Extensive aerosol optical properties, particle size distributions, and Aerodyne quadrupole aerosol mass spectrometer measurements collected during TRAMP/TexAQS 2006 were examined in light of collocated meteorological and chemical measurements. Much of the evident variability in the observed aerosol-related air quality is due to changing synoptic meteorological situations that direct emissions from various sources to the TRAMP site near the center of the Houston-Galveston-Brazoria (HGB) metropolitan area. In this study, five distinct long-term periods have been identified. During each of these periods, observed aerosol properties have implications that are of interest to environmental quality management agencies. During three of the periods, long range transport (LRT), both intra-continental and intercontinental, appears to have played an important role in producing the observed aerosol. During late August 2006, southerly winds brought super-micron Saharan dust and sea salt to the HGB area, adding mass to fine particulate matter (PM2.5) measurements, but apparently not affecting secondary particle growth or gas-phase air pollution. A second type of LRT was associated with northerly winds in early September 2006 and with increased ozone and sub-micron particulate matter in the HGB area. Later in the study, LRT of emissions from wildfires appeared to increase the abundance of absorbing aerosols (and carbon monoxide and other chemical tracers) in the HGB area. However, the greatest impacts on Houston PM2.5 air quality are caused by periods with low-wind-speed sea breeze circulation or winds that directly transport pollutants from major industrial areas, i.e., the Houston Ship Channel, into the city center.

A radiative transfer model and photochemical box model are used to examine the effects of clouds and aerosols on actinic flux and photolysis rates, and the impacts of changes in photolysis rates on ozone production and destruction rates in a polluted urban environment like Houston, Texas. During the TexAQS-II Radical and Aerosol Measurement Project the combined cloud and aerosol effects reduced j(NO2) photolysis frequencies by nominally 17%, while aerosols reduced j(NO2) by 3% on six clear sky days. Reductions in actinic flux due to attenuation by clouds and aerosols correspond to reduced net ozone formation rates with a nearly one-to-one relationship. The overall reduction in the net ozone production rate due to reductions in photolysis rates by clouds and aerosols was approximately 8 ppbv h(-1). (C) 2009 Elsevier Ltd. All rights reserved,

Despite emission reductions, Houston continues to be designated as a nonattainment area for ozone (O3) by the Environmental Protection Agency. Upper‐level synoptic maps and information about the vertical structure of the lower troposphere obtained by in situ measurements were analyzed to characterize ozone exceedances in which peak 8‐h average concentration exceeded 85 ppb during the Texas Air Quality Study‐II in August–September 2006. Cluster analysis of meteorological conditions showed that the highest background surface O3 concentrations occurred under northerly or easterly flow regimes at 850 hPa, coinciding with the advection of dry continental air. Exceedance days in September 2006 occurred almost exclusively in postfrontal environments. These frontal passages are associated with shifts in wind direction and may lead to increases in background O3 from 30 ppbv (marine) to 60–70 ppbv (continental) throughout the lower troposphere. Several factors are identified to be important for 8‐h average ozone peaks in Houston under well‐developed land‐sea‐bay breeze conditions, including (1) the presence of easterly winds advecting industrial emissions from the Ship Channel, and (2) the presence of persistent large‐scale northerly flows aloft advecting elevated continental background ozone levels that are eventually entrained into lower layers through the growth of the convective planetary boundary layer.

During TEXAQS-II ozonesondes were launched on 20 days during August 2006 and 11 days during September 2006 from the University of Houston (UH) campus to retrieve information about the vertical distribution of ozone. The UH campus site (29.7421 N and 95.3395 W, 11 m a.s.l.) was chosen due to its central location approximately 5 km to the southeast of downtown Houston and thus it is the most representative site to characterize the structure and dynamics of the urban boundary layer in the Houston area. Launches occurred at approximately 1300 CDT. On intensive operation periods, two launches were performed; at 700 and approximately 1300 CDT. Ozonesonde data coverage was 87.5%, representing 35 successes out of 40 launches. For the balloon-borne ozone measurements, aqueous solution Model 2Z electrochemical concentration cell (ECC) ozonesondes manufactured by EN-SCI Corporation of Boulder, Colorado, were used.

Grass fires, although not as intense as forest fires, present a major threat to life and property during periods of drought in the Great Plains of the United States. Recently, major wildland grass fires in Texas burned nearly 1.6 million acres and destroyed over 730 homes and 1320 other buildings. The fires resulted in the death of 19 people, an estimated loss of 10,000 head of livestock, and more than $628 million in damage, making the 2005/06 fire season the worst on record for the state of Texas. As an aid to fire management, various models have been developed to describe fire behavior. However, these models strongly emphasize fuels and fail to adequately consider the role of convective dynamics within the atmosphere and its interaction with the fire due to the lack of observational data. To fill this gap, an intensive field measurement campaign called FireFlux was conducted during February 2006 near Houston, Texas. The campaign employed a variety of instrument platforms to collect turbulence data at multiple levels within and immediately downwind of a 155 acre tall-grass prairie burn unit. This paper presents some first-time observations of atmospheric turbulent structures /fluxes associated with intense grass fires and provides a basis to further our understanding of the dynamics of grass fires and their interactions with the atmosphere.

An air quality forecasting system for Eastern Texas has been developed utilizing the customized MM5/SMOKE/CMAQ modeling system. We performed 2-day air quality forecasting simulations for the 12km Eastern Texas regional domain, and the 4 km Houston-Galveston area (HGA) domain. Dynamic boundary conditions were provided by the 36km resolution conterminous US (CONUS) domain CMAQ simulations. Initial meteorological conditions were provided by the daily Eta forecast results. A set of complex operational scripts was used to allow automatic operation of the data download, sequencing processors, performing simulations and graphical analyses, building database archives, and presenting on the web. The public access web-based user interface has been developed to link the air quality forecasting results with other GIS databases including population and health effects databases. Three different streams of air quality forecasting with slightly different meteorological model options were performed during the summer and fall 2005. The ozone forecasting results were evaluated daily with meteorological and air quality measurements from the surface continuous air monitoring sites in HGA.

G rass fires, although not as intense as forest fires, present a major threat to life and property during periods of drought in the Great Plains of the United States. Recently, major wildland grass fires in Texas burned nearly 1.6 million acres and destroyed over 730 homes and 1320 other buildings. The fires resulted in the death of 19 people, an estimated loss of 10,000 head of livestock, and more than $628 million in damage, making the 2005/06 fire season the worst on record for the state of Texas (Weaver 2006). Research scientists and engineers have developed various models such as BehavePlus (Andrews et al. 2005), FARSITE (Finney 1998), and Prometheus (Tymstra et al. 2007) to describe fire behavior as an aid to fire management. Most of these models emphasize fuels and basic weather conditions reflected by Fire spreading across a prairie during

Since the summer of 2004, over 200 ozonesondes have been launched from the campuses of Rice University or the University of Houston (29.7 N, 95.3 W), each about 3 miles from downtown Houston. These sounding launches have been sponsored by NASA, the Shell Center for Sustainability of Rice University, and the Texas Commissions for Environmental Quality as part of a large effort to understand Houstonʼs ozone problem. Data from these soundings have provided valuable insight into the seasonal and diurnal variations of the vertical ozone distribution and their relationship to changes in atmospheric conditions. In this presentation, we show annual and seasonal variability in the ozone profile, evidence for the impact of meteorological factors on the ozone profile, and comparisons of the ozonesonde data with TES and OMI retrievals. December 10 14, 2007 AGU 2007 Fall Meeting