cloud evolution and the sea breeze front

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