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19 March, 2002


Sunny, High 32, Low –7

The Science Behind Thermal Conductivity (keff),


Snow density (p) is a measurement we use to calculate

thermal conductivity, which is one of two functions of

conductive heat flow. The other function is

temperature gradient.

Expressed in W/m/K (Watts per meter per Kelvin),

thermal conductivity is the ability to insulate and

conduct through an area. There are two equations used

depending on the mean snow density.

If the mean snow density is higher than .156

, then we use this equation.

(0.138 – 1.01p + 3.233p2)

If the mean snow density is equal or lower than

.156 g/cm3
, then this equation is used.

(.023 + .234p)

Let’s Practice

Recall mean snow density you calculated on March 10th,

(.1649073 g/cm3). This value is higher than .156

g/cm3, therefore we use the first equation.

A. keff = (0.138 – 1.01p + 3.233p2)

B. keff = (0.138 – 1.01 (.1649073) +


C. keff = (0.138 - 0.1665563 + 0.0879195)

D. keff = 0.0593632 W/m/K

If the mean snow density is .1388112 g/cm3, what would

be the thermal conductivity? See tomorrow’s journal to

check your answer.

Trees in Central Alaska

On our way to Poker Flat along Steese Highway, the

view of Fairbanks becomes veiled with black and white

spruce trees as well as aspen, birch, and poplar

trees. Due to permafrost, tree roots extend

horizontally immediately below the surface. The result

of shallow roots, trees are often found lopsided.


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Combination of black and white spruce trees.

Trees near Jalpertia pond

Image from the UAF museum

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