Uncertainty in global CCN concentrations from uncertain aerosol nucleation and primary emission rates

Abstract. The indirect effect of aerosols on climate is highly uncertain and limits our ability to assess anthropogenic climate change. The foundation of this uncertainty is uncertainty in the number of cloud condensation nuclei (CCN), which itself stems from uncertainty in aerosol nucleation, primary emission and growth rates. In this paper, we use a global general circulation model with aerosol microphysics to assess how the uncertainties in aerosol nucleation, emission and growth rates affect our prediction of CCN(0.2%) concentrations. Using two nucleation rate parameterizations that differ in globally averaged nucleation rate by 106, the tropospheric average CCN(0.2%) concentrations vary by 17% and the boundary layer average vary by 12%. This sensitivity of tropospheric average CCN(0.2%) to the nucleation parameterizations increases to 33% and 20% when the total primary emissions are reduced by a factor of 3 and the SOA condensation rates are increased by a factor of 3.5, respectively. These results show that it is necessary to understand better global nucleation rates when determining CCN concentrations. When primary emissions rates are varied by a factor of 3 while using the slower nucleation rate parameterization, tropospheric average CCN(0.2%) concentrations also vary by 17%, but boundary layer average vary by 40%. Using the faster nucleation rate parameterization, these changes drop to 3% and 22%, respectively. These results show the importance of reducing uncertainties in primary emissions, which appear from these results to be somewhat more important for CCN than the much larger uncertainties in nucleation. These results also show that uncertainties in nucleation and primary emissions are more important when sufficient condensable material is available to grow them to CCN sizes. The percent change in CCN(0.2%) concentration between pre-industrial times and present day does not depend greatly on the nucleation rate parameterization used for our base case scenarios; however, because other factors, such as primary emissions and SOA, are uncertain in both time periods, this may be a coincidence.

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Uncertainty in global CCN concentrations from uncertain aerosol nucleation and primary emission rates

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-1339-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 1339-1356 ◽

Cited By ~ 255

Author(s):

J. R. Pierce ◽

P. J. Adams

Keyword(s):

Boundary Layer ◽

Nucleation Rate ◽

Growth Rates ◽

General Circulation ◽

Cloud Condensation Nuclei ◽

Circulation Model ◽

Base Case ◽

Emission Rates ◽

Binary Nucleation ◽

Primary Emissions

Abstract. The indirect effect of aerosols on climate is highly uncertain and limits our ability to assess anthropogenic climate change. The foundation of this uncertainty is uncertainty in the number of cloud condensation nuclei (CCN), which itself stems from uncertainty in aerosol nucleation, primary emission and growth rates. In this paper, we use a global general circulation model with aerosol microphysics to assess how the uncertainties in aerosol nucleation, emission and growth rates affect our prediction of CCN(0.2%) concentrations. Using several nucleation rate parameterizations that span six orders of magnitude of globally averaged nucleation rates, the tropospheric average CCN(0.2%) concentrations vary by 17% and the boundary layer average vary by 12%. This sensitivity of tropospheric average CCN(0.2%) to the nucleation parameterizations increases to 33% and 20% when the total primary emissions are reduced by a factor of 3 and the SOA condensation rates are increased by a factor of 3.5, respectively. These results show that it is necessary to better understand global nucleation rates when determining CCN concentrations. When primary emissions rates are varied by a factor of 3 while using a binary nucleation parameterization, tropospheric average CCN(0.2%) concentrations also vary by 17%, but boundary layer average vary by 40%. Using the fastest nucleation rate parameterization, these changes drop to 3% and 22%, respectively. These results show the importance of reducing uncertainties in primary emissions, which appear from these results to be somewhat more important for CCN than the much larger uncertainties in nucleation. These results also show that uncertainties in nucleation and primary emissions are more important when sufficient condensable material is available to grow them to CCN sizes. The percent change in CCN(0.2%) concentration between pre-industrial times and present day does not depend greatly on the nucleation rate parameterization used for our base case scenarios; however, because other factors, such as primary emissions and SOA, are uncertain in both time periods, this may be a coincidence.

