3-1

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