The basic equations - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 85

p Figure 2.18. Evidence of clear-air boundary rolls: (top) as depicted by WSR-88D radar
reflectivity at Oklahoma City, OK on April 6, 2010. The bands of clear air reflectivity are
oriented in the north-northwest to south-southeast direction; the bands of enhanced clear air
reflectivity are regions of enhanced insect concentration where the convergence at the bottom of
the ascending branch of a roll is located. (Bottom) As depicted by a mobile Doppler lidar
(TWOLF) in the Texas Panhandle on May 18, 2010 during VORTEX2. Doppler velocity in
ms 1 ; streaks in Doppler velocity are suggestive of rolls oriented in the north-northwest to
south-southeast direction. The rolls are spaced several hundred meters apart. Streaks in
Doppler velocity are indicative of where vertical transports of momentum increase the wind
speed as a result of vertical shear in the environment (courtesy of Jana Houser).

Figure 2.19. Idealized illustration of the tilting of horizontal vorticity associated with hori-
zontal convective rolls into the vertical by ascending air along a dryline. Horizontal convective
rolls A, B, and C originate on one side of the dryline, while roll D originates on the other side of
the dryline. The dashed circle with arrows represents a horizontal misocyclone (a misocyclone
is smaller than a mesocyclone) along the dryline resulting from the tilting upward of rolls A and
B. The heavy solid line marks the dryline; the thin dotted line marks the moist layer (from
Buban et al. 2007).

as follows:

u 0 p 0 @ =@ t ¼ 1 = @ =@ x ð 2 : 286 Þ

@v 0 p 0 =@ t ¼ 1 = @ =@ y ð 2 : 287 Þ

p 0 0 ¼ B 1 = @ =@ z ð 2 : 288 Þ

t þ N 2 w 0 ¼ Q @ B =@ ð 2 : 289 Þ

u 0 x þ@v 0 w 0 @ =@ =@ y þ@ =@ z ¼ 0 ð 2 : 290 Þ