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Evaluation of the global aerosol microphysical ModelE2-TOMAS model against satellite and ground-based observations

Geoscientific Model Development ◽

10.5194/gmd-8-631-2015 ◽

2015 ◽

Vol 8 (3) ◽

pp. 631-667 ◽

Cited By ~ 21

Author(s):

Y. H. Lee ◽

P. J. Adams ◽

D. T. Shindell

Keyword(s):

General Circulation ◽

Cloud Condensation Nuclei ◽

Circulation Model ◽

Convective Transport ◽

Emission Rates ◽

Anthropogenic Aerosol ◽

Aerosol Model ◽

Cloud Processing ◽

Aerosol Mass ◽

The Pacific

Abstract. The TwO-Moment Aerosol Sectional (TOMAS) microphysics model has been integrated into the state-of-the-art general circulation model, GISS ModelE2. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the ModelE2-TOMAS model is compared to the default aerosol model in ModelE2, which is a one-moment aerosol (OMA) model (i.e. no aerosol microphysics). Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement (mostly within a factor of 2) with observations of sulfur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as ModelE2-OMA) cannot capture the observed vertical distribution of sulfur dioxide over the Pacific Ocean, possibly due to overly strong convective transport and overpredicted precipitation. The ModelE2-TOMAS model simulates observed aerosol number concentrations and cloud condensation nuclei concentrations roughly within a factor of 2. Anthropogenic aerosol burdens in ModelE2-OMA differ from ModelE2-TOMAS by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. We observed larger differences for naturally emitted aerosols such as sea salt and mineral dust, as those emission rates are quite different due to different upper size cutoff assumptions.

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Antarctic boundary layer parametrization in a general circulation model: 1-D simulations facing summer observations at Dome C

Journal of Geophysical Research Atmospheres ◽

10.1002/2017jd026802 ◽

2017 ◽

Vol 122 (13) ◽

pp. 6818-6843 ◽

Cited By ~ 11

Author(s):

Etienne Vignon ◽

Frédéric Hourdin ◽

Christophe Genthon ◽

Hubert Gallée ◽

Eric Bazile ◽

...

Keyword(s):

Boundary Layer ◽

General Circulation Model ◽

General Circulation ◽

Circulation Model ◽

Antarctic Boundary Layer

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Effects of the planetary waves on the MLT airglow

Annales Geophysicae ◽

10.5194/angeo-35-1023-2017 ◽

2017 ◽

Vol 35 (5) ◽

pp. 1023-1032 ◽

Cited By ~ 4

Author(s):

Fabio Egito ◽

Hisao Takahashi ◽

Yasunobu Miyoshi

Keyword(s):

General Circulation ◽

Atomic Oxygen ◽

Lower Thermosphere ◽

Lower Boundary ◽

Circulation Model ◽

Vertical Transport ◽

Transport Processes ◽

Planetary Waves ◽

Emission Rates ◽

Middle Latitudes

Abstract. The planetary-wave-induced airglow variability in the mesosphere and lower thermosphere (MLT) is investigated using simulations with the general circulation model (GCM) of Kyushu University. The model capabilities enable us to simulate the MLT OI557.7 nm, O2b(0–1), and OH(6–2) emissions. The simulations were performed for the lower-boundary meteorological conditions of 2005. The spectral analysis reveals that at middle latitudes, oscillations of the emission rates with the period of 2–20 days appear throughout the year. The 2-day oscillations are prominent in the summer and the 5-, 10-, and 16-day oscillations dominate from the autumn to spring equinoxes. The maximal amplitude of the variations induced by the planetary waves was 34 % in OI557.7 nm, 17 % in O2b(0–1), and 8 % in OH(6–2). The results were compared to those observed in the middle latitudes. The GCM simulations also enabled us to investigate vertical transport processes and their effects on the emission layers. The vertical transport of atomic oxygen exhibits similar periodic variations to those observed in the emission layers induced by the planetary waves. The results also show that the vertical advection of atomic oxygen due to the wave motion is an important factor in the signatures of the planetary waves in the emission rates.

