2013 Progress Report: Particle-Resolved Simulations for Quantifying Black Carbon Climate Impact and Model Uncertainty

EPA Grant Number: R835042
Title: Particle-Resolved Simulations for Quantifying Black Carbon Climate Impact and Model Uncertainty
Investigators: Riemer, Nicole , West, Matthew
Institution: University of Illinois at Urbana-Champaign
EPA Project Officer: Wilson, Wil
Project Period: June 1, 2011 through May 31, 2014 (Extended to May 31, 2015)
Project Period Covered by this Report: June 1, 2013 through May 31,2014
Project Amount: $449,902
RFA: Black Carbon's Role In Global To Local Scale Climate And Air Quality (2010) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Climate Change , Air

Objective:

The objectives of this project are the following: (1) calculate key quantities for modeling black carbon effects in global and regional climate simulations (including the aging time-scale, optical properties, and cloud condensation nuclei [CCN] number); (2) quantify the uncertainty in these quantities in climate predictions resulting from inadequate representation of black carbon aerosol mixing state in existing models; and (3) provide a testbed for the evaluation of proposed new approximate aerosol modeling algorithms. The objectives of the project have not changed from the original application. To achieve these objectives, we had formulated the following tasks in our proposal: 

Task A:     Construct a suite of eight case studies for the Lagrangian trajectory-model PartMC-MOSAIC, representative of different geographical locations and environments.

Task B:     Validate the PartMC-MOSAIC model in three of these scenarios against experimental data from recent field campaigns.

Task C:     Compute key quantities in each case for black carbon impact, i.e., the aging time-scale, single-scattering albedo, extinction efficiency, asymmetry parameter, and CCN number, including the sensitivity with respect to the time of year, emission pattern, etc.

Task D:     Compute errors in these key quantities due to simplifying assumptions in traditional aerosol models (limited number of size bins, artificial internal mixing, etc.).

Task E:     Formulate numerical parameter estimates and usage recommendations for global and regional climate models. 

Progress Summary:

Recap of status at the end of Year 2 

At the end of Year 2 of the project, we had achieved the following:

  1. Library of idealized urban plume scenarios (Task A): We designed and built a “scenario library” of approximately 300 PartMC scenarios that cover a wide range of conditions regarding meteorology and emission characteristics. This library forms the basis for systematically evaluating key quantities of black carbon impacts and their sensitivity to environmental factors. 
  2. Continued work on the basic algorithmic methods used in PartMC (Task C): 
    1. We developed parallel data processing capabilities to analyze the output of the scenario library with respect to black carbon aging time-scales and determined the range of values for this quantity depending on the environmental conditions. 

    2. We developed a fast binning method for particle sorting that enables more efficient simulation of particle events, especially coagulation (M.D. Michelotti, M.T. Heath, M. West [2013] Binning for efficient stochastic multiscale particle simulations. Multiscale Modeling & Simulation, 11:1071-1096).
  3. Development of scenarios based on and constrained with field campaign data (Task B): 
    1. Work completed for the first data-based scenario: A ship plume study in the English Channel (J. Tian, N. Riemer, M. West, L. Pfaffenberger, H. Schlager, A. Petzold [2014], Modeling the evolution of aerosol particles in a ship plume using PartMC-MOSAIC, Atmos. Chem. Phys., 14:5327-5347).
    2. Work on second data-based scenario started: Black carbon aging during wintertime conditions in the megacity Paris during the MEGAPOLI campaign. 

  4. Development of a quantitative metric of “mixing state”: This work was necessary for the analysis of the scenario library (Task A), the comparison of model results with observations (Task B), and intercomparison of models (Task E). We developed the first quantitative metric for the aerosol population mixing state, defined as the distribution of per-particle chemical species composition. This new metric, the mixing state index χ, is an affine ratio of the average per-particle species diversity and the bulk population species diversity, both of which are based on information-theoretic entropy measures. The mixing state index χ enables the first rigorous definition of the spectrum of mixing states from so-called external mixture to internal mixture, which is significant for aerosol climate impacts, including aerosol optical properties and cloud condensation nuclei activity. We intended this metric to be useful for classifying and comparing aerosol mixing state for different environments (N. Riemer and M. West [2013], Quantifying aerosol mixing state with entropy and diversity measures, Atmos. Chem. Phys., 13:11423-11439).

Research strategy for Year 3 

Based on these achievements our research strategy in Year 3 was as follows:

  1. We applied the newly developed mixing state metrics to quantify aerosol mixing state for the field campaign MEGAPOLI. This work resulted in an ACP paper: R.M. Healy, N. Riemer, J.C. Wenger, M. Murphy, M. West, L. Poulain, A. Wiedensohler, I.P. O’Connor, E. McGillicuddy, J.R. Sodeau, and G.J. Evans [2014], Single particle diversity and mixing state measurements, Atmos. Chem. Phys., 14:6289-6299.  

