Dew points on the rise this time of year

The 'comfort' factor for the past week or so hasn't been all that great due to high dew point temperatures.  A lot of this has been driven by the type of air mass that has been in place - very tropical and warm.  But, the increase in dew point temperature can also be attributed to what's around us.  And that's corn.  Believe it or not maturing corn can, and does, have a role in our weather.

It's a process known as 'evapotranspiration'.  And it's a combination of evaporation and transpiration.  We all know what evaporation means - the process by which water changes from a liquid to a gas or vapor.  But, we might not know what transpiration means.  Transpiration is when moisture escapes through the plant's leaves and enters the atmosphere.  Think of a plant stem as a giant wick that soaks up moisture from the soil with its roots.  As it does, some of that moisture is then released back into the atmosphere.  As the corn crop matures, or tassels, the area of the plant leave grows allowing more moisture to escape into the atmosphere.  That added moisture to the atmosphere can cause dew point temperatures to rise.  Something we typically see this time of year, especially in areas heavily surrounded by corn crops.  Once the crop has reached its peak, the evapotranspiration rate isn't as high.

A fun experiment to try would be to cover a plant with a plastic bag.  Within and hour or two, you will notice moisture on the inside of the bag.  That's transpiration.

These next couple of days, dew points will be touching close to 70 degrees, or higher.  That doesn't feel too comfortable when you step outside.  While most of it will be driven by the air mass that's in place, the higher dew point readings are also caused by evapotranspiration.

Many research projects have been conducted to try and understand this process, and to really gain an understanding of why this happens and how much of an impact it may actually have in the corn belt area.  Here is an actual research paper/project from an old colleague of my from school.   Differing types of vegetation along with soil characteristics could have an impact on evapotranspiration.