Shapiro, M. A., 1984: Meteorological tower measurements of a surface cold front. Mon. Wea. Rev., 112, 1634-1639. Shapiro (1984)

Shapiro, M. A., 1984: Meteorological tower measurements of a surface cold front. Mon. Wea. Rev., 112, 1634-1639.

Shapiro (1984)

BAO tower

WNW downslope

flow

Temperatures (°C)winds (barb = 10 kts)

The passage of a strong cold front in eastern Colorado

We will be interested in the structure of this front as it passes the

Boulder Atmospheric Observatory tower

The Boulder Atmospheric Observatory Tower located in Erie, Colorado near I-25

Cross section of the cold front that passed the BAO tower on 24 March 1982

Based on a rawinsonde at Denver, a radiometer temperature profile, a lidar wind profile and surface data

Potential temperature (K, solid) and front normal wind component (m/s, dashed)

Two minutes!!!

300 meters

superadiabaticlapse rate

Vertical motion (m/s) measured by sonic anemometers on the tower

Frontal boundaries denoted by solid lines

zy

w

xy

u

yy

v

ydt

d

Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence)

Change in potentialtemperature gradient

following parcel

Confluenceacting ongradient

Shearacting ongradient

Tilting of verticalgradient

Can’t evaluate this -so assume negligiblebased on surface data

Do the flow fields suggest that frontal contraction was occurring at the time the front passed the tower?

Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence)

Change in potentialtemperature gradient

following parcel

Confluenceacting ongradient

Shearacting ongradient

Tilting of verticalgradient

confluence term

zy

w

xy

u

yy

v

ydt

d

Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence)

Change in potentialtemperature gradient

following parcel

Confluenceacting ongradient

Shearacting ongradient

Tilting of verticalgradient

Tilting term

zy

w

xy

u

yy

v

ydt

d

Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence)

Change in potentialtemperature gradient

following parcel

Confluenceacting ongradient

Shearacting ongradient

Tilting of verticalgradient

Total frontogenesis

0

0

ydt

d

ydt

d

Frontolytical

Frontogenetical

zy

w

xy

u

yy

v

ydt

d