2011 Progress Report: Particle-Resolved Simulations for Quantifying Black Carbon Climate Impact and Model UncertaintyEPA 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: Hunt, Sherri
Project Period: June 1, 2011 through May 31, 2014 (Extended to May 31, 2015)
Project Period Covered by this Report: June 1, 2011 through May 31,2012
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
- Calculate key quantities for modeling black carbon effects in global and regional climate simulations (including the aging timescale, optical properties, and cloud condensation nuclei [CCN] number)
- Quantify the uncertainty in these quantities in climate predictions resulting from inadequate representation of black carbon aerosol mixing state in existing models; and
- Provide a testbed for the evaluation of proposed new approximate aerosol modeling algorithms.
In the first year of this project, we targeted the following milestones:
- We designed and built a "scenario library" of approximately 300 PartMC-MOSAIC 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.
- 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. The aging time-scale is heavily dependent on the chosen supersaturation threshold. Decreasing this threshold from 0.6% to 0.1% increases the aging time-scale by a factor of 20 (median). The nitrate-dominated simulations, which have the highest gas-to-particle conversion, lead to the lowest aging timescales, with day-time averages on the order of 1 hour for the 0.6% supersaturation threshold. This value depends in turn on temperature and relative humidity as they govern nitrate formation. Daytime aging time-scales are about a factor of 5 smaller than the corresponding nighttime aging time-scales when the 0.6% supersaturation threshold is used. This day-night difference decreases for smaller supersaturation thresholds.
- We performed the first comparison of PartMC-MOSAIC results with observations using data from a ship plume study in the English Channel. Detailed process analysis of the simulations revealed that the most important processes shaping the particle distribution were coagulation and dilution with background air. Coagulation significantly altered the mixing state of the particles leading to a continuum of internal mixtures of sulfate, black carbon and organic carbon, while ash particles remained largely externally mixed.
- We developed a sectional model version of PartMC-MOSAIC to enable error quantification due to internal mixture assumptions.
The objectives for Year 2 of this project include:
- Development of scenarios that are consistent with conditions of megacities in India.
- Validating PartMC with data from other field campaigns.
- Continued development of sectional model version to enable error quantification: we currently are extending the sectional code to also include advection by chemistry.