  2. We continued our work in designing real-world scenarios where black carbon aging takes place in different environments: MEGAPOLI (wintertime conditions in Paris, France) and CARES (summertime conditions in Northern California). 
  3. We formulated a framework for error quantification in CCN properties due to simplified aerosol representation using the mixing state index. 
  4. We made further algorithmic improvements in the underlying PartMC model. First, we developed a new, faster method for deposition sampling based on binned sampling. Second, we are continuing work on acceleration coagulation sampling for rare particles, to speed up the simulations of environments containing low-concentration but high-mass particles (for example, road dust). 

The output and outcomes to date are as follows: 

  • Scenario Library: The scenario library of a wide range of idealized urban plume scenarios is a valuable resource to systematically investigate black carbon aging processes and their impact on climate relevant properties. The usefulness of these data is not only limited to our project, but extends to the community. For example, our collaborators at PNNL use output from the scenario library to benchmark their new multi-dimensional externally mixed sectional aerosol model. 
  • Aging time-scale analyses: Our definition of a black carbon aging time-scale based on CCN activity is a critical step forward as it represents a criterion based on relevant physics. Our method to calculate aging time-scales directly is unique and only possible because we are able to track per-particle composition including both condensation and coagulation as important aging mechanisms. 
  • Theoretical framework for mixing state quantification: The mixing state index χ enables the first rigorous definition of the spectrum of mixing states from so-called external mixture to internal mixture, which is significant for aerosol climate impacts, including aerosol optical properties and cloud condensation nuclei activity. The mixing state index represents a useful metric by which to compare and contrast ambient particle mixing state for different locations globally, for different model scenarios, and to compare and contrast model results and observations. 
  • Development of real-world scenarios: The comparison of PartMC model simulations and ship track data was the first of its kind. We expanded this work by developing scenarios based on data from the MEGAPOLI campaign and based on the CARES campaign. 

Future Activities:

The objectives for the coming year of this project include: 

  • We will complete our suite of real-world scenarios with the scenarios based on the CARES campaign.
  • For the scenarios that we have in place, we will quantify the error in key quantities (aerosol absorption and CCN properties) due to simplifying assumptions regarding aerosol mixing state using the metrics for mixing state as developed as part of this project.
  • We will synthesize the results from the case studies to formulate numerical parameter estimates and usage recommendations for global and regional climate models. 

References:

J Ching, N Riemer, M West. Impacts of black carbon mixing state on black carbon nucleation scavenging: Insights from a particle-resolved model. Journal of Geophysical Research, 117(D23), 2012. 

S Sanyal. Black carbon mixing state in Paris during MEGAPOLI: Connecting particle-resolved observations to particle-resolved modeling. Master’s thesis, University of Illinois at Urbana-Champaign, 2014.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other project views: All 24 publications 9 publications in selected types All 9 journal articles
Type Citation Project Document Sources
Journal Article Healy RM, Riemer N, Wenger JC, Murphy M, West M, Poulain L, Wiedensohler A, O'Connor IP, McGillicuddy E, Sodeau JR, Evans GJ. Single particle diversity and mixing state measurements. Atmospheric Chemistry and Physics 2014;14(12):6289-6299. R835042 (2013)
R835042 (Final)
  • Full-text: ACP-Full Text PDF
    Exit
  • Abstract: ACP-Abstract
    Exit
  • Journal Article Michelotti MD, Heath MT, West M. Binning for efficient stochastic multiscale particle simulations. Multiscale Modeling & Simulation 2013;11(4):1071-1096. R835042 (2012)
    R835042 (2013)
    R835042 (Final)
  • Abstract: SIAM-Abstract
    Exit
  • Journal Article Riemer N, West M. Quantifying aerosol mixing state with entropy and diversity measures. Atmospheric Chemistry and Physics 2013;13(22):11423-11439. R835042 (2012)
    R835042 (2013)
    R835042 (Final)
  • Full-text: ACP-Full Text PDF
    Exit
  • Abstract: ACP-Abstract
    Exit
  • Journal Article Tian J, Riemer N, West M, Pfaffenberger L, Schlager H, Petzold A. Modeling the evolution of aerosol particles in a ship plume using PartMC-MOSAIC. Atmospheric Chemistry and Physics 2014;14(11):5327-5347. R835042 (2012)
    R835042 (2013)
    R835042 (Final)
  • Full-text: ACP-Full Text PDF
    Exit
  • Abstract: ACP-Abstract
    Exit
  • Progress and Final Reports:

    Original Abstract
    2011 Progress Report
    2012 Progress Report
    Final Report