scholarly journals Earth System Model Aerosol-Cloud Diagnostics Package (ESMAC Diags) Version 1: Assessing E3SM Aerosol Predictions Using Aircraft, Ship, and Surface Measurements

2021 ◽  
Author(s):  
Shuaiqi Tang ◽  
Jerome D. Fast ◽  
Kai Zhang ◽  
Joseph C. Hardin ◽  
Adam C. Varble ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
Number Concentration ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Aerosol Cloud ◽  
Surface Measurements ◽  
Aerosol Number Concentration ◽  
Aerosol Properties

Abstract. An Earth System Model (ESM) aerosol-cloud diagnostics package is developed to facilitate the routine evaluation of aerosols, clouds and aerosol-cloud interactions simulated by the Department of Energy’s (DOE) Energy Exascale Earth System Model (E3SM). The first version focuses on comparing simulated aerosol properties with aircraft, ship, and surface measurements, most of them are measured in-situ. The diagnostics currently covers six field campaigns in four geographical regions: Eastern North Atlantic (ENA), Central U.S. (CUS), Northeastern Pacific (NEP) and Southern Ocean (SO). These regions produce frequent liquid or mixed-phase clouds with extensive measurements available from the Atmospheric Radiation Measurement (ARM) program and other agencies. Various types of diagnostics and metrics are performed for aerosol number, size distribution, chemical composition, CCN concentration and various meteorological quantities to assess how well E3SM represents observed aerosol properties across spatial scales. Overall, E3SM qualitatively reproduces the observed aerosol number concentration, size distribution and chemical composition reasonably well, but underestimates Aitken mode and overestimates accumulation mode aerosols over the CUS region, and underestimates aerosol number concentration over the SO region. The current version of E3SM struggles to reproduce new particle formation events frequently observed over both the CUS and ENA regions, indicating missing processes in current parameterizations. The diagnostics package is coded and organized in a way that can be easily extended to other field campaign datasets and adapted to higher-resolution model simulations. Future releases will include comprehensive cloud and aerosol-cloud interaction diagnostics.

scholarly journals Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: comparison to observations and climate impacts

2020 ◽  
Author(s):  
Sara M. Blichner ◽  
Moa K. Sporre ◽  
Risto Makkonen ◽  
Terje K. Berntsen
Keyword(s):  
Size Distribution ◽  
Large Scale ◽  
Particle Formation ◽  
Early Growth ◽  
Number Concentration ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
New Particle Formation

Abstract. Aerosol-cloud interactions contribute with a large portion of the spread in estimates of climate forcing, climate sensitivity and future projections. An important part of this uncertainty is how much new particle formation (NPF) contributes to cloud condensation nuclei (CCN), and furthermore, how this changes with changes in anthropogenic emissions. Incorporating NPF and early growth in Earth System Models (ESMs) is, however, challenging both due to uncertain parameters (e.g. participating vapours), structural challenges (numerical description of growth from ∼1 to ∼100 nm), and due to large scale of ESM grid compared to NPF scale.A common approach in ESMs is to represent the particle size distribution by a certain number of log-normal modes. Sectional schemes on the other hand, where the size distribution is represented by bins, are considered closer to first principles because they do not make an a priori assumption about the size distribution. In order to improve the representation of early growth, we have implemented a sectional scheme for the smallest particles (5–39.6 nm diameter) in the Norwegian Earth System Model (NorESM), feeding particles into the original aerosol scheme. This is, to our knowledge, the first time such an approach has been tried. We find that including the sectional scheme for early growth improves the aerosol number concentration in the model when comparing against observations, particularly in the 50–100 nm diameter range. Furthermore, we find that the model with the sectional scheme produces much less particles than the original scheme in polluted regions, while it produces more in remote regions and the free troposphere, indicating a potential impact on the estimated aerosol forcing. Finally, we analyse the effect on cloud-aerosol interactions and find that the effect of changes in NPF efficiency on clouds is highly heterogeneous in space. While in remote regions, more efficient NPF leads to higher cloud droplet number concentration (CDNC), in polluted regions the opposite is in fact the case.

scholarly journals Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: comparison to observations and climate impacts

2021 ◽  
Vol 14 (6) ◽  
pp. 3335-3359
Author(s):  
Sara M. Blichner ◽  
Moa K. Sporre ◽  
Risto Makkonen ◽  
Terje K. Berntsen
Keyword(s):  
Size Distribution ◽  
Large Scale ◽  
Particle Formation ◽  
Early Growth ◽  
Number Concentration ◽  
Climate Impacts ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
New Particle Formation

