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  • HOx and NO Observations during INTEX-A

    X. Ren J. Mao R. Long R. Lesher W. Brune Department of Meteorology

    Pennsylvania State University

  • HOx and NO measurement techniques

    • OH and HO2 measurements ATHOS — Airborne Tropospheric Hydrogen Oxides

    Sensor – Laser-induced fluorescence (LIF) detection of OH

    – Chemically convert HO2 to OH by HO2+NO followed by the detection of OH with LIF

    • NO measurements TEI 42C NO-NOx analyzer

    – Chemiluminescence – NO single mode – Online NO span and zero checks

  • Data Quality

    • Data coverage: OH (1 min) - 97% HO2 (1 min) - 95% NO (1 min) - 89%

    • Typical uncertainties: HOx ±32% (2σ) NO ±30% (2σ)

    • Detection limits: OH 0.01 pptv HO2 0.1 pptv NO 50 ppt

  • 0

    5

    10

    15 A

    LT P

    (k m

    ) ALT P

    0

    0.2

    0.4

    0.6

    O H

    (p pt

    v) OH obs

    0

    20

    40

    H O

    2 (p

    pt v) HO2 obs

    12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 0

    500

    1000

    N O

    (p pt

    v)

    Hour (UTC)

    NO obs

    HOx and NO observations (July 22, Flight 11)

    HO2 and OH have good precision – sub-minute resolution will be used to examine variability.

  • Observed & PSS NO vertical profiles

    1 10 100 1000 0

    2

    4

    6

    8

    10

    12

    NO (pptv)

    A LT

    P (k

    m )

    NO obs NO obs median NO PSS median

    0 1 2 3 0

    2

    4

    6

    8

    10

    12

    NO obs / NO PSS

    A LT

    P (k

    m )

    The NO values between 2-6 km are around or below the NO detection limit (~50 pptv).

  • 0 20 40 0

    2

    4

    6

    8

    10

    12

    HO2

    A lti

    tu de

    ( km

    ) obs obs mod

    0 1 2 3 HO2 obs/mod

    INTEX INTEX TRACEP PEMTB

    • Median observed-to-modeled OH ~ 0.6 at all altitudes. • Median observed-to-modeled HO2 ~ 0.8 up to 8 km. • Behavior is similar to that in TRACE-P. • Large observed-to-modeled OH in PBL correlates to

    isoprene (from Jim Crawford) as seen in forests.

    0 0.2 0.4 0.6 0

    2

    4

    6

    8

    10

    12

    OH

    A lti

    tu de

    ( km

    )

    obs obs mod

    0 1 2 3 OH obs/mod

    INTEX INTEX TRACEP PEMTB

    (pptv) (pptv)

  • 50 100150 0

    2

    4

    6

    8

    10

    12

    CO (ppbv)

    A lti

    tu de

    ( km

    )

    101 102 103 NOx (pptv)

    50 100 O3 (ppbv)

    0 50 100 150 0

    2

    4

    6

    8

    10

    12

    HO2/OH

    A lti

    tu de

    ( km

    )

    obs obs mod

    0 1 2 3 HO2/OH obs/mod

    INTEX INTEX TRACEP PEMTB

    • NOx in INTEX-A is greater than in TRACE-P & PEM TB; CO and O3 are similar in INTEX-A & TRACE-P.

    • Observed-to-modeled HO2/OH is close to 1 below 7 km, but exceeds 2 above ~9 km.

    • HO2/OH deviations appear to be NOx related.

  • 0.2

    0.4

    0.6

    O H

    obs obs mod

    100 102 0

    1

    2

    3

    O H

    o bs

    /m od

    NOx (pptv)

    INTEX INTEX TRACEP PEMTB

    20

    40

    H O

    2

    obs obs mod

    100 102 0

    1

    2

    3

    H O

    2 ob

    s/ m

    od

    NOx (pptv)

    INTEX INTEX TRACEP PEMTB

    • Observed-to-modeled OH shows little NOx-dependence. • Observed-to-modeled HO2 grows for NOx > few 100 pptv. • INTEX-A and TRACE-P dependences on NOx are similar. • Observed-to-modeled HO2 < 1 for NOx < few 100 pptv &

    > 1 for NOx > few 100 pptv is usually observed by us and a few others.

