Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Temperature and Evaporation
Name: Chuck M.
Status: educator
Age:  50s
Location: N/A
Country: N/A
Date: Tuesday, April 30, 2002


Question:
I always thought that higher temperatures cause more evaporation. Is it possible then that more evaporation takes place on the Great Lakes in fall and early winter when the difference between the water and air temperatures are maximum than in the heat of summer when the air temperature is in the 70s and 80s? I have heard it said that this is true, but it seems to fly in the face of physics to me, even though winds tend to be higher during the fall and winter seasons.


Replies:
Evaporation rate does depend upon temperature (the absolute temperature in kelvins) and typically this will range from 260 to 313 kelvins -- the log(vapor pressure) is proportional to 1/T. so while temperature is a factor these functional dependences tend to "squash" the temperature effect. Even more dominant are: 1. Relative humidity, which is lowest in the late fall and winter, and 2. wind speed, which is higher around Lake Michigan in the winter FOR SURE!

Vince Calder


Chuck,

Sunlight penetrates the water to heat it up very slightly and air temperatures can warm the water also, but these play smaller roles in evaporation of water than the amount of water vapor in the air above the water.

Evaporation from a water body with no internal heating (like a hot spring) is controlled by the water vapor content of the air above the water and by the amount of turbulence in the air that can take evaporated water vapor away from the water surface.

The less water vapor in the air, the more water can be evaporated from the lake, no matter what the temperature.

The more turbulence (usually increases with wind speed), the faster the evaporated water vapor is removed from the near the water surface, thereby increasing the rate of evaporation.

David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory


Click here to return to the Weather Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory