Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

All day
 
 
Before 01
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
 
Atmospheric Chemistry Program Seminar

Atmospheric Chemistry Program Seminar

Revisiting dry deposition of trace gases and particles in the atmosphere

Delphine K. Farmer
Associate Professor, Department of Chemistry, Colorado State University

"Dry deposition is a key process that removes trace gases and particles from the atmosphere, and thus one factor that controls the atmospheric lifetime of pollutants and short-lived climate forcers. In fact, dry deposition is the single largest component of uncertainty in our understanding of aerosol effects on climate. Despite its importance, dry deposition of trace gases and particles is poorly constrained by observations due to the instrumental challenge in measuring surface-atmosphere exchange. Instruments must be adequately fast, sensitive and selective to measure low concentrations on the rapid (<1 s) timescale of turbulence. We have developed several measurement techniques that use the eddy covariance approach to flux measurements over terrestrial surfaces incorporating both spectroscopy and mass spectrometry. This talk will be divided into two parts – the first considering the mechanisms that control forest-atmosphere exchange of acidic organic molecules, and the second revisiting our understanding of size-resolved particle deposition in the atmosphere. We contrast these observations with previous measurements in the literature, and with commonly used resistance models, highlighting several model-measurement discrepancies. To further investigate the mechanisms of particle deposition, we use black carbon deposition as an inert tracer for particle wet and dry deposition. We show that wet deposition dominates in an agricultural environment in Oklahoma, and provide observational constraints on black carbon lifetime in this region. Our suite of observations inform a revised model parameterization, which we incorporate in a global chemical transport model to investigate how dry deposition can impact particle loading and the radiative balance of the atmosphere. Together, these new measurements highlight the importance of observational constraints in developing, validating, and revising models of fundamental chemical and physical processes in the atmosphere – and in reducing uncertainties in our understanding of climate."

date

Monday, February 10, 2020
12:00pm

location

Ekeley S274

Event Type

Seminar

resources

Amenities

Lunch provided

contact

Anne.Handschy@colorado.edu
2020-02-10