Presentation Title

Hygroscopic Growth Measurements of Laboratory Generated Brown Carbon Aerosol: Cloud Formation and Climate Effects

Faculty Mentor

Paula K. Hudson

Start Date

18-11-2017 10:00 AM

End Date

18-11-2017 11:00 AM

Location

BSC-Ursa Minor 128

Session

Poster 1

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

Atmospheric aerosol, small solid and liquid particles suspended in the atmosphere, can affect climate by directly absorbing and/or scattering radiation; or by indirectly acting as cloud condensation nuclei (CCN, a “seed” on which water is adsorbed) to form clouds which then interact with solar radiation. The degree to which a particular type of aerosol affects climate is strongly dependent on its composition as this affects the physicochemical properties of the aerosol; how it interacts with radiation or takes up water. The composition of aerosol particles depends on the generation source of the particles. Given the increase in frequency of forest fires, one aerosol type of particular interest is brown carbon (BrC). BrC is brown in color so it can absorb and re-emit visible radiation resulting in a warming effect on climate. But, BrC can also act as a CCN to form clouds that tend to have a cooling effect. To better understand the cloud formation processes of BrC, the hygroscopic growth of laboratory generated BrC aerosol are studied. Particles are generated by reacting an aldehyde, glyoxal (GX), with a nitrogen containing compound, ammonium sulfate (AS), in varying molar ratios. A tandem differential mobility analyzer (TDMA) is used to measure the water uptake of BrC aerosol by measuring the particle size before and after exposure to increasing relative humidity (RH). Results show that degree of water uptake, and in turn the reflectivity of a formed cloud, is highly dependent on the relative ratio of the reactants GX and AS. For example, particle diameters increase from 11% to 33% at 85% RH as the relative concentration of AS is increased from 2 to 50% suggesting a decrease in cloud reflectivity. Improved quantitative measurements of BrC water uptake can help modelers predict climate changes resulting from increases in wildfire frequency.

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Nov 18th, 10:00 AM Nov 18th, 11:00 AM

Hygroscopic Growth Measurements of Laboratory Generated Brown Carbon Aerosol: Cloud Formation and Climate Effects

BSC-Ursa Minor 128

Atmospheric aerosol, small solid and liquid particles suspended in the atmosphere, can affect climate by directly absorbing and/or scattering radiation; or by indirectly acting as cloud condensation nuclei (CCN, a “seed” on which water is adsorbed) to form clouds which then interact with solar radiation. The degree to which a particular type of aerosol affects climate is strongly dependent on its composition as this affects the physicochemical properties of the aerosol; how it interacts with radiation or takes up water. The composition of aerosol particles depends on the generation source of the particles. Given the increase in frequency of forest fires, one aerosol type of particular interest is brown carbon (BrC). BrC is brown in color so it can absorb and re-emit visible radiation resulting in a warming effect on climate. But, BrC can also act as a CCN to form clouds that tend to have a cooling effect. To better understand the cloud formation processes of BrC, the hygroscopic growth of laboratory generated BrC aerosol are studied. Particles are generated by reacting an aldehyde, glyoxal (GX), with a nitrogen containing compound, ammonium sulfate (AS), in varying molar ratios. A tandem differential mobility analyzer (TDMA) is used to measure the water uptake of BrC aerosol by measuring the particle size before and after exposure to increasing relative humidity (RH). Results show that degree of water uptake, and in turn the reflectivity of a formed cloud, is highly dependent on the relative ratio of the reactants GX and AS. For example, particle diameters increase from 11% to 33% at 85% RH as the relative concentration of AS is increased from 2 to 50% suggesting a decrease in cloud reflectivity. Improved quantitative measurements of BrC water uptake can help modelers predict climate changes resulting from increases in wildfire frequency.