Monday, 29 January 2024: 9:45 AM
341 (The Baltimore Convention Center)
Atmospheric air flows near the surface become particularly complex in the very stable
boundary layer (VSBL) as it is typically in Arctic winter/spring. It is common to observe
alternating events between quiescent periods, with almost complete suppression of
turbulence due to atmospheric stratification, and short-duration outburst events of strong
turbulence, during which turbulence is reestablished at all scales. This phenomenon is
known as global intermittency. Despite their short duration, these turbulent events may be
responsible for an appreciable fraction of the turbulent transport of mass, energy, and
momentum in the VSBL. Describing the causes of both turbulence onset and collapse during
these events remains a challenge. Their origin may be near the top of the VSBL, propagating
towards the surface, but they may also be generated by interaction with the surface and
propagated upwards. Furthermore, atmospheric models based on the Monin-Obukhov
similarity theory generally fail to reproduce the intermittent behavior of turbulence in the
VSBL. To characterize and understand the occurrence, propagation, and cessation of
intermittent turbulence, this study analyzes data collected as part of the PHOXMELT
((Photochemical Halogen and Ozone eXchange: a Meteorological Experiment on Layered
Turbulence) field campaign during March to May 2016 in Utqiaġvik, Alaska representing the
transition from boreal winter to spring. Data sets comprise measurements made with sonic
anemometers deployed on a 12-meter tower at 8 vertical levels (positioned at 0.5, 1.3, 2.0,
4.0, 5.7, 7.7, 9.7, and 11.6 m), capturing the three components of the wind speed and virtual
temperature acquired at a frequency of 10 Hz. Through classification of the stable boundary
layer regime, the occurrences and the direction of propagation of the intermittent turbulence
events are determined. The onset and cessation of turbulence are analyzed as functions of
both local wind shear and temperature gradients. Furthermore, the behavior of
nondimensional gradients in the VSBL is addressed.
boundary layer (VSBL) as it is typically in Arctic winter/spring. It is common to observe
alternating events between quiescent periods, with almost complete suppression of
turbulence due to atmospheric stratification, and short-duration outburst events of strong
turbulence, during which turbulence is reestablished at all scales. This phenomenon is
known as global intermittency. Despite their short duration, these turbulent events may be
responsible for an appreciable fraction of the turbulent transport of mass, energy, and
momentum in the VSBL. Describing the causes of both turbulence onset and collapse during
these events remains a challenge. Their origin may be near the top of the VSBL, propagating
towards the surface, but they may also be generated by interaction with the surface and
propagated upwards. Furthermore, atmospheric models based on the Monin-Obukhov
similarity theory generally fail to reproduce the intermittent behavior of turbulence in the
VSBL. To characterize and understand the occurrence, propagation, and cessation of
intermittent turbulence, this study analyzes data collected as part of the PHOXMELT
((Photochemical Halogen and Ozone eXchange: a Meteorological Experiment on Layered
Turbulence) field campaign during March to May 2016 in Utqiaġvik, Alaska representing the
transition from boreal winter to spring. Data sets comprise measurements made with sonic
anemometers deployed on a 12-meter tower at 8 vertical levels (positioned at 0.5, 1.3, 2.0,
4.0, 5.7, 7.7, 9.7, and 11.6 m), capturing the three components of the wind speed and virtual
temperature acquired at a frequency of 10 Hz. Through classification of the stable boundary
layer regime, the occurrences and the direction of propagation of the intermittent turbulence
events are determined. The onset and cessation of turbulence are analyzed as functions of
both local wind shear and temperature gradients. Furthermore, the behavior of
nondimensional gradients in the VSBL is addressed.
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