Simulating isoprene oxidation in GFDL AM3 model

Jingqiu Mao (NOAA GFDL), Larry Horowitz (GFDL), Vaishali Naik (GFDL), Meiyun Lin (GFDL), Arlene Fiore (Columbia U)

Funding from NOAA CPO

Summertime ozone over eastern US is a problem for most models

(Fiore et al., 2009, JGR)

Multimodel mean

Obs from CASTNET surface sites

Northeast US

Southeast US

Multimodel mean

Obs from CASTNET surface sites

Standard AM3

(Naik et al., 2013, JGR, in press)

A new isoprene chemistry for global models

(Mao et al., submitted to JGR)

ISOPO2 + NO is based on Paulot et al. (2009, ACP).ISOPO2 + HO2 is based on Paulot et al. (2009, Science).Isomerization of ISOPO2 is based onPeeters et al. (2009, PCCP) and Crounse et al. (2011, PCCP) .

How fast is the isomerization?

NO

12

34

OH

11.7%

O

MVK

First generation isoprene nitrates

O

MACRH

O

H

HCHO

88%Organic peroxides

OHOO

OO

OH

-hydroxyl peroxy radicaland isomers

-hydroxyl peroxy radicaland isomers

71% 29%

HO2 1,6-H shif t isomerization

4.7%

7.3%

12%26% 40% 66%

HOOO

HPALDs

hvOH100%

100%

C2 and C3 carbonyl compounds

ISOPO2 ISOPO2

Was OH really that high over SE US during ICARTT?

(Ren et al., 2008, JGR)

OH measured by traditional method during ICARTT 2004

(Mao et al., 2012, ACP)

Part of OH signal could be due to interference, probably from Criegee Intermediate!

A new method of measuring OH was deployed in Blodgett Forest

First generation of isoprene nitrates degraded to second generation nitrates!OH

ONO2

ISOPN (1,4)

OHONO2

ISOPN (1,2)

OHONO2

ISOPN (4,3)

ONO2

OH

ISOPN (4,1)

O

OH

ONO2

methylvinylketone nitrate (MVKN)

O

ethanal nitrate(ETHLN)

O

propanone nitrate(PROPNN)

O

methacrolein nitrate(MACRN)

ONO2

OH

OH/O2

OH

ONO2

OHOO

NO

OH

ONO2

OHO

OHONO2

OHOO

NO

OHONO2

OHO

ONO2

OH

OHOO

NO

ONO2

OH

OHO

OHONO2

OHOO

NO

OHONO2

OHO

OH/O2OH/O2OH/O2

O2NO

O2NO Second generation isoprene nitrates (C3-C4)

First generation isoprene nitrates (C5)

C5 alkyl nitrate is short-lived due to oxidation by OH and ozone, with photochemical lifetime of 2-3 hrs.

Consistent with measurements from Thornton’s group, C5<< C4.

NO3

ONO2

OO

NO3

ONO2

O

ONO2

O

OH

O2NO

O

R4N2

Nighttime chemistry

Based on Rollins et al. (2009) and Xie et al. (2012)

Nighttime yield of organic nitrates is 70%>> daytime yield (11.7%)

This chemistry was implemented in GEOS-Chem

Ozone in the boundary layer during ICARTT 2004Observations Model

Obs vs. ModelImproved O3-CO correlations due to:1. Recycling of NOx

from isoprene nitrates

2. HO2 uptake (lower OH and increase NOx lifetime).

(Mao et al., submitted to JGR)

Mean vertical profiles during ICARTT

O3 has no bias in boundary layer and free troposphere.HCHO provides good constraint on isoprene emissions.

ObservationsModel (GEOS-Chem)

(Mao et al., submitted to JGR)

Total organic nitrates excluding peroxyacylnitrates (∑ANs)

Model well reproduced ∑ANs.

∑ ANs is dominated by secondary organic nitrates(C3-C4).

∑ANs vs. HCHO ∑ANs vs. O3

Model well reproduced ∑ANs vs. HCHO and ∑ANs vs. O3 correlations.

These correlations cannot be reproduced by a fast isomerization channel of ISOPO2.

Vertical profiles Speciation of ∑ANs

NOy budget in eastern U.S. boundary layer for July 2004

Species Emission Chemical(P-L)

Dry Deposition

Wet Deposition

Net Export

NOx 386 -337 44 ------ 5PANs   24 13 ------ 11∑ANs           ANs   18 7.4 3.6 7 R4N2   10 0.5 ------- 10HNO3   277 180 110 -3

Export of ∑ANs > Export of PANs

New chemistry

Previous studies without NOx recycling

Current anthro NOx emissions (2004)

Reduce current anthro NOx emissions by 50%

Isoprene↑NOx ↓OH ↓O3 ↓ due to O3+ISOP

Surface ozone response to isoprene emissions

NOx emissions↓

Sensitivity of ozone to isoprene emissions ↓

GFDL AM3 configuration for SENEX• Fully coupled chemistry-climate model

o Parameterizes aerosol activation into liquid cloud dropletso solves both tropospheric and stratospheric chemistry over the full domain

• Nudging wind with GFS meteorological field• High resolution (50 x 50 km) and coarse resolution (200 x 200 km)• MEGAN biogenic emissions• Anthropogenic emissions use RCP 8.5 scenario (0.5 x 0.5 degree)• New isoprene chemistry (Mao et al., submitted to JGR)• New heterogeneous chemistry (Mao et al., 2013a, ACP; 2013b, GRL)

C48 (200 x 200km) C180 (50 x 50km)

Monthly mean ozone for July of 2012

Updated chemistry Standard AM3 Observations

CASTNET sites

Improvement on ozone over SE US

(Naik et al., 2013, JGR, in press)

• Bias is reduced from 12.9 ppbv to 3.3 ppbv.• This should be reexamined by MDA8 ozone. Model tends to

overestimate monthly mean ozone.

Standard AM3 New chemistry in AM3

Sunrise

Entrainment zone

Model shows large amount of VOCs and OVOCs in the residual layer.

Is it possible to do a early morning flight to see the entrainment zone?

Boundary layer structure by Stull (1988).

Does nighttime chemistry affect global nitrogen/ozone budget?

Sunset

HCHO yield at different NOx conditions

Computed in a photochemical box model. Initialized with 1ppb isoprene.O3 (40ppb), CO (100ppb), and NOx are held constant.

Prompt HCHO formation, important for deriving isoprene emission from satellite observations.

Yield of HCHO is lower at lower NOx concentrations, according to the model.

But the model could be wrong!

Next step: merging in-cloud SOA module with new isoprene chemistry

(Ford et al., 2013, ACPD)A new module of in-cloud SOA production developed in AM3 (Liu et al., 2012, JGR)

(Lamsal et al., 2010)

Surface NOx emissions >> other emissions above the surface.

10% leak of surface NOx will double the effect of lightning.

Surface NOx ventilation will be critical for NOx/ozone in free trop

Observed ventilation from LIDAR (aerosol profiles Jul. 3, 2001, Barcelona, Campus Nord, UPC)!