Cluster Analysis of Surface Winds in Houston, Texas, and the Impact of Wind Patterns on Ozone

Abstract

The city of Houston, Texas, is near a complex coastline and numerous petrochemical plants, the combination of which plays a large role in Houston’s air pollution events. It has long been known that the thermally driven afternoon onshore flow (sea breeze or gulf breeze) transports ozone-rich air inland. As a way of quantifying the role of the gulf breeze in Houston’s high-ozone events, cluster analysis of hourly averaged surface winds from a regional network of meteorological sensors was performed for 27 summer days of 2000, with the dates coinciding with the Texas Air Quality Study 2000 (TexAQS 2000). Hourly averaged winds were partitioned into 16 independent clusters, or wind patterns, while simultaneously keeping track of the maximum ozone in the network for each hour. Clusters emerged that represented various wind patterns, including thermally driven flows, stagnant winds, and a thunderstorm outflow. All clusters were used to assess which wind patterns were most likely to be coincident with the maximum ozone of the day. High ozone was most likely to occur with clusters representing the gulf breeze. Clusters occurring before the ozone maximum of the day were analyzed to determine which sequences of wind patterns were most likely to precede high ozone. A transition from offshore flow to onshore flow, with at least 1 h of stagnant winds in between, routinely occurred in the 6 h preceding ozone measurements reaching ≥ 120 parts per billion by volume (ppbv). On nontransition days with high ozone, ozone maxima ≥ 120 ppbv often occurred the hour after a wind direction shift of greater than about 45°.

Seasonal and Diurnal Variations of Total Gaseous Mercury in Urban Houston, TX, USA

“…As a result, a sea breeze is produced when the air flows from the sea to the land at low altitude (<500 m). The low level wind vector then rotates through a clockwise (Northern Hemisphere) cycle under the influence of the Coriolis force [46,47]. As the sea breeze passes through the shoreline, it can bring cleaner marine air to inland areas that can dilute urban/industrial emissions.…”

GC-MS analyses and chemometric processing to discriminate the local and long-distance sources of PAHs associated to atmospheric PM2.5

“…In this study, also two different applications of cluster analysis (CA) were tested to assess the impacts of local circulation and regional-scale transports on PAHs levels. CA has been widely used in atmospheric sciences, e.g., to explore the structure of data and detect the most probable emission sources (Kavouras et al 2001;Contini et al 2010), to highlight group of samples on the basis of their chemical composition (Molinaroli et al 1999;Masiol et al 2010), to manage air quality networking (Pires et al 2008), to classify wind patterns in a region (Kaufmann and Whiteman 1999;Darby 2005), and to group similar back-trajectories and air pathways (Tamamura et al 2007;Ravindra et al 2008b).…”

“…The hourly wind speed (m/s) and direction (degree) from the two meteorological stations were processed, and their scalar components u and v relative to the North-South and West-East axes were calculated (Darby 2005). For the purpose of this study, the hourly values of the components were separately summed to obtain a daily datum, which represents the resultant vector of the air movement.…”

Mass tracking for chemical analysis: the causes of ozone formation in southern Ontario during BAQS-Met 2007

“…Analyses of surface winds, upperlevel synoptic maps, and meteorological conditions have shown that the highest ozone days in that city are associated with the passage of sea-breeze fronts (Darby, 2005;Rappenglück et al, 2008). Cluster analysis of surface winds showed that these events correspond to the situation wherein the transition from offshore to onshore flow is separated by a period of stagnation greater than or equal to one hour, up to six hours before the ozone event (Darby, 2005).…”

“…Analyses of surface winds, upperlevel synoptic maps, and meteorological conditions have shown that the highest ozone days in that city are associated with the passage of sea-breeze fronts (Darby, 2005;Rappenglück et al, 2008). Cluster analysis of surface winds showed that these events correspond to the situation wherein the transition from offshore to onshore flow is separated by a period of stagnation greater than or equal to one hour, up to six hours before the ozone event (Darby, 2005). The timing of the arrival of the sea-breeze front is the key factor in predicting high-pollution events in Houston, and sea breezes in opposition to the synoptic flow lead to the highest pollution, due to recirculation of processed air (Banta et al, 2005).…”