Cloud Evolution and the Sea Cloud Evolution and the Sea Breeze FrontBreeze Front

Jennifer Bewley

Dept. of Marine and Environmental Systems

Florida Institute of Technology

Melbourne, FL 32901

OverviewOverview

• What is a sea breeze?• What is a sea breeze front?• Satellite Cloud Edge• Radar Thin Line• Why study sea breezes?• Objectives• Method• Data• Synoptic Setting• Results• Conclusions• Questions

Background InformationBackground Information• What is a sea breeze (SB)?

– Differential heating between land and sea– Formation of a thermal low over the land and a

thermal high over the water– A pressure gradient forms, air flows from high to low

pressure– Creates the sea breeze– Opposite effect happens at night creating the land

breeze

• What is a sea breeze front (SBF)?– The leading edge of the sea breeze– A drop in temperature, a wind shift, and an increase in

relative humidity occurs behind the front

Sea Breeze CirculationSea Breeze Circulation

Source: <http://www.bom.gov.au/weather/nsw/amfs/Sea%20Breeze.shtml>

Background Info. Continued…Background Info. Continued…

• Satellite Cloud Edge– Seen on visible or

infrared satellite images

– A line of cumulus clouds, parallel to the shore, with no more clouds on the seaward side of the line of development

Background Info. Continued…Background Info. Continued…

• Radar Thin Line– A region of enhanced radar reflectivity in the optically clear

boundary layer detected by a sensitive Doppler radar – Intense mixing of land and marine air provides several

interfaces capable of reflecting radio energy

Why Study Sea Breezes?Why Study Sea Breezes?

• Forecasting– Changes temperature, wind speed and direction, and

relative humidity

• Convection, Clouds, Turbulence• Climate Modeling

– Formation of clouds

• Renewable Energy– Wind and solar energy

• Operationally, how can you accurately locate the SBF?

ObjectivesObjectives

• To compare the location of the satellite cloud edge to the surface sea breeze front and the location of the radar thin line

• To analyze the differences in the location of the indicated features and create a possible vertical profile of the sea breeze front

MethodMethod• Team Beach

– Melbourne Beach– Measured air

temperature, RH, and wind speed every 15 mins.

– Sky observations, water temperature, wave height and period, salinity, and dissolved oxygen were taken every 30 mins.

• Team FIT – Collected data

Method Continued…Method Continued…

• Team Mobile Unit– Traveled west on 192, attempting to transect the SBF– The mobile unit was equipped with a wind vane, cup

anemometer, and radiometer.– Wind speeds, RH, air temperature, sky observations,

percent cloud cover and wind direction were recorded.

Method Continued…Method Continued…

DataData

• Team Beach & Team Mobile Unit– Wind speed and direction

• Team FIT– GOES 4 km visible satellite

imagery – Melbourne NWS Doppler

radar base reflectivity images

– Other surface observations

Synoptic SettingSynoptic Setting

Synoptic SettingSynoptic Setting

Synoptic SettingSynoptic Setting

ResultsResults

• Analyzed the progression of the cloud edge, thin line, and the surface fronts

• Developed a model to find the relation of the features for each day

Results Continued…Results Continued…

Location

Time Distance

Date Radar Cloud Edge Radar Cloud EdgeMay 25* N/A 25 mins behind

surface front

N/A 6.9 km behind

surface front

May 26 N/A 75 mins behind

surface front

N/A 8.1 km behind

surface front

May 27 50 mins ahead

surface front

10 mins behind

surface front

1.5 km ahead

surface front

1.7 km behind

surface front

May 25* = Strong easterly flow

May 25May 25

May 26May 26

May 27May 27

ConclusionsConclusions

• The thin line precedes the surface front which precedes the cloud edge

• The actual distances between these features vary and depend on several factors – Operationally, the satellite cloud edge may not always

be a good indication of the location of the surface SBF

• One improvement would be to have higher resolution data, especially satellite and radar imagery and more sampling sites

AcknowledgementsAcknowledgements• A special thanks to…

– Mr. Splitt for advising this project and aiding with the creation of figures

– Mr. Leslie for the mobile renewable energy station

– Andrew Condon for the synoptic maps

– All the MFP students and TA’s for helping with the data collection

Questions?Questions?

Brian ZachryBrian Zachry