Variations of particulate matter and blowing dust in Lubbock, Texas

Particulate matter (PM) are microscopic solid and liquid particles that are suspended in the atmosphere, separated in to two predominant sizes, PM10 and PM2.5. PM is a hazard to human health and property. In this study, PM2.5 concentrations measured in Lubbock, Texas by the Texas Commission of Environmental Quality (TCEQ) station from 2001 to 2018 were examined for temporal (diurnal, weekly, monthly, seasonal, and annually), meteorological (temperature, relative humidity, wind speed, wind gust, and visibility), and El Niño Southern Oscillation (ENSO) distributions. Majority of the daily average PM2.5 concentrations were below the Environmental Protection Agency (EPA) standard of 35 µg m-3 though there were many high hourly PM2.5 concentrations. No correlation was found between the hourly PM2.5 concentrations and the meteorological parameters. The diurnal distribution showed a bimodal distribution, with morning and evening peaks. April and June had the highest PM2.5 monthly concentrations resulting in spring and summer having the highest seasonal average. Comparing concentrations between ENSO events showed La Niña to have higher PM2.5 concentrations, with maximum concentrations during a weak La Niña. One of the event that contributors to the increasing of atmospheric PM is dust storms. Dust storms are a meteorological phenomenon where high winds loft dust particles into the atmosphere. One of the most important parameters that initiate dust storms is strong wind speeds. These strong winds are caused by synoptic or convective disturbances. This study examines blowing dust days in Lubbock, Texas from 2000 to 2019. To determine a blowing dust day, Meteorological Aerodrome Reports (METARs) from the Lubbock National Weather Service were used. All weather observations associated with dust event (BLDU, DS, DU) were recorded and analyzed to determine diurnal, seasonal, and meteorological patterns. Dust days were separated by meteorological cause (convection vs synoptic) and examined for similarity and differences between the two. Annual dust events did not show any positive or negative trend but did correlate with lower annual precipitation. Comparison of different meteorological parameters between dust days to non-dust days showed that dust days had higher temperatures, higher wind speed, and wind gust, and with lower visibilities and lower relative humidity values. Dust storms days had higher PM2.5 concentrations during La Niña, for both synoptic and convective. Most of the dust storms days were caused by a synoptic disturbance that occurred during the winter months while convective dust storms occurred mostly in June. Synoptic was associated with longer durations compared to the convective events. Convective events were associated with higher temperatures and relative humidity but with lower wind speeds and gusts compared to synoptic dust storm.