Hypothesized Thermal Circulation Cell Associated with the Gulf Stream Andrew Condon Department of Marine and Environmental Systems Florida Institute of Technology Melbourne, FL 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 Why Objectives Why  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  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 Example: The Sea-Breeze

Ingredients for Cloud Development  Lift  Convection (Thermals)  Orographic  Convergence  Frontal  Temperature  Moisture

Possible Gulf Stream Circulation Cell?

Data Collection Methods  Data Collected May 25, 26, and  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 Omega Cross Sections  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 NA NA  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

Why Does the Sea Breeze Cell Dominate  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 Peak on Day one

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

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

Questions?