Abstract. Aerosol–cloud interactions contribute to a large portion of the spread in estimates of climate forcing, climate sensitivity and future projections. An important part of this uncertainty is how much new particle formation (NPF) contributes to cloud condensation nuclei (CCN) and, furthermore, how this changes with changes in anthropogenic emissions. Incorporating NPF and early growth in Earth system models (ESMs) is, however, challenging due to uncertain parameters (e.g. participating vapours), structural issues (numerical description of growth from ∼1 to ∼100 nm) and the large scale of an ESM grid compared to the NPF scale. A common approach in ESMs is to represent the particle size distribution by a certain number of log-normal modes. Sectional schemes, on the other hand, in which the size distribution is represented by bins, are considered closer to first principles because they do not make an a priori assumption about the size distribution. In order to improve the representation of early growth, we have implemented a sectional scheme for the smallest particles (5–39.6 nm diameter) in the Norwegian Earth System Model (NorESM), feeding particles into the original aerosol scheme. This is, to our knowledge, the first time such an approach has been tried. We find that including the sectional scheme for early growth improves the aerosol number concentration in the model when comparing against observations, particularly in the 50–100 nm diameter range. Furthermore, we find that the model with the sectional scheme produces much fewer particles than the original scheme in polluted regions, while it produces more in remote regions and the free troposphere, indicating a potential impact on the estimated aerosol forcing. Finally, we analyse the effect on cloud–aerosol interactions and find that the effect of changes in NPF efficiency on clouds is highly heterogeneous in space. While in remote regions, more efficient NPF leads to higher cloud droplet number concentration (CDNC), in polluted regions the opposite is in fact the case.

scholarly journals Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

2010 ◽  
Vol 10 (6) ◽  
pp. 15629-15670
Author(s):  
P. Shrestha ◽  
A. P. Barros ◽  
A. Khlystov
Keyword(s):  
Boundary Layer ◽  
Chemical Composition ◽  
Organic Carbon ◽  
Size Distribution ◽  
Elemental Carbon ◽  
Monsoon Season ◽  
Number Concentration ◽  
Water Soluble ◽  
Aerosol Size Distribution ◽  
Aerosol Number Concentration

Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May–June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevation in the Middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14~340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and water-soluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional period of boundary layer growth and collapse. The increase in number concentration during the peak period was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shallow concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64~68%) of the aerosol concentration followed by ionic species (24~26% mainly SO42- and NH4+). Elemental Carbon (EC) compromised 7~10% of the total composition. A large fraction of OC was found to be water soluble (nearly 27% at both sites).

Modelling choices with regard to aerosol-cloud interactions and their impact on effective climate sensitivity in the NorESM2 model

2021 ◽  
Author(s):  
Sabine Undorf ◽  
Frida Bender
Keyword(s):  
Climate Change ◽  
Climate Sensitivity ◽  
Liquid Water ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Anthropogenic Aerosols ◽  
Aerosol Cloud ◽  
Model Version ◽  
Aerosol Cloud Interactions

<p>Aerosol-cloud interactions (ACIs) continue to be subject to much uncertainty, supporting a large set of parametric and structural variants of a global climate or Earth System Model (ESM), especially regarding its aerosol and cloud microphysics components. This structural model uncertainty is relevant not only for the quantification of the climate response to anthropogenic aerosols: Because aerosol-cloud interactions are at the core of cloud and precipitation formation, they might also affect model-simulated cloud adjustments and feedbacks in response to greenhouse gases, and hence the model’s effective climate sensitivity (ECS). In-situ observations, satellite retrievals, and large-eddy simulations point to discrepancies between the effects of aerosol-cloud interactions in the real world and as modelled in ESMs, with potential implications for the model range also for ECS. </p><p>Here, we explore how different choices in ACI modelling affect the model’s ECS. For this case study the CMIP6-generation Norwegian Earth System Model version 2 (NorESM2) is used, which has a sophisticated aerosol module and in its ‘default’ version contributed to the CMIP6 suite relatively weak positive cloud feedbacks compared to the other models within the 150 years used to calculate the regression-based ECS (EffCS). The climate change feedback and hence ECS of each modified model version compared to that of the default one is estimated by prescribing a uniform rise of 4K in the sea-surface temperature boundary conditions and evaluating the resulting top-of-atmosphere imbalance difference. A similar or better representation of present-day mean climate in general and ACI effects in particular is ensured by comparing a suite of evaluation metrics with their observationally derived pendants and results from the literature.</p><p>The ACI effects and relevant model-observation discrepancies targeted with the model modifications include models’ excessive cloud brightening over stratocumulus regions compared to satellite products, excessive increase in liquid water path associated with increased aerosol amount, and model bias in the climatological fraction between supercooled liquid water and cloud ice in mixed-phase clouds. For each of these, experiments with multiple combinations of modifications in the model code are analysed, exemplifying the numerous different processes and parameters that together determine the model response. The findings complement approaches to explore models’ parameter spaces systematically by informing the choices physically and restricting the modifications not only to parametric changes. The range of models obtained sets the default NorESM2 version, with its ECS being part of the CMIP6 ensemble, into the context of ACI uncertainty, informs on the so far possibly underappreciated relevance of ACIs for climate change beyond anthropogenic aerosols, and suggests alternative parameterisations for future ‘default’ model versions.</p><div>2.11.0.0</div>

