Trace-gas Measurements at the Galveston and Manvel Croix Sites

Measurements of Trace Gases at the Manvel Croix and Galveston Sites during DISCOVER-AQPaul Kelley1,2, Winston Luke2, Xinrong Ren1,21Dept of Atmos. & Oceanic Sci., Univ. of Maryland2NOAA Air Resources Laboratory

Objectives:Measurements of trace gases at the two sites in support of DISCOVER-AQ Comparison of surface measurements with aircraft profiling observationsOzone production efficiency using the correlation between O3 and NOz

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Surface Measurements at Manvel-Croix and GalvestonNOAA: NO2 based on Cavity Ring DownTCEQ: O3, NO/NOx and MetLocated to S of downtown Houston and SW of the Houston Ship ChannelNOAA: 3-channel NO/NO2/NOY, O3 and SO2.TCEQ: O3, NO/NOx and MetLocated to SSE of Texas City and SW of downtown Galveston and the Port of Galveston2Diurnal [NO2] Variation at Manvel CroixMax. [NO2] of 11 ppbv at 7:00-8:00 CST. Min. [NO2] of 1-2 ppbv in the afternoonSlightly increasing in early evening: lower boundary heights?

Ranged from close to zero to 29 ppbv (10-sec data)Typical day-to-day variations with peak during morning rush hour.3Elevated [NO2] at Manvel CroixHigh [NO2] in the winds from NE & N. Elevated [NO2] in almost all directions: suggesting nearby local emissions.

NO2 at Manvel Croix and Comparison with the P-3

P3 CL: chemiluminescence P3 LIF: laser induced fluorescence Limit P-3 data at Manvel Croix: (1) below 600 m (2000 ft)(2) within +/-0.02 Lat/Long of the siteGeneral good agreement

5P-3 [NO2] vs. surface [NO2] at Manvel CroixGood agreement in generalMore scattered at lower [NO2] later in the day

Fractionof dayFractionof dayP-3 [O3] vs. surface [O3] at Manvel CroixVery good agreement with little dependence on time of day.Fractionof day

P-3 [O3] vs. surface [O3] at GalvestonGood agreement with little dependence on time of day.Fractionof day

Limit P-3 data at Galveston : (1) below 300 m (1000 ft)(2) within +/-0.02 Long/Lat of the site

P-3 [NO2] vs. surface [NO2] at GalvestonReasonable agreement in general.More scattered than Manvel Croix: more horizontal/vertical gradients due to the location of the site.Fractionof day

Wind dependence of [NOY] and [SO2] at GalvestonHighest [NOY] and [SO2] were observed in the winds from NNE , where downtown Galveston and the Port of Galveston are located. Galveston: [NOZ] (= [NOY] [NOX])

Peak NOz (~1.2 ppb) in the afternoon photochemical formation. Nighttime NOz levels: relatively constant (~0.7-0.8 ppbv).

Galveston: Ox (=O3+NO2) vs. NOzData collected from 10am to 6pm (CST) at the surfaceSpecific for mean transport times from the emission source regions to Galveston Assuming minimal depositional loss of NOY species such as HNO3.

Similar slopes (14-16) using the P-3 data during the spirals at Galveston and Smith Point. During daytime: 10am-6pm (CST)About 16 ppb O3 is created when 1 ppb NOx converted to NOy.During DAQ-Baltimore/Washington 2011, this number is ~5-6.

12High NO2 levels at Manvel Croix were influenced by plumes from downtown Houston and the Houston Ship Channel.

Trace gases at Galveston: relatively low levels, but influenced by pollution plumes.

Comparisons with the P-3 data: good agreement at Manvel Croix and more scattered at Galveston.

Estimated ozone production efficiency of ~16 ppb O3/ppb NOx conversion at Galveston: a factor of 2-3 larger than that during DISCOVER-AQ 2011 in the Baltimore-Washington area.Summary AQRP & TCEQ for support

Jim Thomas, Vince Torresm, and Raj Nadkarni for logistic support

Dave Sullivan and Maria Stanzione for project management support

The P-3 science team for use of the aircraft data

Mark Estes for providing the TCEQ data

Russ Dickerson for loaning instrument supported by AQAST

Acknowledgements