Public Abstract

DE-SC0021001: Characterizing the Small-Scale Dynamical, Ice Microphysical, and Residual Aerosol Properties of Mid-Latitude Cold Clouds: A Pilot Study

Award Status: Inactive

Institution: The Pennsylvania State University, University Park, PA
UEI: NPM2J7MSCF61
DUNS: 003403953

Most Recent Award Date: 07/15/2022
Number of Support Periods: 2
PM: Stehr, Jeffrey

Current Budget Period: 09/15/2021 - 09/14/2023
Current Project Period: 09/15/2020 - 09/14/2023
PI: Harrington, Jerry

Supplement Budget Period: N/A

Public Abstract

Our understanding of cirrus clouds has been advancing rapidly due to improvements in measurements made inside clouds, computer cloud models, and laboratory experimentation. This advancement in knowledge has made it clear that cirrus are complicated systems where the intricate interactions among dynamic air motions, solar and terrestrial radiation, ice crystal growth, and water and air chemistry can substantially influence cirrus structure and evolution. Measurements made inside clouds have shown that cirrus crystals are often complex with shapes that are often cannot be classified, especially at small sizes. Laboratory measurements have revealed that the ice crystal surface is complex, even at small sizes. Recent laboratory and satellite studies show that this surface complexity modifies the radiative properties of cirrus clouds in important ways. Moreover, observations and computer cloud modeling work show that the larger and smaller scale properties of cirrus are sensitive to the interplay between small-scale air motions and the aerosol particles upon which cirrus ice crystals form. Taken together, these studies indicate that accurately accounting for the radiative properties of cirrus clouds requires knowing the air motions and aerosol properties that influence the number concentration and crystal size, along with an understanding of the surface properties of vapor grown ice. Although this prior work has been illuminating, there have been few studies that provide detailed shape and surface complexity measurements for the small ice crystals that often compose cirrus clouds. The goal of this two-year project is to use a new balloon-borne ice crystal sampling system to collect cirrus ice crystals during a three-week long field study at the Southern Great Plains (SGP) site. The balloon-borne system provides measures of the atmospheric temperature, water vapor amount, and ice crystal concentration, along with direct sampling of the ice crystals. The ice crystal samples are stored in liquid nitrogen for transport back to the lab. The crystal shape, surface characteristics and complexity, along with surface aerosol and total aerosol composition will be determined using electron microscopy and mass spectrometry. The aerosol composition will be used to inform cloud computer modeling studies. Prior measurements with the balloon-borne instrument have shown unprecedented detail of crystal surface features, and complex shapes at small crystal sizes. To connect these measurements to the air motions that drive cirrus clouds, radar data collected continuously at the SGP site will be used to estimate of the vertical air motions associated with the cirrus. The balloon-borne ice crystal sampling system has been successfully tested in numerous flights along the U.S. East coast. Data collected with the system will naturally complement current DOE-ARM data products, and the results of these studies will improve our knowledge of cirrus clouds.

Our understanding of cirrus clouds has been advancing rapidly due to improvements in measurements made inside clouds, computer cloud models, and laboratory experimentation. This advancement in knowledge has made it clear that cirrus are complicated systems where the intricate interactions among dynamic air motions, solar and terrestrial radiation, ice crystal growth, and water and air chemistry can substantially influence cirrus structure and evolution. Measurements made inside clouds have shown that cirrus crystals are often complex with shapes that are often cannot be classified, especially at small sizes. Laboratory measurements have revealed that the ice crystal surface is complex, even at small sizes. Recent laboratory and satellite studies show that this surface complexity modifies the radiative properties of cirrus clouds in important ways. Moreover, observations and computer cloud modeling work show that the larger and smaller scale properties of cirrus are sensitive to the interplay between small-scale air motions and the aerosol particles upon which cirrus ice crystals form. Taken together, these studies indicate that accurately accounting for the radiative properties of cirrus clouds requires knowing the air motions and aerosol properties that influence the number concentration and crystal size, along with an understanding of the surface properties of vapor grown ice. Although this prior work has been illuminating, there have been few studies that provide detailed shape and surface complexity measurements for the small ice crystals that often compose cirrus clouds.

The goal of this two-year project is to use a new balloon-borne ice crystal sampling system to collect cirrus ice crystals during a three-week long field study at the Southern Great Plains (SGP) site. The balloon-borne system provides measures of the atmospheric temperature, water vapor amount, and ice crystal concentration, along with direct sampling of the ice crystals. The ice crystal samples are stored in liquid nitrogen for transport back to the lab. The crystal shape, surface characteristics and complexity, along with surface aerosol and total aerosol composition will be determined using electron microscopy and mass spectrometry. The aerosol composition will be used to inform cloud computer modeling studies. Prior measurements with the balloon-borne instrument have shown unprecedented detail of crystal surface features, and complex shapes at small crystal sizes. To connect these measurements to the air motions that drive cirrus clouds, radar data collected continuously at the SGP site will be used to estimate of the vertical air motions associated with the cirrus.

The balloon-borne ice crystal sampling system has been successfully tested in numerous flights along the U.S. East coast. Data collected with the system will naturally complement current DOE-ARM data products, and the results of these studies will improve our knowledge of cirrus clouds.