1. WAVES AND INTERMITTENT TURBULENCE IN THE STABLE PBL
Carmen Nappo
Knoxville, TN 37919

2. OBJECTIVE
EXAMINE THE CORRESPONDENCE BETWEEN EPISODES OF INTERMITTENT TURBULENCE AND GRAVITY WAVES.

3. NUMERICAL ANALYSIS
IDENTIFY WAVE-LIKE DISTURBANCES USING WAVELET ANALYSES
BAND-PASS FILTER SURFACE PRESSURE DATA
CALCULATE WAVE SPEED AND DIRECTION
ROTATE COORDINATES SO THAT X-AXIS IS PARALLEL TO WAVE VECTOR
CALCULATE TURBULENCE FLUXES OVER 30-s INTERVALS AND THEN AVERAGE THESE OVER CONSECUTIVE WAVE PERIODS
PLOT TOWER PROFILES DURING WAVE AND NON-WAVE PERIODS

4. CASES-99 NIGHTS
06 October : Blumen et al (2001), Newsom and Banta (2003)
14 October : Fritts et al. (2003)
18 October : Sun et al. (2002), Sun et al (2004)

5. 6 OCTOBER RICHARDSON NUMBER 45 - 55 m
Moderate to weekly stable.

6. WAVELET ANALYSIS PERIOD 1 PERIOD 3 PERIOD 2
Periods 1,2 and 3 observed and analyzed by Blumen (2001), Newsome and Banta (2003). A VERY DISTURBED NIGHT.
PERIOD 2

7. LAG ANALYSIS : 06 OCT. 19 75˚ 22×103 1.5 (1.0) 2.5 (5.1) 46˚ (36˚)
TIME (UTC)
AVERAGE PERIOD (min)
SPEED
(ms-1)
DIRECTION
WAVELENGTH (m)
04:45 - 5:30
PERIOD 1 19
15-23 min filter
75˚
22×103
05: :40
PERIOD 2
1.5 (1.0)
1-3 min filter
2.5 (5.1)
46˚ (36˚)
225 (299)
06: :40
PERIOD 3 14
11-17 min filter
65
12103

8. FLUX PROFILES 06 OCTOBER

9. FLUX PROFILES 06 OCTOBER

10. 14 OCTOBER RICHARDSON NUMBER 45 – 55 m
Uniform stability.

11. 14 OCTOBER
07:20
06:30
05:45
03:15
DUCTED GRAVITY WAVES WITH PERIODS BETWEEN 2 AND 7 MINUTES.

12. LAG ANALYSIS : 14 OCT. 2-7 min BAND-PASS FILTER
TIME (UTC)
AVERAGE PERIOD (min)
SPEED
(ms-1)
PROPAGATION
DIRECTION
WAVELENGTH (m)
03: :00
4.5 7
221
1800
05: :00 11
245
3000
06: :00
320
07: :00 15
313
4000
We consider these disturbances discontinuous parts of a wave duct which is changing slightly with time.

13. TURBULENCE FLUX 14 OCTOBER
FLUXES ARE CALCULATED OVER AN 18-MINUTE AVERAGE. BAND-PASS FILTER IS 2 – 7 MIN FOR ALL CALCULATIONS. RED LINE IS FOR ‘NO WAVE’ PERIOD.

14. TURBULENCE FLUX 14 OCTOBER
FLUXES ARE CALCULATED OVER AN 18-MINUTE AVERAGE. BAND-PASS FILTER IS 2 – 7 MIN FOR ALL CALCULATIONS. RED LINE IS FOR ‘NO WAVE’ PERIOD.

15. 18 OCTOBER RICHARDSON NUMBER 45 – 55 m
Moderately variable stability.

16. 18 OCTOBER Lag analysis using 10-20 min data
C=6 ms-1, θ=293, length=5400 m, period=15 min
EVENTS III REPORTED BY SUN ET AL.
Sun, et al. (2004). C=2.3 ms-1, θ=273, length=1350 m, period=10 min

17. TURBULENCE FLUX 18 OCTOBER

18. TURBULENCE FLUX 18 OCTOBER
The density currents appear to have a stronger effect on the turbulence than the wave-like disturbances. The wave disturbances may be associated with the density currents.

19. CONCLUSIONS
WAVELET ANALYSES MAY BE A USEFUL TOOL FOR COMPILING STATISTICS ON WAVE-TURBULENCE INTERACTIONS, ESPECIALLY DURING PERIODS OF WAVE BREAKING.
HOWEVER, NOT ALL PERIODS OF LARGE WAVELET-ENERGY-DENSITY ARE ASSOCIATED WITH GRAVITY WAVES AND INTERMITTENT TURBULENCE. MORE DATA ANALYSIS IS REQUIRED.
A QUANTITATIVE RELATION BETWEEN WAVE AMPLITUDES, PBL STABILITY, AND TURBULENCE INTENSITY MAY BE POSSIBLE.
WAVE INSTABILITY RESULTS IN MUCH GREATER TURBULENCE IN THE PBL THAN DUCTED INTERNAL WAVES.