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3-1. NCAR’s IBM SP4 `` Bluesky ” with 1600 Processors. 3-2. 3-3. 3-4. CLASSIFICATION OF CLEAR PBLs. 3-5. CLASSIFICATION OF CLEAR PBLs. Neutral. -10. -3. 0. 2. Strong convective forcing. Mix of shear and buoyancy forcing. Weakly stable continuous turbulence. - PowerPoint PPT Presentation
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3-1
NCAR’s IBM SP4 ``Bluesky” with 1600 Processors
3-2
3-3
3-4
CLASSIFICATION OF CLEAR PBLs
3-5
Strong convective forcing
-3 0 2
Mix of shear and buoyancy forcing
-10
Weakly stable continuous turbulence
Strongly stable globally intermittent or collapsed turbulence?
Neutral
CLASSIFICATION OF CLEAR PBLs
3-6
Plumes visualized in laboratory convection
3-7
3-8
VISUALIZATION OF VERTICAL VELOCITY IN X-Y PLANES
Z = 47m
20km 3-9
VISUALIZATION OF VERTICAL VELOCITY IN X-Y PLANES
Z = 156m
3-10
VISUALIZATION OF VERTICAL VELOCITY IN X-Y PLANES
Z = 390m
3-11
VISUALIZATION OF VERTICAL VELOCITY IN X-Y PLANES
Z = 547m
3-12
VISUALIZATION OF VERTICAL VELOCITY IN X-Y PLANES
Z = 718m
3-13
VISUALIZATION OF VERTICAL VELOCITY
Narrow fast updrafts
Wide slow downdrafts
Horizontal convergence
3-14
3-15
x-y average TKE in mid-pbl
stationary periodtransient growth
3-16
w-skewness, biased towards updrafts
LESLES
w-variance, mid-PBL maximum
?
3-17
Mean KE
Total KE
Turbulent transport Shear production Buoyancy production Pressure transport Dissipation
3-18
3-19
3-20
Time
Initial profile
Overshoot and steeper gradient
3-21
VISUALIZATION OF T PERTURBATION IN X-Y PLANES
Z = 47m
20km
Hot cores
3-22
VISUALIZATION OF T PERTURBATION IN X-Y PLANES
Z = 718m
Cold cores
3-23
VISUALIZATION OF T PERTURBATION IN X-Y PLANES
Z = 781m
Cold cores
3-24
VISUALIZATION OF T PERTURBATION IN X-Z PLANES
20km
Entrainment sites
Stiff gradient at top of plumes
3-25
PBL ENTRAINMENT
Entrainment “zone”
3-26
Coherent structures visualized in a neutral flat wall boundary layer in a wind tunnel.
Entrainment hummocks in an x-z plane. Low-speed streaks in an x-y plane.
-3 0 2-10
Neutral
CLASSIFICATION OF CLEAR PBLs3-27
Horizontal (x-y) slice of vertical velocity at z = 25m from an LES of a PBL driven by large scale forcing from the mesoscale code COAMPS. Atmospheric stability zi/L varies from strongly unstable to near neutral over the course of the 8 hour simulation. This changes the dominant coherent structure in the PBL from a hexagon to a streaky pattern.
3-28
MEAN AND TURBULENT FLUX PROFILES FOR PBLS WITH VARYING STRATIFICATION
LES RESULTS MOENG & SULLIVAN (1994)
3-29
STABLE NIGHTTIME PBL
Continuous turbulence
Transient turbulence with collapse
Radiatively cooled very weak turbulence
Time series of sensible (turbulent) heat flux H from CASES-99 [Van de Wiel, 2003]
sunset sunrise
Radiation
3-30
STABLE BOUNDARY LAYER
w contours
Wind profile
Heat flux profile
400m
Low level jet
KH mixing
3-31
3-32