1. Rawinsonde Kite Profiles
LT Dave Kuehn
18 Sep 2002

2. Comparing Kite Profiles to Bulk Method (Fairall 1996)
Why
Evap duct
Operational significance
How
Brief overview on methods
Matlab program
What
Results
Kite data vs. Bulk Method

3. Ducting Height (m) M 300 200 100 Elevated Duct Surface-based Duct
Surface-based
Duct
Height (m)
Evaporation Duct M

4. Evaporation Duct 15 10 5 Z*
Height (m)
Evap
Duct M
RH (%)

5. Propagation Loss for Radar Within Evaporation Duct
Duct Ht = 65 ft, 55 ft
Greatly Increased Detection Ranges Possible
Duct

6. Method and Manipulation
Program assumes height based on press
Negative heights not possible
Modify based on in-situ height and time recordings (purple line)

7. Method and Manipulation
Select bad data (purple)
Ship influence
Readings prior to launch
Kite dipping
Green is ship data
Difference in press and RH

8. Method and Manipulation
Select interval average based on similar airmass characteristics
Pot Temp and RH and M profile data
(red marks)

9. Average over selected interval
Select average air temp, sea temp and RH
Fairall’s Bulk Method derived Pot Temp, RH and M profile (black line)
Mean kite data over interval (lavender circles)

10. Results 17 July

11. Results 17 July

12. Results 19 July 2002 1945 - 1955 Evap duct present later in
afternoon on 19 July.
Coincides closely with Rh
gradient.
Evap first noted at 1910 on 19 July

13. Results 19 July 1845 - 2010 Evap No duct duct Evap Evap Duct duct
One average period fits bulk method better than smaller periods
Evap
Duct
~1910
Evap
duct

14. Conclusions: Subjective Error
Surface height, kite height, sonde response, contaminated averages, air temp vs sea temp
Bulk Method did not represent atmosphere well, high atmospheric variability (esp RH)
Bulk Method always shows duct height 6-9 meters. Kite did not.
When duct was measured (starting 1910 on 19 July) Bulk Method generally showed a lower duct height (7 meters) than kite data (11+ meters)
Evap ducts of <1-2m extremely difficult to detect