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Nonlinear Climate and Hydrological Responses to Aerosol Effects

Journal of Climate ◽

10.1175/2008jcli2362.1 ◽

2009 ◽

Vol 22 (6) ◽

pp. 1329-1339 ◽

Cited By ~ 110

Author(s):

Yi Ming ◽

V. Ramaswamy

Keyword(s):

Surface Temperature ◽

Northern Hemisphere ◽

Indirect Effects ◽

General Circulation ◽

Cloud Condensation Nuclei ◽

Circulation Model ◽

Geophysical Fluid Dynamics Laboratory ◽

High Latitudes ◽

Hydrological Responses ◽

Aerosol Effects

Abstract The equilibrium temperature and hydrological responses to the total aerosol effects (i.e., direct, semidirect, and indirect effects) are studied using a modified version of the Geophysical Fluid Dynamics Laboratory atmosphere general circulation model (AM2.1) coupled to a mixed layer ocean model. The treatment of aerosol–liquid cloud interactions and associated indirect effects is based upon a prognostic scheme of cloud droplet number concentration, with an explicit representation of cloud condensation nuclei activation involving sulfate, organic carbon, and sea salt aerosols. Increasing aerosols from preindustrial (1860) to present-day (1990) levels leads to a decrease of 1.9 K in the global annual mean surface temperature. The cooling is relatively strong over the Northern Hemisphere midlatitude land owing to the high aerosol burden there, while being amplified at high latitudes. When being subject to aerosols and radiatively active gases (i.e., well-mixed greenhouse gases and ozone) simultaneously, the model climate behaves nonlinearly; the simulated increase in surface temperature (0.55 K) is considerably less than the arithmetic sum of separate aerosol and gas effects (0.86 K). The thermal responses are accompanied by the nonlinear changes in cloud fields, which are amplified owing to the surface albedo feedback at high latitudes. The two effects completely offset each other in the Northern Hemisphere, while gas effect is dominant in the Southern Hemisphere. Both factors are crucial in shaping the regional responses. Interhemispheric asymmetry in aerosol-induced cooling yields a southward shift of the intertropical convergence zone, thus giving rise to a significant reduction in precipitation north of the equator, and an increase to the south. The simulations show that the change of precipitation in response to the simultaneous increases in aerosols and gases not only largely follows the same pattern as that for aerosols alone, but that it is also substantially strengthened in terms of magnitude south of 10°N. This is quite different from the damping expected from adding up individual responses, and further indicates the nonlinearity in the model’s hydrological response.

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ModelE2-TOMAS development and evaluation using aerosol optical depths, mass and number concentrations

Geoscientific Model Development Discussions ◽

10.5194/gmdd-7-5831-2014 ◽

2014 ◽

Vol 7 (5) ◽

pp. 5831-5918 ◽

Cited By ~ 2

Author(s):

Y. H. Lee ◽

P. J. Adams ◽

D. T. Shindell

Keyword(s):

Organic Matter ◽

General Circulation ◽

Mineral Dust ◽

Cloud Condensation Nuclei ◽

Circulation Model ◽

Convective Transport ◽

Sea Salt ◽

Computationally Efficient ◽

Anthropogenic Aerosol ◽

Aerosol Model

Abstract. The TwO-Moment Aerosol Sectional microphysics model (TOMAS) has been integrated into the state-of-the-art general circulation model, GISS ModelE2. TOMAS has the flexibility to select a size resolution as well as the lower size cutoff. A computationally efficient version of TOMAS is used here, which has 15 size bins covering 3 nm to 10 μm aerosol dry diameter. For each bin, it simulates the total aerosol number concentration and mass concentrations of sulphate, pure elementary carbon (hydrophobic), mixed elemental carbon (hydrophilic), hydrophobic organic matter, hydrophilic organic matter, sea salt, mineral dust, ammonium, and aerosol-associated water. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the TOMAS model is compared to the default aerosol model in ModelE2, which is a bulk aerosol model. Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement with observations of sulphur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as the bulk aerosol model) cannot capture the observed vertical distribution of sulphur dioxide over the Pacific Ocean possibly due to overly strong convective transport. The TOMAS model successfully captures observed aerosol number concentrations and cloud condensation nuclei concentrations. Anthropogenic aerosol burdens in the bulk aerosol model running in the same host model as TOMAS (ModelE2) differ by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. Larger differences are found for naturally emitted aerosols such as sea salt and mineral dust. With TOMAS, ModelE2 has three different aerosol models (the bulk aerosol model and modal-based aerosol microphysics model, MATRIX) and allows exploration of the uncertainties associated with aerosol modelling within the same host model, NASA GISS ModelE2.

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Evaluation of Southern Ocean cloud in the HadGEM3 general circulation model and MERRA-2 reanalysis using ship-based observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-6607-2020 ◽

2020 ◽

Vol 20 (11) ◽

pp. 6607-6630 ◽

Cited By ~ 2

Author(s):

Peter Kuma ◽

Adrian J. McDonald ◽

Olaf Morgenstern ◽

Simon P. Alexander ◽

John J. Cassano ◽

...

Keyword(s):

Boundary Layer ◽

Southern Ocean ◽

General Circulation ◽

Cloud Cover ◽

Atmospheric Stability ◽

Austral Summer ◽

Circulation Model ◽

Radiation Budget ◽

Cloud Albedo ◽

Low Cloud

Abstract. Southern Ocean (SO) shortwave (SW) radiation biases are a common problem in contemporary general circulation models (GCMs), with most models exhibiting a tendency to absorb too much incoming SW radiation. These biases have been attributed to deficiencies in the representation of clouds during the austral summer months, either due to cloud cover or cloud albedo being too low. The problem has been the focus of many studies, most of which utilised satellite datasets for model evaluation. We use multi-year ship-based observations and the CERES spaceborne radiation budget measurements to contrast cloud representation and SW radiation in the atmospheric component Global Atmosphere (GA) version 7.1 of the HadGEM3 GCM and the MERRA-2 reanalysis. We find that the prevailing bias is negative in GA7.1 and positive in MERRA-2. GA7.1 performs better than MERRA-2 in terms of absolute SW bias. Significant errors of up to 21 W m−2 (GA7.1) and 39 W m−2 (MERRA-2) are present in both models in the austral summer. Using ship-based ceilometer observations, we find low cloud below 2 km to be predominant in the Ross Sea and the Indian Ocean sectors of the SO. Utilising a novel surface lidar simulator developed for this study, derived from an existing Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) – active remote sensing simulator (ACTSIM) spaceborne lidar simulator, we find that GA7.1 and MERRA-2 both underestimate low cloud and fog occurrence relative to the ship observations on average by 4 %–9 % (GA7.1) and 18 % (MERRA-2). Based on radiosonde observations, we also find the low cloud to be strongly linked to boundary layer atmospheric stability and the sea surface temperature. GA7.1 and MERRA-2 do not represent the observed relationship between boundary layer stability and clouds well. We find that MERRA-2 has a much greater proportion of cloud liquid water in the SO in austral summer than GA7.1, a likely key contributor to the difference in the SW radiation bias. Our results suggest that subgrid-scale processes (cloud and boundary layer parameterisations) are responsible for the bias and that in GA7.1 a major part of the SW radiation bias can be explained by cloud cover underestimation, relative to underestimation of cloud albedo.

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Numerical simulation of tropospheric injection of biomass burning products by pyro-thermal plumes

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-3463-2010 ◽

2010 ◽

Vol 10 (8) ◽

pp. 3463-3478 ◽

Cited By ~ 34

Author(s):

C. Rio ◽

F. Hourdin ◽

A. Chédin

Keyword(s):

Boundary Layer ◽

Biomass Burning ◽

General Circulation ◽

Circulation Model ◽

Thermal Plume ◽

Near Surface ◽

Fire Emissions ◽

Boundary Layer Height ◽

Convective Structures ◽

Environmental Air

Abstract. The thermal plume model, a mass-flux scheme originally developed to represent the vertical transport by convective structures within the boundary layer, is adapted to the representation of plumes generated by fires, with the aim of estimating the height at which fire emissions are actually injected in the atmosphere. The parameterization, which takes into account the excess of near surface temperature induced by fires and the mixing between convective plumes and environmental air, is first evaluated on two well-documented fires. Simulations over Southern Africa performed with the general circulation model LMDZ over one month show that the CO2 can be injected far above the boundary layer height, leading to a daily excess of CO2 in the mid-troposphere of an order of 2 ppmv. These results agree with satellite retrievals of a diurnal cycle of CO2 in the free troposphere over regions affected by biomass burning in the Tropics.

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