  • HO2 versus (PHOx)1/2

    0 2000 4000 6000 8000 0

    2

    4

    6

    8

    10

    12

    14

    sqrt [P(HOx)] (sqrt [cm -3 s-1])

    H O

    2 o bs

    (x 10

    8 c m

    -3 )

    • P(HOx) = L(HOx) ∝ [ HO2 ]2, so [ HO2 ] ∝ sqrt {P(HOx)}. • Much HO2 variance can be explained by P(HOx).

  • HOx observed & modeled comparisons

    0.01 0.1 1 10 0.01

    0.1

    1

    10

    OH mod (pptv)

    O H

    o bs

    ( pp

    tv )

    median obs/calc =0.58 r2 = 0.64

    1 10 100 1

    10

    100

    HO2 mod (pptv)

    H O

    2 ob

    s (p

    pt v)

    median obs/calc =0.77 r2 = 0.65

    • Solid line: 1:1; dashed lines: obs. uncertainty ±32%. • HOx comparison similar to that in TRACE-P.

  • Modeled OH production and loss

    105 106 107 108 0

    2

    4

    6

    8

    10

    12

    P(OH) (cm-3)

    A LT

    P (k

    m )

    POH POH median O1D+H2O Peroxides HO2+NO

    104 106 108 0

    2

    4

    6

    8

    10

    12

    L(OH) (cm-3)

    A LT

    P (k

    m )

    LOH LOH median OH+CO OH+NO2 OH+HCHO

    Main P(OH) is O1D+H2O (below 5 km) and HO2+NO (above 5 km). Main L(OH) is OH+CO/VOC.

  • Modeled HO2 production and loss

    105 106 107 108 0

    2

    4

    6

    8

    10

    12

    P(HO2) (cm-3)

    A LT

    P (k

    m )

    104 106 108 0

    2

    4

    6

    8

    10

    12

    L(HO2) (cm-3)

    A LT

    P (k

    m )

    PHO2 PHO2 median OH+CO HCHO+hv OH+HCHO

    LHO2 LHO2 median HO2+NO HO2+O3 HO2+RO2

    Main P(HO2) is OH+CO. Main L(HO2) is HO2-RO2 self-reactions (below 5 km) & HO2+NO (above 5 km).

  • O3 budget

    0.01 0.1 1 10 0

    2

    4

    6

    8

    10

    12

    P(O3) (ppb hr -1)

    A LT

    P (

    km )

    0.01 0.1 1 10 0

    2

    4

    6

    8

    10

    12

    L(O3) (ppb hr -1)

    A LT

    P (k

    m )

    PO3 PO3 median PO2-HO2 PO3-RO2

    LO3 LO3 median LO3-O

    1D LO3-OH LO3-HO2

    -0.5 0 0.5 1 1.5 0

    2

    4

    6

    8

    10

    12

    P(O3), L(O3), P(O3)-L(O3) (ppb hr -1)

    A LT

    P (

    km )

    P(O3) L(O3) P(O3)-L(O3)

    • Main P(O3): HO2+NO.

    • Main L(O3): O1D+H2O (< 5 km) & O3+HO2/OH (> 5 km).

    • Net O3 loss at altitudes between 1 km and 5 km.

  • Science questions we hope to answer • General comparisons between observed and modeled HOx

    – Were previous observed-to-modeled anomalies also observed in INTEX-A? (e.g., NOx-dependence of observed-to-modeled HO2)

    – Can the HOx heterogeneous effects (or lack thereof) be understood?

    • High speed photochemistry – one-to-a-few seconds – What are the effects of scale on calculating P(O3) from HO2 & NO?

    – Is HOx behavior understood in urban, forest-fire, and long-range regionally transported plumes?

    • HOx behavior in the planetary boundary layer – What is the behavior of HOx and P(O3) and vertical distribution in the

    boundary layer? – Is isoprene chemistry in forested regions adequately understood?

    • Collaborations with many others on these & other questions.

    HOx and NO Observations during INTEX-A HO2 versus (PHOx)1/2 HOx observed & modeled comparisons Modeled OH production and loss Modeled HO2 production and loss O3 budget Science questions we hope to answer