Interactions of Aerosols, Clouds and Precipitation in the Earth System: From molecular scale to global climate simulation
EMSL Project ID
49401
Abstract
This proposal requests cascade resources (0.8M node hours) to produce a more reliable model for climate studies. Staff time is funded with support from other BER projects. Our goals are to (1) improve aerosol treatments in Global Climate Models (GCMs), and (2) perform numerical experiments to understand their impact on the climate system. We also update aerosol radiative properties with better formulations, and then compare with situ field measurements and signatures of the aerosols sampled with an aerosol lidar simulator. We focus on three aerosol types: (1) Sea Spray Aerosols (SSA), (2) Secondary Organic Aerosols (SOA), and (3) nitrate aerosol. Representation of aerosol processes and their interactions with clouds in global climate models is a major source of uncertainty in climate change characterization. Our research aligns with the EMSL's scientific theme: Atmospheric Aerosol Systems making a strong connection from the molecular/nano scale to global climate modeling and EMSL's specific focus on formation mechanisms of organic aerosol, and molecular characteristics of aerosol influencing clouds and climate. Our group has developed a parameterization for SSA enrichment with organic matter, and we are collaborating with EMSL scientists to extend that work through a parallel EMSL experimental proposal led by Prof Rob Walker, U. Montana. We will implement an improved organic adsorption treatment to our SSA composition parameterization, evaluate simulations using observations of the organic mass fraction of marine aerosol, then examine the sensitivity of CCN, cloud droplet number, cloud extent and cloud reflectivity. Lab studies of SOA by Alla Zelenyuk using the EMSL SPLAT II single particle mass spectrometer helped us develop new modeling paradigms for SOA. We are applying our SOA to improve the simulated loadings and lifetimes of organic aerosols and their effects on climate. We will leverage work focused on anthropogenic-biogenic interactions to improve and evaluate our SOA treatment using satellite data in regions strongly affected by biomass burning sources of organic aerosols, and also use field measurements (some taken by EMSL staff) to verify parameterization behavior. Nitrate aerosol will become increasingly important as a climate forcer as anthropogenic sulfur emissions decrease in the future. We are introducing the MOSAIC thermodynamic module into our model to estimate water uptake and droplet nucleation associated with nitrate and an ion-mediated aerosol nucleation mechanism to better simulate the aerosol size distribution. We will evaluate the new source of particle number using condensation nuclei measurements and extend a parallel time-split approach used for sulfuric acid production (vapor formation by gas phase chemistry and condensational loss to SOA) affecting new particle growth to marine organic SSA and MOSAIC nitrate treatments. We will study the impact of these improvements in regions where and periods when nitrate aerosol is important. We also revise radiative properties of carbonaceous aerosols -- a key uncertainty in projections of future climate change -- using a new parameterization of shell-core optics and will evaluate the simulation behavior with a novel satellite simulator strategy. We will use the computer resources for model development, and climate change simulations.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2016-10-01
End Date
2020-03-31
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members