thermal dynamics of a farm pond: a progress report
TRANSCRIPT
THERMAL DYNAMICS OF A FARM POND: A PROGRESS REPORT
James D. BrownridgeBinghamton University
Department of Physics, Applied Physics and AstronomyBinghamton, New York 13902-600
Acknowledgment
Motivation
To better understand the behavior of water when it cools through ~4 degrees C
(~39.2 degrees F) its maximum density.
This is a report of what I observed when I tookmy experiments from the laboratory to the real
world environment.
Experimental set-up
Data collection
Data interoperation
Solar cell
1000 feet to a PASCO Xplorer GLX
(and ~350 ft. long)
Air + sun temp. sensor
Pond and Data Logging
Air temp. sensor
What we see on a sunny day
Surface
Pond Water Temperature
Sunrise
Bottom Mud
Surface water
126 128 130 132 134 136 138 140 142 144 146
0
5
10
15
20
25
30
35Unobstructed sun light
Sunset
Responses of the sensors to short term environmental changesA
rbitr
ary
units
Hours
Water
Solarcell
Air + Sun
True Air
Sunrise
Dark cloudSensors
1 2 3 4 5 6 7 8 9 10 11
Putting all the sensor data together
(Arbitrary units)
“In the spring the surface water warms up and the ice melts. A shallow convective
overturn resumes until the lake is oncemore isothermal at 4° C. Continued
warming of the surface produces a stablewater column.”
Encyclopedia Britannica
From the Literature
What have I learnedso far?
Things are Quite Dynamic in This Pond!
The Collapse of Stratification
No wind
13 April 2008 – 1 May 2008
Stratification buildup and collapse
The Collapse of StratificationCaused by cold front with light rain
Effect of Clouds Coming Between the Sun and Pond
Close-up View of Water Temperature Curves
(All in < 1hr.)
Spring vs. Fall
Spring (May 21-22) Fall (Oct. 7-8)
* *
Sun light interrupted by clouds is the major driving force throughout the water column.
Conclusion # 1
Day Night
Clouds passing between the sun and the pond causes major temperature swings
Sunset
Conclusion #1a
Sunrise
Conclusion #2
.
Intra day spread in temperature may approach 5°C
Thermal activity after dark ??
NO thermal activity after dark
Air Temperature is the Driving Force at Night
Conclusion #3
Thank you
? ? ?
Laboratory finding
Coldfront
As the water cools through ~4°Ca cold front move up the bottle
Below ~4°C
Above ~4°C