scholarly journals Coupling of a sediment diagenesis model (MEDUSA) and an Earth system model (CESM1.2): a contribution toward enhanced marine biogeochemical modelling and long-term climate simulations

2020 ◽  
Vol 13 (2) ◽  
pp. 825-840 ◽  
Author(s):  
Takasumi Kurahashi-Nakamura ◽  
André Paul ◽  
Guy Munhoven ◽  
Ute Merkel ◽  
Michael Schulz
Keyword(s):  
Chemical Composition ◽  
Model Uncertainty ◽  
Bottom Water ◽  
Coupled Model ◽  
Earth System Model ◽  
System Model ◽  
Future Application ◽  
Earth System ◽  
Climate Simulations

Abstract. We developed a coupling scheme for the Community Earth System Model version 1.2 (CESM1.2) and the Model of Early Diagenesis in the Upper Sediment of Adjustable complexity (MEDUSA), and explored the effects of the coupling on solid components in the upper sediment and on bottom seawater chemistry by comparing the coupled model's behaviour with that of the uncoupled CESM having a simplified treatment of sediment processes. CESM is a fully coupled atmosphere–ocean–sea-ice–land model and its ocean component (the Parallel Ocean Program version 2; POP2) includes a biogeochemical component (the Biogeochemical Elemental Cycling model; BEC). MEDUSA was coupled to POP2 in an offline manner so that each of the models ran separately and sequentially with regular exchanges of necessary boundary condition fields. This development was done with the ambitious aim of a future application for long-term (spanning a full glacial cycle; i.e. ∼105 years) climate simulations with a state-of-the-art comprehensive climate model including the carbon cycle, and was motivated by the fact that until now such simulations have been done only with less-complex climate models. We found that the sediment–model coupling already had non-negligible immediate advantages for ocean biogeochemistry in millennial-timescale simulations. First, the MEDUSA-coupled CESM outperformed the uncoupled CESM in reproducing an observation-based global distribution of sediment properties, especially for organic carbon and opal. Thus, the coupled model is expected to act as a better “bridge” between climate dynamics and sedimentary data, which will provide another measure of model performance. Second, in our experiments, the MEDUSA-coupled model and the uncoupled model had a difference of 0.2 ‰ or larger in terms of δ13C of bottom water over large areas, which implied a potentially significant model uncertainty for bottom seawater chemical composition due to a different way of sediment treatment. For example, an ocean model that does not treat sedimentary processes depending on the chemical composition of the ambient water can overestimate the amount of remineralization of organic matter in the upper sediment in an anoxic environment, which would lead to lighter δ13C values in the bottom water. Such a model uncertainty would be a fundamental issue for paleo model–data comparison often relying on data derived from benthic foraminifera.

scholarly journals Evaluation of aerosol number concentrations in NorESM with improved nucleation parameterisation

2013 ◽  
Vol 13 (10) ◽  
pp. 26389-26450
Author(s):  
R. Makkonen ◽  
Ø. Seland ◽  
A. Kirkevåg ◽  
T. Iversen ◽  
J. E. Kristjánsson
Keyword(s):  
Size Distribution ◽  
Correlation Coefficient ◽  
Seasonal Cycle ◽  
High Sensitivity ◽  
Organic Aerosol ◽  
Number Concentration ◽  
System Model ◽  
Vertical Profiles ◽  
Earth System ◽  
Atmospheric Observations

