Diurnal patterns of blowing dust on the Llano Estacado

Hourly dust data was collected in Lubbock, Texas, from January 1, 2003, to January 1, 2008. Diurnal patterns of dust concentration were computed by averaging hourly values associated with a given time of day for all days within the 5-yr sampling period. Results suggest that the overall diurnal pattern is characterized by relatively high dust concentrations during the day and relatively low values at night and in the early morning. Diurnal patterns of blowing dust are influenced by daily variations of key climatic factors. Generally, one finds relatively strong winds during the day and lighter winds at night. The morning increase in wind speed is associated with the rising sun, which produces thermal instability and enhances the mixing of high momentum winds from the upper levels of the atmosphere to the surface layer. Solar radiation can also reduce the critical threshold by drying the soil surface. Diurnal patterns of blowing dust were also computed separately for each of the four seasons. The most conspicuous change of the diurnal pattern occurred in the summer where the difference between peak afternoon values and early morning values was considerably less than that of other seasons.