Summer wind flow regimes over the Sacramento Valley

This study utilized conditional sampling to identify three frequent wind re gimes in the lower Sacramento Valley. The major flow features of the mean d iurnal wind patterns in the southern Sacramento Valley and surrounding area s were analyzed for each wind regime. Afternoon wind directions at a pivota l observing site (Davis, CA) in the south-central part of the valley were u sed to classify the regimes as south wind (marine air intrusion), north win d (no marine air intrusion), and transitional wind days. In the summer of 1 991, these occurred 72%, 14%, and 14% of the days, respectively. Daily data from 21 surface observing stations were segregated by wind regime, then av eraged for quarters of the day to produce wind roses grouped by regime and time of day. These data were then plotted on a base map. The most frequent direction in each of these wind roses was used to construct streamlines for the area by quarter of the day for each regime. These analyses provide a c limatology of the diurnal variation of the average wind flow for each of th ese frequent flow regimes, providing a wind climatology with greater spatia l and temporal resolution than those in extant publications. These analyses are especially useful for evaluating transport patterns of air pollutants or contaminants.