Abstract. The Norwegian Earth System Model (NorESM) is evaluated against atmospheric observations of aerosol number concentrations. The model is extended to include an explicit mechanism for new particle formation, and the secondary organic aerosol (SOA) formation from biogenic precursors is revised. Several model experiments are conducted to study the sensitivity of simulated number concentrations to nucleation, SOA formation, black carbon size distribution and model meteorology. Comparison against 60 measurement sites reveals that the model with improved nucleation and SOA scheme performs well in terms of correlation coefficient R2=0.41 calculated against monthly mean observed aerosol number concentrations with a number concentration bias of −6%. NorESM generally overestimates the amplitude of the seasonal cycle, possibly due to too high sensitivity to biogenic precursors. Simulated vertical profiles are also evaluated against 12 flight campaigns.

scholarly journals Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

2010 ◽  
Vol 10 (23) ◽  
pp. 11605-11621 ◽  
Author(s):  
P. Shrestha ◽  
A. P. Barros ◽  
A. Khlystov
Keyword(s):  
Boundary Layer ◽  
Chemical Composition ◽  
Organic Carbon ◽  
Size Distribution ◽  
Elemental Carbon ◽  
Monsoon Season ◽  
Number Concentration ◽  
Water Soluble ◽  
Aerosol Size Distribution ◽  
Aerosol Number Concentration

Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May–June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevations in the middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14–340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and water-soluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional periods of boundary layer growth and collapse. The increase in number concentration during the peak periods was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shallow concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64–68%) of the aerosol concentration followed by ionic species (24–26%, mainly SO42− and NH4+). Elemental Carbon (EC) compromised 7–10% of the total composition and 27% of OC was found to be water soluble at both sites. The day-to-day variability observed in the time series of aerosol composition could be explained by the synoptic scale haze that extended to the sampling region from the Indian Gangetic Plain (IGP), and rainfall occurrence. In the presence of regional scale haze during dry periods, the mean volume aerosol concentration was found to increase and so did the aerosol mass concentrations.

Estimating the Sensitivity of Radiative Impacts of Shallow, Broken Marine Clouds to Boundary Layer Aerosol Size Distribution Parameter Uncertainties for Evaluation of Satellite Retrieval Requirements

2011 ◽  
Vol 28 (4) ◽  
pp. 530-538 ◽  
Author(s):  
Ann M. Fridlind ◽  
Andrew S. Ackerman
Keyword(s):  
Boundary Layer ◽  
Size Distribution ◽  
Case Studies ◽  
Number Concentration ◽  
Effective Radius ◽  
Aerosol Size Distribution ◽  
Parameter Uncertainties ◽  
Analytic Estimate ◽  
Aerosol Number Concentration ◽  
Aerosol Properties

Abstract A proposed objective of the planned Aerosol–Cloud–Ecosystem (ACE) satellite mission is to provide constraints on climate model representation of aerosol effects on clouds by retrieving profiles of aerosol number concentration, effective variance, and effective radius over the 0.1–1-μm radius range under humidified ambient conditions with 500-m vertical resolution and uncertainties of 100%, 50%, and 10%, respectively. Shallow, broken marine clouds provide an example of conditions where boundary layer aerosol properties would be retrieved in clear-sky gaps. To quantify the degree of constraint that proposed retrievals might provide on cloud radiative forcing (CRF) simulated by climate models under such conditions, dry aerosol size distribution parameters are independently varied here in large-eddy simulations of three well-established modeling case studies. Using the rudimentary available aerosol specifications, it is found that relative changes of total dry aerosol properties in simulations can be used as a proxy for relative changes of ambient aerosol properties targeted by ACE retrievals. The sensitivity of simulated daytime shortwave CRF to the proposed uncertainty in retrieved aerosol number concentration is −15 W m−2 in the overcast limit, roughly a factor of 2 smaller than a simple analytic estimate owing primarily to aerosol-induced reductions in simulated liquid water path across this particular set of case studies. The CRF sensitivity to proposed uncertainties in retrieved aerosol effective variance and effective radius is typically far smaller, with no corresponding analytic estimate. Generalization of the results obtained here using only three case studies would require statistical analysis of relevant meteorological and aerosol observations and quantification of observational and model uncertainties and biases.

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