Science Focus Area: Brookhaven and Argonne National Laboratories

Principal Investigator(s):
Michael Jensen, Brookhaven National Laboratory

Co-Investigator(s):
V. Rao Kotamarthi, Argonne
Robert McGraw, Brookhaven
Chongai Kuang, Brookhaven
Art Sedlacek, Brookhaven
Andrew Vogelmann, Brookhaven
Yan Feng, Argonne
Virendra Ghate, Argonne
Scott Giangrande, Brookhaven
Larry Kleinman, Brookhaven
Pavlos Kollias, Brookhaven
Ernie Lewis, Brookhaven
Yangang Liu, Brookhaven

The research within this Science Focus Area (SFA) supports the mission of the DOE Atmospheric System Research Program to advance process-level understanding of the key interactions among aerosols, clouds, precipitation, radiation, dynamics, and thermodynamics, with the ultimate goal of reducing the uncertainty in global and regional climate simulations and projects. The long-term objectives of this SFA are articulated through the following decadal goals:

  • Determine the effects of cloud-scale dynamical and microphysical processes on cloud structure relevant to improved process representations and narrowing the range of climate model sensitivities.
  • Reduce uncertainties in radiative forcing due to aerosol indirect effects by determining the impact of aerosol on cloud microphysics and macrophysical structure under representative cloud and synoptic regimes.
  • Characterize, using field and laboratory measurements, the microphysical and optical properties and the processes that control these properties for carbonaceous absorbing aerosols (CAA) most important to climate forcing and the hydrologic cycle, and to improve representation of these processes and properties in models to better quantify CAA direct, indirect and semi-direct effects.
  • Quantify understanding of the aerosol number and cloud condensation nuclei (CCN) concentration budgets and their controlling processes in regions where the impact of aerosol is most significant (e.g., marine environment with extensive low cloud coverage and polar regions), as well as its representation and validation in climate models.
  • Develop high-resolution modeling capabilities to interface with these process-level studies to improve the representation of aerosols and clouds in climate and earth system models, and work closely with the climate modeling community to bridge the gap between these high-resolution and larger-scale models.

To make significant progress towards these crosscutting objectives, the science plan builds upon a new collaboration between Brookhaven National Laboratory and Argonne National Laboratory to pursue focused research efforts within three main thrusts:

  • Evolution of carbonaceous absorbing aerosol properties.
  • Formation, growth and removal of atmospheric aerosols.
  • cloud properties and processes.

Evolution of Carbonaceous Absorbing Aerosol Properties

  • Accurate estimates and model-based representation of radiative forcing by particles containing black carbon (BC), brown carbon (BrC), or both requires more than one class of BrC, each with a different absorption spectrum.
  • Evolution of light absorption by BrC leads to a reduction of the radiative forcing by BrC particles and BrC-coated BC particles that is not accounted for in global models.
  • Improvements in the representation of the light-absorption properties of BrC (Hypothesis 1) and the atmospheric processes that modify them (Hypothesis 2) will better constrain the direct and semi-direct radiative forcings by carbonaceous absorbing aerosols.

Formation, Growth and Removal of Atmospheric Aerosols

  • Atmospheric nucleation occurring aloft is a significant source of newly formed particles measured at the surface.
  • Atmospheric nucleation is often dominated/controlled by the activation/heterogeneous nucleation of neutral clusters, which are always present.
  • The variations of the aerosols entrained from free troposphere and their subsequent growth contribute substantially to the seasonal variation in marine boundary layer CCN population.
  • The removal of the CCN by droplet coalescence and wet deposition is strongly coupled to cloud regime and mesoscale structure, and the observed spatial variation of CCN concentration is to a large degree driven by the removal.
  • Cloud Properties and Processes

    • Turbulent mixing and giant CCN contribute significantly to the variability of microphysical process rates especially at low liquid water path.
    • Dispersion effects, entrainment-mixing processes, regime dependence and process couplings are key factors buffering aerosol-cloud interactions (ACI).
    • Cold pool structure is a response to rather than a driver of evolution in mesoscale structure within drizzling stratocumulus.
    • For a given thermodynamic profile, the first-order variance in liquid water fraction in high latitude mixed-phase clouds is explained by turbulent vertical mixing with a secondary influence from variations in aerosol loading.
    • Composite heating rate profiles can sufficiently characterize deep convective mesoscale organization at global climate model scales.
    • For deep convection, relationships between core size and updraft strength are strongly correlated to the wind shear, followed by near-storm thermodynamic conditions.
    • To address these hypotheses, the SFA team’s approach is multi-scale—from molecular to microphysical and eddy to cloud-resolving scales. The acquisition of process-level understanding over multiple scales is, by its nature, integrative and requires a spectrum of research components. The objectives outlined in this science plan will be met by the research team through approaches using Atmospheric Radiation Measurement fixed site and field campaign measurements, state-of-the-art retrieval techniques, laboratory experiments, theoretical development, and high-resolution modeling studies.

      Read more about this SFA in this ASR feature story.