Tuesday, November 13, 2012

What is going on above ground?

Calenques National Park is a corridor for different winds.  The "Mistral Winds" that come in from the Northwest can blow in excess of 90 kilometers per hour and play a heavy role in the climate of Marseille’s entire region, Provence. This wind is commonly seen in winter and spring, but it does make appearances throughout the year anytime that conditions are right. It is caused by high pressure cells that have an anti-cyclonic pattern in the Atlantic Ocean west of France and low pressure cells with cyclonic patterns in the North Sea redirecting the jet stream coming across the Atlantic from the west. The "Mistral Winds" along with the "Tramontane Winds", also coming from the North at a similar time of year, both primarily bring dry conditions because of the dry continental air masses moved. Since much of the air flowing south is following the contour of the mountains and staying low it can often be considered stable.

This picture show the patterns of "Mistral
Winds."The High Pressure Cell is
anti-cyclonic as opposed to the cylonic
Low Pressure Cell. Both working together
to push the winds southeast.
This photo shows the air following the contour of the Mountains as
it crosses over southern France. This is the Tramontane winds coming
from the north and moving south.  They are carrying more moisture
further south than normal.



Since air always moves from high pressure to low pressure there is another interesting phenomenon that leads to the climate at the Calenques.  This is the diurnal flow. 
In the daytime breezes flow inland and at night
breezes flow out to sea.
This park is right next to the sea and at the base of the mountains causing heavy changes in pressure and temperature throughout the day.  The land heats faster and cools faster than the sea so this creates a daily pattern of changes in direction of breezes. With this change in heat the air will flow from the colder sea to warmer land in the day rising when it heats and falling as it cools and vice versa at night.  The motion of air coming off the Mediterranean is what gives Provence more accumulated annual rainfall per year than many inland regions of France.
Water heats slower and retains its heat longer because
 it is translucent and constantly mixing colder water
 with warmer water while land is opaque and has no
mixing as show in this picture.
References:
Allen, Casey. Class Lecture. Introduction to Physical Geography. University of Colorado Denver, Denver, CO. Aug.- Dec. 2012.
Fett, Bob. World Wind Regimes-Mediterranian Mistral Tutorial. NRL Monterey, Marine Meteorology Division. Dec. 2002. http://www.nrlmry.navy.mil/sat_training/world_wind_regimes/mistral/index.html
Images:
Wikipedia
Allen, Casey. Class Lecture. Introduction to Physical Geography. University of Colorado Denver, Denver, CO. Aug.- Dec. 2012.

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