Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Surprising Transition in Atmospheric Boundary Layer Turbulence
  Structure from Neutral to Moderately Convective Stability States and
  Mechanisms Underlying Large-scale Rolls   The vectoral wind structure of daytime atmospheric boundary layer (ABL)
turbulence is strongly dependent on the balance between shear-driven turbulence
production of horizontal fluctuations (driven by winds at the mesoscale), and
buoyancy-driven turbulence production of vertical velocity fluctuations (driven
by solar heating), characterized by the global instability state parameter
$-z_i/L > 0$. In the fully shear-driven neutral limit $-z_i/L \rightarrow 0$,
the surface layer is dominated by coherent streamwise-elongated concentrations
of negative streamwise fluctuating velocity (low-speed streaks), while in the
moderately convective state ($z_i/L \sim 10$ ) buoyancy generates
streamwise-elongated thermal updraft sheets of concentrated vertical velocity
fluctuations. Using large-eddy simulation (LES), we study the transition
between the neutral and moderately convective states by quantifying
correlations and integral scales as a function of $-z_i/L$ created by
systematically increasing surface heat flux with fixed geostrophic wind. We
discover a surprising sudden transition in ABL turbulence structure at $-z_i/L
\approx 0.40$ with dramatic enhancement of streamwise coherence, particularly
in the mixed layer, and a sudden change in ABL dynamic response to further
increase in surface heating. In the supercritical ABL, continued increase in
surface heat flux leads to a maximal coherence state at ($z_i/L \sim 1.0-1.5$)
associated with helical large-scale roll structure and exceptionally coherent
thermal updrafts, a process driven by two key dynamical effects: (a) a
surprising continual increase in streamwise coherence of streamwise velocity
fluctuations and shear-driven low-speed streaks and (b) increasing spatial
correlation between the coherent low-speed streaks in the surface layer below
and in the coherent thermal updrafts with in the mixed layer above.

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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: cs
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The categories of this paper are: ao-sci