Tropospheric ozone sources and wave activity over Mexico City and Houston during MILAGRO/Intercontinental Transport Experiment (INTEX-B) Ozonesonde Network Study, 2006 (IONS-06)

Abstract

Abstract. During the INTEX-B (Intercontinental Chemical Transport Experiment)/MILAGRO (Megacities Initiative: Local and Global Research Observations) experiments in March 2006 and the associated IONS-06 (INTEX Ozonesonde Network Study; http://croc.gsfc.nasa.gov/intexb/ions06.html), regular ozonesonde launches were made over 15 North American sites. The soundings were strategically positioned to study inter-regional flows and meteorological interactions with a mixture of tropospheric O3 sources: local pollution; O3 associated with convection and lightning; stratosphere-troposphere exchange. The variability of tropospheric O3 over the Mexico City Basin (MCB; 19 N, 99 W) and Houston (30 N, 95 W) is reported here. MCB and Houston profiles displayed a double tropopause in most soundings and a subtropical tropopause layer with frequent wave disturbances, identified through O3 laminae as gravity-wave induced. Ozonesondes launched over both cities in August and September~2006 (IONS-06, Phase 3) displayed a thicker tropospheric column O3 (~7 DU or 15–20%) than in March 2006; nearly all of the increase was in the free troposphere. In spring and summer, O3 laminar structure manifested mixed influences from the stratosphere, convective redistribution of O3 and precursors, and O3 from lightning NO. Stratospheric O3 origins were present in 39% (MCB) and 60% (Houston) of the summer sondes. Comparison of summer 2006 O3 structure with summer 2004 sondes (IONS-04) over Houston showed 7% less tropospheric O3 in 2006. This may reflect a sampling contrast, August to mid-September 2006 instead of July–mid August 2004.

Impacts of background ozone production on Houston and Dallas, Texas, air quality during the Second Texas Air Quality Study field mission

“…The 50th percentile (red and yellow bars) and 90th percentile (lines) within 50‐mbar pressure intervals are also shown. The mean P3 profile is consistent with the mean of August 2006 ozonesonde profiles from midday daily launches over Houston [ Thompson et al , 2008].…”

“…The analyzed ozone is systematically high by 10 ppbv (∼15%) throughout the column relative to the P3. Note that the mean ozone measured by the P3 is similar to that for the Houston ozonesondes [ Thompson et al , 2008, Figure 5d]. This is in contrast to the underestimate in TOC relative to OMI‐RAQMS strat .…”

“…Observation System Experiment (OSE) studies were conducted to further quantify the impact of TES and TES+OMI assimilation on the RAQMS ozone analysis. As part of IONS‐06 [ Thompson et al , 2008] 376 North American ozonesondes were launched during August 2006, 19 of them at the University of Houston (29.7°N, 95.4°W). A series from 31 July to 11 September 2006, was launched from the Research Vessel Ronald H. Brown operating in the Houston‐Galveston area.…”

Investigation of Vertical Profiles of Meteorological Parameters and Ozone Concentration in the Mexico City Metropolitan Area

“…During our observation campaigns, tropopause was found around 15 km ASL. The growing maximum of O 3 concentration around 13 km ASL from 13 March 2012 can be attributed to stratospheric influence as described by Danielsen (1968) and Thompson et al (2008).…”

“…Especially, the significance of frequent and deep soundings should be emphasized; the twicedaily ozondesonde observations thro ugh and beyond the mixing layer enabled estimation of the amount of photochemically produced ozone, and the fourtimesdaily radiosonde observations help ed iden tify the causes for the behaviors where the ∆Q O 3 T max relation was exceptional. In the past studies, similar analysis could not be conducted because the vertical soundings were either frequent but shallow (tethered balloons; Velasco et al, 2008), or deep but infrequent (onceorlessdaily ozonesonde; Thompson et al, 2008).…”