How does the Sea-Breeze affect Convection?

699 reads

By Steven Schmidt on July 13, 2012, 3:16pm

Use your ← → (arrow) keys to browse more stories.

For those of you who read my previous article “What’s the temperature of rain?”, I have a correction. The right hand side of equation 2 should be divided by the sum of the rain’s mass, M_R, and the bucket’s original water mass, M_B. Sorry, my bad. :-/

Anyway, let’s get to talking about sea-breezes and convection!

A couple months ago I had to analyze approximately three months worth of METAR sky cover data for the validation of cloud fraction estimates I produced during my master’s thesis. The time period I was analyzing was from June 1^st, 2004 to August 14^th, 2004, and I was using data from LaGuardia, White Plains, Bridgeport, and Westhampton Beach airports.

I noticed immediately after graphing a time series plot of cloud fraction, that the frequency of clear skies appeared to vary significantly between each location. Bridgeport airport had clear sky conditions reported the most while the more western locations (White Plains and La Guardia) appeared to have the least. It didn’t take long to consider a sea-breeze as the cause, but that’s another article all together.

It was at this time that I really started to ponder the affects of a sea-breeze on convection near the shore behind a well-established sea-breeze front. I initially thought that it should enhance it; after all, cold air moving over a hot surface should drive convection right?

Well, my initial thoughts were wrong.

I was kind of puzzled at first when I heard from a friend who’s also a contributor here on WXedge.com that the sea-breeze isn’t good for convection in CT. He stated that it tends to stabilize the environment, inhibiting storm development

A quick sketch on a thermodynamic diagram (the cover photo) quickly cleared things up for me, and I hope it does for anyone who might be in need of some clarification like I did.

In the simple case portrayed in the cover photo, passing of a sea-breeze front causes temperatures near the surface to drop. This decreases the vertical temperature gradient (reference red and blue lines) making the environment near the ground more stable.

References:

Thermodynamic diagram without temp profiles was obtained from the website of Bruce P. Hayden from the University of Virginia at following link…

http://atlantic.evsc.virginia.edu/~bph/book_gifs/CFig_55.gif

Use your ← → (arrow) keys to browse more stories.