thermal dynamics of a farm pond: a progress report

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