Transcript MFP_andrew_condon - Florida Institute of Technology

Hypothesized Thermal
Circulation Cell
Associated with the Gulf
Stream
Andrew Condon
Department of Marine and Environmental Systems
Florida Institute of Technology
Melbourne, FL 32901
July 15, 2004
Overview
Objectives
 What is a Thermal Circulation Cell?
 Ingredients of Cloud Formation
 Possible Gulf Stream Circulation Cell
 Data Collection Methods
 How do we know if it is there? / Results
 What influences its formation?
 Summary

Objectives
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To determine whether or
not a secondary thermal
circulation cell due to the
offshore sea surface
temperature gradient
associated with the Gulf
Stream exists
If it does exist how can
it be identified and what
strengthens and hinders
its formation
Why

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Not well documented,
very little research
conducted in this area
Implications for Marine
Meteorology / air-sea
interaction
Marine Interests
(recreational and
commercial): Clouds or
thunderstorms along
Gulf Stream
Thermally-Forced Circulations
Mesoscale (10’s-100’s km / hours)
 Differential Heating: Temperature Contrast
 Cooler more dense air causes higher pressure
than warmer less dense air
 Pressure gradient exists and the wind starts to
blow from high to low pressure

Thermal Circulation

Example: The Sea-Breeze
Ingredients for Cloud Development

Lift
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Convection (Thermals)
Orographic
Convergence
Frontal
Temperature
Moisture
Possible Gulf Stream Circulation
Cell?
Data Collection Methods
Data Collected May 25, 26, and 27 2004
 Visible Satellite Images from Global Hydrology
and Climate Center
 Omega Cross Sections using GARP
 MODIS Satellite Images for the Gulf Stream
Location
 RUC 850 mb Height and Wind Analysis
 Surface and buoy temperature observations

Gulf Stream Location
Results
Day One Visible Satellite Image
Day Two Visible Satellite Image
Day Three Visible Satellite Image
Omega Cross Sections

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dp

dt
The time rate of change of pressure following an
individual air parcel
Since pressure decreases with height, negative omega
indicates rising motion positive omega indicates sinking
motion
Day One Omega (Vertical Velocity)
Pressure (mb)
3.5 km
Location
Day Two Omega (Vertical Velocity)
Pressure (mb)
3.5 km
Location
Day Three Omega (Vertical Velocity)
Pressure (mb)
3.5 km
Location
Why does it form?
Convective Inhibition (J/kg)
Time (UTC) May 25
May 26
May 27
0900
0
-303
-248
1500
NA
-606
-179
2100
NA
-407
-108
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CINH - A measure of the amount of energy needed in order to initiate
convection or how unlikely thunderstorm development may be
The more negative the CINH in the sounding, the greater the atmospheric
stability and lesser the chance of vigorous convection
Synoptic Flow
Day One: High pressure ridge to north, easterly
flow
 Day Two: Ridge slides south, more westerly
flow
 Day Three: Ridge to the south, westerly flow
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10
Temperature
Difference between
Land and Cold Pool
8
6
4
2
Temperature
Difference between
Gulf Stream and Cold
Pool
0
-2
22
16
11
3
19
11
4
23
16
12
-4
2
Temperature Differences (C)
Why Does the Sea Breeze Cell
Peak on
Dominate
Day one
Time (UTC) Starting 0200 UTC May 25,
2004
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Magnitude of temperature difference between the land and cold pool is much
greater than the difference between the Gulf Stream and the cold pool
Day one saw largest difference between Gulf Stream and cold pool, land and
cold pool temperature difference remains fairly constant
Day One: Possible Scenario
Summary
Gulf Stream circulation cell was present on day
one, but was not present on days two and three
 Easterly flow is helpful for Gulf Stream
circulation cell formation
 Westerly winds cause the sea breeze cell to
dominate over the smaller Gulf Stream cell
 Low and mid-level moisture and temperature
profiles are important for cloud development
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Acknowledgements
Professor Michael Splitt for all his knowledge
and input
 Nicole Botto for the land – water temperature
differences data
 Fellow MFP students for help with data
collection
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Questions?