1. Avalanche forecasting: Snow density in relation to precipitation
Lena B, Emma L, Jenna T

2. Introduction to snow density
Why look at snow density?
Avalanche science
Water content
Emma
Less detail
Define porosity = how porous something is,, how easily liquids can pass through
Avalanche science == the more dense snow is, the more likely it is to form a slab of snow → plus the added weight of precipitation such as rain causes these slabs further instability ⇒ they fall down potentially resulting in an avalanche
We are not focusing as much on water content as we are with avalanche science. However, snow density is helpful in determing water content in a designated area. This water content may help hydrologists/other curious people to understand how much water will be available in runoff → important to california’s water supply

3. Our Hypothesis
Research Question: Is snow density affected by change in weather? (ie. snow and rain)
Claim: The density of snow will be greater after heavy rainfall due to increased water content in the snow that causes compression, therefore increasing mass and density. Conversely, after a snowfall, the density of the snow will decrease.
Lena

4. Reasoning
Water compacts snow → added weight causes snow to slide down in clumps
Weak layers
Rain increases separation
Lena
While water compacts snow (you might think it would help make the snow less mobile) the sudden added weight cause the snow to slide down in massive clumps
Weak layers
If it snows -- you add to the week layer and then the rain just causes it to slip
Could or could not…
Why?
Runoff

5. Materials Methods 250 cc sampling cylinder 9 ziplock bags Scale Ruler
pH meter
Pick sites for data collection
Twist cylinder into upper layer of snow up to designated line
Shovel away snow from cylinder
Slide clipboard underneath cylinder
Place snow sample into bag
Measure mass of sample + bag
Subtract bag mass (~6 g)
Calculate snow density (g/cm^3)
Emma
Bottle prevents packing
Give barely enough info so a scientist could replicate

6. Our Sites
Forested Area
Meadow
Lena

7. Density (x100)/snow water percent
Sample
Mass (g)
Volume (cm^3)
Density (g/cm^3)
Density (x100)/snow water percent M1 28
0.113
11.346
M1.2 24
0.097
9.725
M1.3 23
0.093
9.320
F1.1 29
0.118
11.751
F1.2 22
0.089
8.914
F1.3 51
0.207
20.665
M2.1 42
0.170
17.018
M2.2 59
0.239
23.907
M2.3 82
0.332
33.226
F2.1 55
0.223
22.286
F2.2 60
0.243
24.312
F2.3 58
0.235
23.502
M3.1 61
0.247
24.717
M3.2 50
0.203
20.260
M3.3 54
0.219
21.881
F3.1 53
0.215
21.476
F3.2
F3.3
Data
Emma
On the left, mass goes up by 25, on the right water percentage goes up by 10
Delete graph → make table bigger
Box different days and explain weather -- label it

8. Emma

9. Statistical Evidence Comparing Day 1 to Day 2
Jenna
Show bar graph of difference (of means?)
Write caption below to show what the graph means n=

10. Statistical Evidence Comparing Day 1 to Day 3
Jenna

11. Statistical Evidence Comparing Day 2 to Day 3
Jenna

12. Potential Sources of Error
Measuring instrument lacks sophistication → inconsistent volume
Small sampling size
Scale doesn’t provide exact measurements
Lena

13. Findings
Our claim was supported by evidence acquired through data collection, statistical testing, and further online research
Data collection showed a higher density for snow collected after a rainfall than before
2 sample T interval proved that the true mean value of snow density pre-rain was less than the true mean value of snow density post-rain
P value < .05
Findings by Jim Frankenfield, director of CSAC Avalanche Center, show how our data has an effect on snow packs and avalanches
“If the precipitation comes in the form of graupel or rain it generally has an adverse effect on stability...Rain wreaks havoc when it percolates into the snowpack. Free water tends to make weak layers weaker. It can also flow along planes parallel to the ground, such as crusts, lubricating bed surfaces.”
Jenna

14. Implications of our findings
Our results correspond with avalanche danger levels
Density is not perfect BUT… it remains a decent indicator
(3/20) No precipitation → 2
(3/21) Rain → 3
(3/22) Snow → 4
Emma
DAY THREE == Avalanche → Rapid change in density
Calcuating snow desnity was a really cool experience but it also really cool seeing how it tied into actual avalanche science
Advisory on sierraavalanche → week in rview
Our results ultimately did fall in line with

15. Future Research Questions
How does the density of different layers of snow increase the likelihood of an avalanche?
How do weather changes (ie snow or rain) affect the density of lower layers of the snow pack?
How does temperature change have an affect on snow density?
How is density affected by tree coverage or lack thereof?
How does human presence affect the density of lower layers of snow and how might that have an effect on the occurrence of avalanches?
Lena
Just share ideas,, not always how

16. Thank you!

17. Websites
EMMAMAKMKAMK