2019)

D WATSON-PARRIS, N Schutgens, C Reddington, K Pringle, D Liu, JA Allan, H Coe, K Carslaw, P STIER

The global aerosol-climate model ECHAM6.3-HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing and climate sensitivity

Geoscientific Model Development Discussions Copernicus GmbH (2019) 1-52

D Neubauer, S Ferrachat, C Siegenthaler-Le Drian, P Stier, DG Partridge, I Tegen, I Bey, T Stanelle, H Kokkola, U Lohmann

<jats:p>&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; The global aerosol-climate model ECHAM6.3-HAM2.3 (E63H23) and the previous model versions ECHAM5.5-HAM2.0 (E55H20) and ECHAM6.1-HAM2.2 (E61H22) are evaluated using global observational datasets for clouds and precipitation. In E63H23 low cloud amount, liquid and ice water path and cloud radiative effects are more realistic than in previous model versions. E63H23 has a more physically based aerosol activation scheme, improvements in the cloud cover scheme, changes in detrainment of convective clouds, changes in the sticking efficiency for accretion of ice crystals by snow, consistent ice crystal shapes throughout the model, changes in mixed phase freezing and an inconsistency in ice crystal number concentration (ICNC) in cirrus clouds was removed. Biases that were identified in E63H23 (and in previous model versions) are a too low cloud amount in stratocumulus regions, deep convective clouds in the Atlantic and Pacific oceans form too close to the continents and there are indications that ICNCs are overestimated.&lt;/p&gt; &lt;p&gt;Since clouds are important for effective radiative forcing due to aerosol-radiation and aerosol-cloud interactions (ERF&lt;sub&gt;ari+aci&lt;/sub&gt;) and equilibrium climate sensitivity (ECS), also differences in ERF&lt;sub&gt;ari+aci&lt;/sub&gt; and ECS between the model versions were analyzed. ERF&lt;sub&gt;ari+aci&lt;/sub&gt; is weaker in E63H23 (&amp;amp;minus;1.0&amp;amp;thinsp;W&amp;amp;thinsp;m&lt;sup&gt;&amp;amp;minus;2&lt;/sup&gt;) than in E61H22 (&amp;amp;minus;1.2&amp;amp;thinsp;W&amp;amp;thinsp;m&lt;sup&gt;&amp;amp;minus;2&lt;/sup&gt;) (or E55H20; &amp;amp;minus;1.1&amp;amp;thinsp;W&amp;amp;thinsp;m&lt;sup&gt;&amp;amp;minus;2&lt;/sup&gt;). This is caused by the weaker shortwave ERF&lt;sub&gt;ari+aci&lt;/sub&gt; (new aerosol activation scheme and sea salt emission parameterization in E63H23, more realistic simulation of cloud water) overcompensating the weaker longwave ERF&lt;sub&gt;ari+aci&lt;/sub&gt; (removal of an inconsistency in ICNC in cirrus clouds in E61H22).&lt;/p&gt; &lt;p&gt;The decrease in ECS in E63H23 (2.5&amp;amp;thinsp;K) compared to E61H22 (2.8&amp;amp;thinsp;K) is due to changes in the entrainment rate for shallow convection (affecting the cloud amount feedback) and a stronger cloud phase feedback.&lt;/p&gt; </jats:p>

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


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


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

Understanding Rapid Adjustments to Diverse Forcing Agents

Geophysical Research Letters American Geophysical Union (2018)

C Smith, R Kramer, G Myhre, P Forster, T Andrews, O Boucher, D Fläschner, Ø Hodnebrog, M Kasoar, V Kharin, A Kirkevag, J-F Lamarque, J Mülmenstädt, D Olivié, T Richardson, B Samset, D Shindell, P STIER, T Takemura, A Voulgarakis, D WATSON-PARRIS

Quantifying the Importance of Rapid Adjustments for Global Precipitation Changes.

Geophysical research letters 45 (2018) 11399-11405

G Myhre, RJ Kramer, CJ Smith, Ø Hodnebrog, P Forster, BJ Soden, BH Samset, CW Stjern, T Andrews, O Boucher, G Faluvegi, D Fläschner, M Kasoar, A Kirkevåg, J-F Lamarque, D Olivié, T Richardson, D Shindell, P Stier, T Takemura, A Voulgarakis, D Watson-Parris

Different climate drivers influence precipitation in different ways. Here we use radiative kernels to understand the influence of rapid adjustment processes on precipitation in climate models. Rapid adjustments are generally triggered by the initial heating or cooling of the atmosphere from an external climate driver. For precipitation changes, rapid adjustments due to changes in temperature, water vapor, and clouds are most important. In this study we have investigated five climate drivers (CO2, CH4, solar irradiance, black carbon, and sulfate aerosols). The fast precipitation responses to a doubling of CO2 and a 10-fold increase in black carbon are found to be similar, despite very different instantaneous changes in the radiative cooling, individual rapid adjustments, and sensible heating. The model diversity in rapid adjustments is smaller for the experiment involving an increase in the solar irradiance compared to the other climate driver perturbations, and this is also seen in the precipitation changes.

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 American Meteorological Society 75 (2018) 425-450

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

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


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


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

The global aerosol-climate model ECHAM6.3-HAM2.3 – Part 1: Aerosol evaluation

Geoscientific Model Development 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 American Institute of Mathematical Sciences (AIMS) 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

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


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

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.

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.