This study analyzed a sea breeze boundary that occurred on June 12th in Florida using radar observations, satellite imagery, and ground measurements. Radar detected a thin line 19 kilometers ahead of the observed sea breeze passage. It took the radar-observed boundary two hours to reach the ground observation point. The radar thin line was likely caused by insects rather than marking the true sea breeze boundary location near the surface. The results suggest radar can observe sea breeze boundaries ahead of their actual surface location.

1. An Analysis of a Sea
Breeze Boundary in
Florida
James Brownlee
Florida Institute of Technology
Department of Marine and Environmental Systems

2. Outline of Talk
• Introduction to Sea Breezes
• Radar and Sea Breeze Detection
• Goals of this study
• Methods and the area where the June 12th Sea Breeze was
captured
• Analysis of Radar, Satellite, and Ground Observations of the
Sea Breeze
• Insects or Clouds?
• Conclusion/Implications

3. Introduction
• What is a sea breeze?
• An onshore wind that develops along the coastline.
• It is driven by the temperature contrast between the land and
sea.
• Sea Breeze Circulations can reach 50 to 100 km horizontally.
• Vertically they typically reach 300 to 700 meters.

4. Figure 1: A “ideal” diagram of a sea breeze circulation. (Image taken from NWS Jetstream)

5. Figure 2: This shows the horizontal and vertical dimensions of a sea breeze
circulation. (Image taken from Tijm et al., 1999)
Ocean Land

6. Radar Observations of Sea Breezes
• Radar is typically used to detect areas of precipitation, but it
can also detect echoes that are not due to clouds or
precipitation.
• Such radar returns are known as clear air echoes.
• Radar thin lines associated with sea breezes are a very
common example of a clear air echo returns.
• Much debate exists over what causes these radar thin lines.

7. Questions/Goals
• Question 1: Is the sea breeze thin line that is observed on
radar represent where the surface boundary is located?
• Question 2: What is responsible for the radar observed thin
line that is associated with the sea breeze boundary?
• These two questions were addressed while tracking the sea
breeze boundary on June 12th.

8. June 12th Sea Breeze Study
On June 12th, the sea breeze was sampled using the AIRMAR PB
200 weather sensor.
It was tracked on the ground from Melbourne to Kissimmee.
This tracking started at 12:34 PM and ended at 5:54 PM.
A final combination of these ground observations along with
radar and satellite imagery were used to analyze this sea breeze
boundary.

9. • Figure 3: This is the AIRMAR sensor that was used capture the sea breeze passage.

10. • Figure 4: This shows how far inland the sea breeze went (Image taken from Google Maps).
50 km

11. Ground and Radar Observations of
the Sea Breeze.
Figure 5: At 3:05 PM, the sea breeze boundary passed the van as it was stationary along
US-192.
-3
-2
-1
0
1
2
3
18:40:00 18:50:00 19:00:00 19:10:00 19:20:00 19:30:00 19:40:00
Ucomponentofthewindinm/s
Time (UTC)
Sea Breeze Passage at 3:05 PM

12. Figure 6: This is a radar image of the radar thin line taken at 3:05 PM. The red arrow indicates the
location of the thin line. This image was captured at a radar elevation angle of 0.48 degrees.
Radar Thin Line

13. • Figure 7: This shows the horizontal distance between where the van and the radar saw the sea
breeze boundary at 3:05 PM.
19 Kilometers
Van
Location
Thin Line
Location

14. • Figure 8: This shows how far apart radar and surface observations of the sea breeze boundary
are. AGL = above ground level SB = sea breeze
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 5 10 15 20
VerticalHeight(km)
Horizontal Distance (km)
Surface and Radar Observations of the Sea Breeze Front at 3:05
PM
Radar Observed SB: 19.2 km east; 0.5 km AGL
Radar Observed SB: 19.7 km east; 0.7 km AGL
Radar Observed SB: 18.7 km east; 0.2km AGL
Ground Observation of SB

15. Figure 9: It took approximately 2 hours for the radar observed sea breeze to reach the ground
location where the sea breeze passage had previously been observed.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 5 10 15 20
VerticalHeight(km)
Horizontal Distance (km)
T ~ 2 Hrs.

16. Insects or Clouds?
• Figure 10: Radar scan of the sea breeze thin line at 5:29 PM. This was taken at an elevation
angle of 0.47 degrees.
Radar
Thin
Line

17. • Figure 11: Differential reflectivity radar scan at 5:29 PM. This image was captured at an
elevation angle of 0.50 degrees.
Radar
Thin
Line
Thunderstorms

18. • Figure 12: 1 km resolution visible satellite image captured at 5:31 PM.
Little Cloud
Development

19. • Figure 13
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 5 10 15 20
VerticalHeight(km)
Horizontal Distance (km)
Is this actually the sea breeze boundary?

20. Figure 14: (Image taken from NWS Jetstream)
Possible Location of the
Thin Line

21. Conclusion and Implications
• The results of this study suggest three things:
• 1. This study shows that there can be a large horizontal
distance between ground and radar observations of a sea
breeze boundary.
• 2. The radar thin line may have been caused by insects.
• 3. The radar thin line may not mark the true location of the
sea breeze boundary near the surface or aloft.

22. Acknowledgments
• Thanks to Mr. Splitt for his guidance on this project.
• Robby, for all the van driving.
• The Department of Marine and Environmental Systems at FIT
for funding this project.

23. Questions?

24. References
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review. Aust. Met. Mag., 41: 7-19, 1992.
•
Atkins, N. T. and R. M. Wakimoto. Influence of the Synoptic-Scale Flow on
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•
Atkins, N. T., R. M. Wakimoto, and T. M. Weckwerth. Observations of the
Sea-Breeze Front during CaPE. Part II: Dual-Doppler and Aircraft Analysis.
Mon. Wea. Rev., 123: 944-969, 1995.
Google. Google Maps. 2012. Web. 27 June 2012.
<https://maps.google.com/maps?hl=en>

25. Google. Google Maps. 2012. Web. 27 June 2012.
<https://maps.google.com/maps?hl=en>
Simpson, J. E. Sea Breeze and Local Wind. Cambridge University Press,
Cambridge/New York/Melbourne, 234 pp., 1994.
Sharp, J. Clear-air Radar Observations and their Application in Analysis of Sea
Breezes. University of Washington: Department of Atmospheric Sciences.
1997. 28 June 2012.
http://www.atmos.washington.edu/~justin/radar_project/introduc.htm
“The Sea Breeze”. NWS Jet Stream. 13 Jul. 2012 Web. 15 Jul. 2012.
Tijm, A. B. C., A. A. M. Holtslay., and A. J. Van Delden. Observations and
Modeling of the Sea Breeze with the Return Current. Mon. Wea. Rev., 127:
625-640, 1999.