Dirty snow (snirt) & melting point

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Discussion Overview

The discussion revolves around the phenomenon of dirty snow, often referred to as "snirt," and its melting behavior, particularly why it tends to persist longer into the spring compared to cleaner snow. Participants explore various factors that may contribute to this delayed melting, including environmental conditions and physical properties of the snow.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that dirty snow accumulates on roads and remains unmelted due to its mixture with dirt and exhaust fumes, questioning why it doesn't melt despite being darker and presumably better at absorbing light.
  • Another participant suggests that the dirty snow left in May may simply be remnants of the highest and most shaded snow banks, implying that location and exposure may affect melting rates.
  • A different viewpoint highlights that snow not exposed to sunlight absorbs heat through convection, which is a slower process, potentially explaining why some snow, like that on a deck, does not melt quickly.
  • Another participant discusses the impact of snow plowing, suggesting that packed snow becomes denser and takes longer to melt, and mentions the influence of thawing and freezing cycles on the melting process of curbside snow.

Areas of Agreement / Disagreement

Participants express differing views on the reasons for the delayed melting of dirty snow, with no consensus reached on the primary factors influencing this phenomenon.

Contextual Notes

Some assumptions about the conditions affecting snow melting, such as sunlight exposure and the density of packed snow, remain unresolved. The discussion does not clarify the specific contributions of each factor to the melting process.

Mephisto
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You know that dirty disgusting snow that accumulates on sides of roads over the winter, and then doesn't melt until well into May or something? Why is it that this snow refuses to melt? It mixes with dirt and exhaust fumes from the cars, and somehow becomes really hard and un-meltable.

Does anyone have an explanation? Its much darker, so it should absorb light much more easily and melt even faster! Its a puzzle :(
 
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I thought the dirty snow left in May was simply what was left of the highest and most shaded snow banks of the previous winter. I have no reason to assume a different melting rate for the late snow I see in my area.
 
If it's not in the sun, it absorbs heat via convection, which is a pretty slow process. I have some fresh looking snow on my deck that never seems to melt.
 
I think due to snow plows pushing the snow to the burm, many times, you have a layered effect and snow is "packed" thus denser relative to soft fallen snow around the packed snow..all things are relative and it takes mucho time to melt a packed snow mass..
also there may be severla thawing freezing cycles for the curb side snow pack and will make melting more difficult
 

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