Advancing the Understanding of Cloud Microphysical Processes and Aerosol Indirect Effects in High-Latitude Mixed-Phase Clouds by Linking ARM Measurements with Climate Model Simulations

Advancing the Understanding of Cloud Microphysical Processes and Aerosol

aerosols

Small particles or droplets, such as wildfire smoke, volcanic gases, or salty sea spray, that float in the air. They are emitted by both natural events and human activities.

Source: NASA Global Climate Change Source

Indirect Effects in High-Latitude Mixed-Phase Clouds by Linking ARM Measurements with Climate Model Simulations

Minghui Diao, San Jose State University (Principal Investigator)

Xiaohong Liu, Texas A&M University (Co-Investigator)

The key objectives of this proposal are to advance our understanding of cloud microphysical characteristics and aerosol indirect effects on mixed-phase clouds in the high latitudes. To improve the representation of ice and mixed-phase clouds in global climate models (GCMs), we propose an integrated observation and modeling study of cloud macro- and microphysical properties, including spatial heterogeneities, mass partitioning between ice crystals and supercooled liquid water, effects of ice nucleating particles

ice nucleating particles

Tiny specks of material suspended in the air that act as starting points for the formation of ice crystals in clouds.

Source: Pacific Northwest National Laboratory Source

(INPs), and efficiency of secondary ice production (SIP), etc.

Specifically, we will take four main approaches in this proposed work: (1) examining macro- and microphysical properties of ice and mixed-phase clouds based on in-situ and ground-based observations from multiple field campaigns funded by the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program, including the Mixed-Phase Arctic Cloud Experiment (M-PACE), Indirect and Semi-Direct Aerosol Campaign (ISDAC), Ice Nucleating Particle Sources at Oliktok Point (INPOP), ARM West Antarctic Radiation Experiment (AWARE), Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS), and Macquarie Island Cloud and Radiation Experiment (MICRE); (2) evaluating DOE Energy Exascale Earth System Model (E3SM)

Energy Exascale Earth System Model (E3SM)

The Energy Exascale Earth System Model (E3SM) project includes Earth System Models, simulations, and predictions to investigate energy-relevant science using code optimized for DOE's advanced supercomputers.

Source: NVCL Web Page Source

simulations based on observations, particularly for ice and mixed-phase cloud microphysical properties; (3) examining the impacts of INPs on ice and mixed-phase clouds. Specifically, hemispheric comparisons will be conducted between northern and southern high latitudes using observations over the Arctic, the Southern Ocean and the Antarctica. In addition, aerosol indirect effects from distinct sources of dust particles will be examined; and (4) investigating the impacts of SIP. Ultimately, these tasks will help to improve cloud microphysics and aerosol-cloud interaction

aerosol-cloud interaction

The interaction of airborne particles (aerosols) with clouds. Scientists study how aerosols affect clouds and how these interactions can impact the Earth's climate.

Source: DOE Source

parameterizations in the E3SM model.

The resulting analysis will provide an improved physical basis for refining the current cloud parameterizations in the ice and mixed-phase cloud regime in E3SM. We will run the E3SM model in the weather forecast mode through the DOE Cloud-Associated Parameterizations Testbed (CAPT) and in the single-column mode. In particular, we will develop a method in order to compare high-resolution aircraft observations with coarse-resolution climate model simulations. Impacts of spatial and temporal scales will be investigated in the model-observation comparison. The statistical probability density functions (PDFs) of modeled cloud microphysical properties will be examined in relation to thermodynamic, dynamical and aerosol conditions.

We will utilize a dust source-tagging capability in E3SM to explicitly track dust from various sources. This will provide insights into the relative importance of local dust source versus long-range transported dust from low-latitude sources to INPs in the Arctic. We will also examine the relative importance of dust versus marine organic aerosols contributed to the INPs over the Southern Ocean. The indirect effects of distinct sources of INPs on mixed-phase clouds at high latitudes will be quantified with E3SM constrained by observations of INPs and cloud microphysical properties.

Effects of SIP on mixed-phase cloud properties with respect to primary ice nucleation will be examined with E3SM, in comparison with observational analyses of ice crystal and INP number concentrations and associated thermodynamic and dynamical conditions. Different SIP mechanisms (e.g., rime splintering, ice-ice collision fragmentation, and droplet shattering during freezing) will be compared for their impacts on mixed-phase cloud properties using E3SM.