Tears of Wine

Wine, a mixture of water and ethanol (a type of alcohol), exhibits a phenomenon that could be a part of the process to extract water vapor from air.


What is Air?
Air, is the name we have given to the atmosphere that is closest to the ground that contains a mixture (not chemical compound) of gases and water (in vapor, liquid and ice crystal form) that sustain and promote life, as we know it, on planet Earth.

Drops & Rivulets in a glass of wine
Source- www.monashscientific.com

Tears of Wine
Mixtures, that are physical and not chemical in nature, contain interfaces between the mixed materials. An example can be found by looking up in the air (an exaggerated one, I admit) - an interface exists between a cloud and the air around it. 
When an interface exists between materials that have very different surface tension forces, mass transfer occurs along their interface. 
The amount of mass transfer is impacted by a number of factors that include, amongst others,  the differing surface tension forces, temperature, pressure and evaporation rates.
This effect can be clearly seen in a glass of wine, in the formation of drops and rivulets on the insides of the glass surface above the wine surface.

Drops and rivulets in a wine glass
Source - newzstuff.blogspot.com

These drops and rivulets are the result of the different surface tensions of water and ethanol that constitute wine, and the fact that ethanol evaporates much faster than water does.
The scientific name for this phenomenon is: The Marangoni Effect.
In wine, as water and alcohol are not mixed completely homogeneously, different regions exist with different concentrations of water and of alcohol. 
In regions, where concentration of alcohol is greater, this alcohol pulls on the regions around it (where water concentration is greater) because the surface tension of alcohol is greater than the surface tension of water. The primary result is a movement of water away from alcohol and an increase in the separation between alcohol and water.

Moving a glass or
holding it at an angle
Source - 123rf.com

While this phenomenon was discovered and explained in the 1850s and 1860s, wine drinkers just know that they need to continuously move the wine glass in a circular pattern of motion to make the wine taste consistent and the one they had when the wine was pored from a freshly uncorked bottle.
This circular motion is really only focused on creating a more homogeneous mixture of alcohol and water. 
This motion does encourage increase in alcohol evaporation, and increased aeration (detrimental to taste and aroma?) but, hopefully, the wine is consumed before too much alcohol evaporates or too much air gets added to the mixture of water and alcohol.
Surface Tension Values Between Water and Air

Surface Tension
Interface	Temperature	milliNewtons per meter γ in (mN·m–1)
Water - air	20 °C	72.86±0.05[1]
Water - air	21.5 °C	72.75
Water - air	25 °C	71.99±0.05[1]