A climatological study of the nocturnal planetary boundary layer

Abstract

Seventy-five nights of fast-response wind and temperature data taken from a 300 m tower near Augusta, GA, were analyzed to determine the time-height structure of the nocturnal planetary boundary layer. The nights were selected from all four seasons over a wide range of synoptic conditions. Statistical summaries of Pasquill-Gifford stability, boundary-layer depth, nocturnal jet height, directional shear, gravity wave occurrence, and azimuthal meandering were obtained. The diversity of nocturnal conditions for the 75 cases resulted in histograms with broad peaks and slowly-varying distributions.To reduce the overall variance, we grouped the nights into two classes: steady nights and unsteady nights. Nights classified as "steady" maintained relatively uniform wind conditions. The data base was large enough to permit a further breakdown of the steady nights into three subclasses based on the height and strength of the wind maximum. "Unsteady" nights were more disturbed, showing timedependent features in the wind field and were also divided into three subclasses, depending on the predominant features observed: microfrontal passage, trend, or variable conditions. Although the subclasses were based mainly on wind structure, they correlated well with other NPBL properties, such as mixed-layer depth and inversion strength. Thus, the classification procedure tended to group together nights with similar dispersion characteristics.

A Climatology of Nocturnal Low-Level Jets at Cabauw

“…The availability of long-term observations makes the Cabauw site well suitable for deriving climatological information (Van Ulden and Wieringa 1996). Other studies that provide LLJ climatologies are Kurzeja et al (1991), Whiteman et al (1997), andSong et al (2005).…”

Exploring the Possible Role of Small-Scale Terrain Drag on Stable Boundary Layers over Land

“…The role of propagating gravity waves in the ABL dynamics is actively discussed (e.g., Finnigan 1999;Brown et al 2003). Although specific knowledge of waves in the SBL is limited, there is sufficient observational (e.g., Kurzeja et al 1991;Nappo 1991;Sun et al 2003;Cheng et al 2005) and theoretical (Chimonas and Nappo 1989;Nappo and Chimonas 1992;Belcher and Wood 1996) evidence to suggest that gravity waves are important. Since waves generate Reynolds stresses, they might play an important role on the dynamical evolution of the SBL (Einaudi and Finnigan 1981;Finnigan 1999).…”

Wind Climate Analyses for National Weather Service Stations in the Southeast

“…8 and 9) show significant increases in sea breeze occurrences. Indeed, the sea breeze is strongly evident as far inland as AGS (≈ 200-km inland, as seen in simulations by Buckley and Kurzeja, 1997, and described by Kurzeja, Berman, and Weber, 1991).…”