soil stats 1

[civeng800]

Does anyone know the temperature and relative humidity of soil, with respect to depth and season? Are there any databases on the internet where I can find such stats?

 

[Focht3]

Temperature might be found with the National Weather Service (for the U.S.) But forget relative humidity; it's related to soil moisture, mineralogy, soil suction, etc. - very site specific. You can measure soil relative humidity using a variety of techniques, but this is a pretty complicated subject area.

What are you trying to accomplish?



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[DBNodurf]

regarding "relative humidity," the correct term is degree of saturation; the definition of relative humidity is the ratio of the vapor pressure of moisture in the air at a given temperature to the vapor pressure of saturated air at that temperature; i.e., the vapor pressure of the air at some temperature, x, where x is >= the dew point of the ambient condition relative to the vapor pressure at the dew point. These concepts have no significance in normal soil mechanics; they would only be relevant in mechanics of unsaturated soils, but perhaps that is why you need them. If so, I have learned something new today, and that is a good thing!


D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...
Principal Engineer/Geologist
Atlantic Geoscience & Engineering
Charlotte, NC

 

[Focht3]

Hmmm,

I'll respectfully disagree. Rh (relative humidity) is different from S (degree of saturation.) They have different definitions and means for measurement.

Two soil samples with identical dry weights can be in identical jars with identical amounts of water in each jar. Both jars have identical values of S.

Assume that both jars are also at the same temperature. The Rh in one jar is lower than the other. Why? The jar with the lower Rh has salt in it. The difference between the Rh values has everything to do with the type and quantity of salt present.

Pore water chemistry is a crucial factor in evaluating Rh, and it is similar to - but different from - degree of saturation -

It's a fun (and challenging) topic...



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