bore mission of 4 June

First eventHomestead observations only

leading wave @ Homestead at 6:45 Z

First event

Note limited surface cooling, for the first bore event. 

Dynamic cooling is superimposed on radiative cooling, sunset is at 2:00 Z, sunrise at 11:30 Z

The real dynamic cooling occurs 2 hours after the second bore event.

“first” bore“second” bore

7 Z AERI sounding

Radiative cooling

another bore??

First event

Three amplitude-ordered waves, the first one the tallest - this suggests a mature bore system. However there is one low-amplitude wave ahead, also seen by MAPR

FM-CW 6-8 Z

ISS1 location: at Homestead

First a 2 mb pressure jump associated with bore, then some waves

Cold front??

1st event 2nd event

this suggests some vertical mixing

7:02 Z

Amplitude-ordered wave train - but first wave seems smallest?? Anyway, this image is consistent with FM CW

second eventleading wave @ Homestead at 10:50 Z

UWKA/WCR data

“second” bore

cold front

Cold-frontal passage near 12:30 Z ??

This may or may not be the same event. ~90 km in 3h45m implies a speed of 6.7 m/s

DDC wsr-88d17:04Z

12:0011:00

FM-CW 10-13 Z

10:50: first UWKA leg over Homestead

1000

1500 m AGL

Is this real??

Cold-frontal passage around 12:50 Z

10:50: first UWKA leg over Homestead

10:50: strong, gusty winds were reported by a person on the ground at Homestead

10 Z

12 Z

11 Z

13 Z

considerable cooling 700-

910 mb

parent density

current??

inversion suggests calm conditions

AERI soundings

WCR nadirantenna reflectivity

Time (UTC)Flight level: 1850 m AGL

Height below flight level(m)

June 4 2002

dBZ

Homestead

Homestead

FLIGHT LEVEL DATA ON THE NEXT PAGE

Some wave activity ??

the ground

WCR echo strength is very weak at night, compared to the daytime CBL …

Aspect ratio: 1:4

temperature

potential temperature

vertical air velocity static pressure

(u,v)

theta-e

mixing ratio

• BORE:• The sustained nature of the change, ahead of a much

more shallow gravity current, suggests that this is a bore.

• This flt level (1850 m AGL) seems to penetrate the bore: the flt level temp behind the bore is some 3 K less.

• This suggests that the waves are deeper than what FM-CW suggests

• Consistent with AERI, the air is more humid behind the bore, with some 4 g/kg more water vapor. However the cooling may NOT be consistent with AERI.

• The net effect is a higher e behind the bore, about 5 K higher.

• WAVETRAIN:• The covariance of and T imply that the aircraft

didn’t bob up & down in a stratified, undisturbed environment, but rather that the aircraft was rather level in a wavetrain

• The waves are ranked in amplitude, the first one the highest amplitude, and they may be ranked in wavelength, the first one the shortest; this is consistent with FM-CW & MAPR

• The vertical drafts have a magnitude of ~2 m/s or less.

• Assume that this is simultaneous transect. The coldest air has seen a history of ascent, so the wave must move forwards.

• The pressure variations at this level are mainly a response of the aircraft to the vertical motion field in which it is embedded, flying from right to left. A 1 m/s updraft during 20 sec is 20 m ascent or 2 mb hydrostatic pressure decrease.

SE NW

c w

Wave propagation

Homestead

SENW

Homestead

Where is the trailing wavetrain?It may be further to the SE - unfortunately this is the end of this flight leg

Flight level ~250 m

Wave crest ahead of cold front??

SE NWFlight level ~160 m

Cold front wave trofs on the cold-frontal surface?

Prefrontal updraft/cooling

Homestead

Cold front

frontal motion

Cold front reaches Homestead ~12:50, ie 60 min later over 30 km, ie the frontal speed is ~ 8 m/s

Cold front wave trofs on the cold-frontal surface?

Prefrontal updraft/cooling

VHF radio interference

WCR nadirantenna reflectivity

Time (UTC)

Flight level: 160 m AGL

dBZAspect ratio: 1:4

WC zenithantenna reflectivity

Height above flight level(m)

SE NW

WCR up-looking

WCR nadirantenna reflectivity

Time (UTC)

Flight level: 750 m AGL

June 4 2002

dBZ

Height below flight level(m)

Homestead

The wave crests were associated with shallow lenticular clouds, and cloud droplets may explain some of the echo. It is not clear what the continuous fine line is.

SENW

Aspect ratio: 1:4

cold front below (<750 m deep)

Conclusion for the 11:57-12:10 leg:

I suspect that this is a gravity wavetrain above the cold frontal surface. The highest amplitude wave appears to be just ahead of the sfc cold front, separated by some 15 km. Perhaps this is the beginning of a new bore?

SENW

wave propagation another low-amplitude wave ?

Homestead

Flight level: 750 m