Baroclinicity adds another layer of complexity to the much-studied barotropic atmospheric boundary layers (ABLs) by modulating the pressure gradient in height. Despite the prevalence of baroclinicity in real-world ABLs, our knowledge of the interacting effects of baroclinicity and atmospheric stability is limited. In this talk, we aim to address this knowledge gap by systematically varying baroclinicity and stability using the large-eddy simulation (LES) technique.
We will present how baroclinicity alters the friction velocity, Obukhov length, shear production, ABL height, and low-level jet (LLJ) in diabatic baroclinic atmospheric flows. It will be shown that while baroclinicity significantly impacts unstable, neutral, and weakly stable ABLs, its effects reduce with increased stratification in the ABL. In strongly stratified ABLs, the LLJ height, friction velocity, and Obukhov length converge to a constant asymptote independent of the baroclinicity regime. We will demonstrate that this behavior is attributed to the strong turbulence destruction in very stable ABLs that decouples the surface from higher elevations where baroclinicity is more important.
Finally, two rescaling methods in the inner and outer layers of stable baroclinic ABLs will be presented to non-dimensionalize and collapse the wind profiles in baroclinic environments. The developed reduced model for different baroclinic wind profiles will be shown against the LES results. The findings of this research elucidate the underlying physics of baroclinic diabatic ABLs and are useful for characterizing the wind profiles in weather/climate models, field measurements, and various industrial applications.
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This content will become publicly available on May 18, 2024
Effects of Low‐Level Jets on Near‐Surface Turbulence and Wind Direction Changes in the Nocturnal Boundary Layer
In this study we examined a data set of nearly two‐year collection and investigated the effects of low‐level jets (LLJ) on near‐surface turbulence, especially wind direction changes, in the nocturnal boundary layer. Typically, nocturnal boundary layer is thermally stratified and stable. When wind profiles exhibit low gradient (in the absence of LLJ), it is characterized by very weak turbulence and very large, abrupt, but intermittent wind direction changes (∆WD) in the layers near the surface. In contrast, presence of LLJs can cause dramatic changes through inducing wind velocity shears, enhancing vertical mixing, and weakening the thermal stratification underneath. Ultimately, bulk Richardson number (
- NSF-PAR ID:
- 10418442
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 128
- Issue:
- 11
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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