Chemical transformations of pollutants during winter: First results from the WINTER 2015 aircraft campaign

Lyatt Jaeglé, Viral Shah, Jessica Haskins, Joel Thornton, Felipe Lopez-Hilfiker, Ben Lee

University of Washington, Department of Atmospheric SciencesSteve Brown (NOAA), Jose Jimenez (U Colorado), Jack Dibb (U New

Hampshire), Ron Cohen (UC Berkeley), Rodney Weber (Georgia Tech), Andy Weinheimer, Teresa Campos, Eric Apel, Sam Hall (NCAR), Glenn

Wolfe (NASA GSFC)

What: Atmospheric chemistry aircraft campaign How: NSF/NCAR C-130 aircraft When: Feb 1-Mar 15 2015Where: NE US (based at NASA Langley)

Examine wintertime emissions (dormant biosphere!) and export

Characterize chemical transformations in winter when photochemistry is slow: nocturnal, multiphase processes

Understand factors controlling secondary aerosol formation

Why WINTER?

Fraction of NOx removal by N2O5

Summer

Winter

50-70%

30%

NSF/NCAR C-130 aircraft flight tracks

day SZA

Feb-Mar 2015: 13 flights

DC-Philly-NYC pollution: Feb 3, 2015

NOx: Brown (NOAA); HNO3: Thornton (UW) pNO3: Jimenez (CU)

New York City

NOx: 970 hPappbv

D.C.

Philadelphia

Obs:2.9 ppbvModel: 2.2 ppbv

Good agreement for NOxModel pNO3 too high by x2 overestimate in HNO3 production?[Zhang et al., 2012; Heald et al, 2012]

HNO3(g)+pNO3

model

obs

UTC time

UTC time

D.C.Philly

NYC

[modelobs

NOx

Infer γ(N2O5) from observations

𝜏(NO3)-

1,

s-1

k[N

O2][

O3]/

[NO

3]

Keq[NO2] ･ SA ･ c/4

slope

Approach ofBrown et al. (2006)

Model: γ(N2O5)=0.02Obs:γ(N2O5)=0.01

(0.02-0.004)

Modelγ(N2O5) too high by a factor of 2-4!NO2, NO3, N2O5: Brown (NOAA); N2O5 (Lopez-Hilfiker)

Nighttime NOx chemistry: Feb 3, 2015 Nighttime chemistry:NO2 + O3 NO3

NO3 + NO2 ⇄ N2O5

N2O5 + aerosol 2HNO3

γ(N2O5) = f(RH, aerosol type, T) Mcintyre & Evans (2010), Zhang et al. (2012)

model

N2O5

NO3

NO2

Obs

Obs

Nighttime NOx chemistry: Feb 3, 2015 Nighttime production of ClNO2:N2O5 + Cl- ClNO2 + NO3

-

In GEOS-Chem:Use γ’(N2O5) =0.03 on sea salt and γ’(N2O5) =0.006 for other aerosolsClNO2 + hν NO2 + Cl

ClNO2

Obs

Efficient production of ClNO2 offshore!

UTC time

WINTER ClNO2 observations

MCM box model

ClNO2: Lopez-Hilfiker & Thornton (UW)

pptv

ClNO2+hv

O(1D)+H2O

model

Vertical profiles: 9 WINTER flights

O3: Campos (NCAR), NOx & NOy: Brown (NOAA), Aerosol: Jimenez (CU)

Model NOx too low by 50%lower γ(N2O5) longer lifetime?emissions?planetary boundary layer too shallow?

Model OK for O3, but a bit low: low NOx?

Modeled pNO3 too high by x2

OrganicNitrate

AmmoniumSulfate

Obs

Model

NOx

obsmodel

O3

pNO3 too high

2015 was a COLD winter in the NE US…Feb-Mar mean temperatures over

NE US

Tem

pera

ture

(°C

)

NOAA NCDC1901-2000 Mean: -2.7oC

2012

2015

…how was nitrate affected?

pNO3-/[pNO3

- +HNO3(g)]

Feb-Mar 2012

Feb-Mar 2015

pNO3 fraction, %

2015: 70-90% as pNO3-

2012: 30-60% as pNO3

-

950 hPa

950 hPa

pNO3 fraction, %

WINTER Observations<1km

Next steps/questions Why is N2O5 aerosol uptake so slow? What is the yield of ClNO2? How does it affect the

NOx lifetime, O3 and VOCs? Can use the WINTER observations to constrain

emissions of pollutants and their export? How to the aircraft observations relate to surface

observations?

A hazy sunrise over the Appalachians

PBL Height during winter: comparison to CALIPSO

Planetary boundary layer heights derived from CALIPSO aerosol backscatter profiles

February-March 2006-2012 PBLH

CALIPSO2006-2013

GEOS-FP2013-2014

Ratio: CALIPSO/GEOS-FP

Over land: GEOS-FP PBLH too low

by 30%