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Snow protocols
- Overview
- GLOBE Canada affiliate scientist
- Purpose
- Methods
- Equipment & resources
- Snow studies field sheet
- Data forms
- Links
Overview
Snow cover is important to global systems because it influences climate, hydrology, ecological processes, and human activities. Snow cover changes the energy transfer between the ground and atmosphere. Snow cover also is the frozen storage of water that affects soil moisture, runoff and stream flow. As an insulating layer snow provides cold weather habitat for a diversity of life. Humans shovel snow, use it, try to move in it and play in it.
In northern climates, snow generally begins to fall and accumulate during the late fall and early winter and melt during the late winter and spring. There is considerable variation in the amount of snow that falls, accumulates, the periods of accumulation and ablation (melting), the amount of water equivalence in the snow and the amount of snow that sublimes (evaporates directly from the crystal form into vapour). The layer of accumulated snow behaves in a number of ways which affects climate. Snow reflects more sunlight than soils and snow acts as an insulator which keeps the soil from cooling. Snow acts as a water source that is released in the spring.
Studies of the snow pack provide information about snow's insulating qualities, the water that is stored in the snow pack, the changes that occur within the snow pack over a period of time, how the snow pack provides a special habitat of a variety of plants and animals, and the stability (how likely it is to avalanche) of the snow pack.
GLOBE Canada affiliate scientist
Dr. Tracy Hillis
Dr. Tracy Hillis is a wildlife biologist with the Government of the Northwest Territories. It was during her research in Arctic zoology while conducting her master's degree research that she began her love of researching snow. From a biologist's perspective, trying to understand how the environment affects an animal is important in the overall understanding of the animal. Ms. Hillis likes to work in the winter because it's the season of testing for wildlife -- it's the hardest time of the year yet animals survive and thrive.
Dr. Hillis credits the development of her interest in snow and passion for winter studies to her mentor, Dr. Gerard Courtin. For thirteen years, Tracy researched the effects of snow on small mammals, voles and mice, foxes, bears, wolves, moose and caribou. After completing her Ph.D. thesis on woodland caribou and disturbance, she was hired as the Northwest Territories' first climate change biologist. Studying snow is a useful indicator of climate changes.
Dr. Hillis has developed and implements the Northwest Territories first snow research in the boreal forest. She is responsible for the assessment of climate change on wildlife and research as well as being the biologist for the development of snow programs in NWT. Dr. Hillis is keen to have students involved in snow studies and gathering data from different regions.
Purpose
The field observations are designed to provide information that relates to climatology, hydrology and our use of snow. These observations examine properties such as date of snowfall, snow accumulation and depth, layers of snow, temperature changes in the snow profile, crystal size and shape for different layers, density and water equivalent of the snow pack, and hardness of layers.
Methods
Recording depth of accumulated snow and new snow
Accumulated snow:
A single measure of the depth of snow may not be accurate because snow may move when it falls. Some areas will be blown clear while others will be piled into drifts of snow. To account for such differences, it is necessary to average a number of depth measurements. Snow Measurement Poles are made of 2 cm × 2 cm × 1 metre (or longer) sticks or PVC pipes with an attached measuring tape showing centimetres of depth. You will need to vary the length of the snow poles used depending upon maximum snow falls in your area. Five Snow Measurement Poles are placed at five metre intervals along a transect in an open, level area that will not be disturbed during the winter. Snow Measurement Poles are pinned on a flat clear ground surface before any snow falls. Snow depth measurements are made at each Pole at regular times (i.e. once a week) and after each new snow fall. Record snow depth to the nearest cm. Take these measurements without disturbing the snow around the Snow Measurement Pole. Set a track used to observe snow depths at least three metres from the snow poles.
New snow depth:
One additional Snow Measurement Pole should located in an area free from drifting snow. This pole is used to measure depth of new snowfalls. After each snowfall, a piece of heavy white paper with a hole in the middle is slid over the snow pole covering the new snow. With the next snowfall, the depth of new snow is then recorded as the depth of snow on top of the paper. Each successive snowfall requires a new piece of paper. record snow depth to the nearest cm. Try not to disturb the snow near this Snow Measurement Pole.
More detailed snow studies
The following protocols provide a number of more detailed studies of snow. They include observations and measurements of snow pack, identification and measurement of layers in the snow pack, temperature variations, calculations of the water equivalence of the snow pack, identification of the snow crystal type and size in different layers in the snow pack, and the hardness of layers in the snow pack.
Snow pack studies
A snow study site -- the snow pit:
A pit is dug in the snow to conduct these studies. It should have a smooth face that points away from direct sunlight. The pit should be large enough for two or three people to work in it. Locate snow pits in areas that have not been disturbed since the first snowfall and will not disturb other snow studies. All observations and measurements will be made along the smooth wall surface.
Snow layers:
Layers of different textures and types of snow form and change in the snow pack. Begin by gently pushing a plastic card (Snow Card) vertically through the snow pack. You may be able to feel the layers more easily than you can see them. Identify the boundaries between each layer. Make a series of steps of each layer along the smooth face of the snow pit. Measure and record the thickness of each layer starting at the ground level. Draw a line across the data sheet at the corresponding height of the boundary layers. Count and record the number of layers.
Snow temperature variation:
Snow insulates the ground and moderates the temperature changes between the air and the ground. Temperature measurements should be taken as soon as the snow pit has been dug. The thermometer should be carefully inserted to its full extent into the snow. Be careful, thermometers will break very easily! Sufficient time should be allowed for the thermometer to equilibrate (approx. 3 minutes). Temperatures are taken at five regular intervals between the ground and the snow surface. Also record the air temperature in the shade. Record and plot these snow temperatures on the data chart.
Snow water equivalence:
Layer measurement method: Water is stored in the form of snow. The amount of H2O in the snow pack may change over time. Snow may be released to the atmosphere through sublimation. Snow may also melt and run off or be absorbed by the ground. The amount of water stored as snow is an important measure. Measuring the density of the snow pack either layer by layer or across the entire snow pack, provides an equivalent to the amount of water stored in the snow pack. For example: The weight of 100 mL of snow is compared to the weight of 100 mL of water which is equal to 100 g. This provides a water equivalent. Measurements using the 100 mL plastic container are made by pushing the container into the layer. After the container has been pressed into the layer, use a flat surface to cover the open surface while it is still in the snow layer. Remove the container and trim the ends so that the core is flush. Weigh the 100 mL snow core and container with the spring scale. Subtract the container weight from this to find the weight of the snow core in grams. Calculate snow density by dividing the weight of the snow core (g) by 100 mL (the core volume).
Making a 100 mL plastic container for snow layer sampling
Make a 100 mL plastic container. Cutting the top off a recycled pill bottles works well. Wash, pour 100 mL of water into the pill bottle, and mark the level, then cut the bottle to this size. Drill a 5 mm hole in the bottom. This allows the air to escape when taking the snow core sample. Another hole in the side near the top is used for weighing the container on the spring scale.
Remember: 1 cc H2O = 1 mL of H2O = 1 gram of H2O
Example: 100 mL of H2O weighs 100 g
Calculating snow density and water equivalent for each snow layer:
Weight of container (A): _________ g
Weight of snow core & container (B): _________ g
Weight of snow core (W) = B - A: _________ g
Volume of snow (V) = volume of container: 100 mL
Density of snow = weight ÷ volume or W/V: _________ g/mL
Expressed as a decimal, this represents the water equivalent _________
Single measurement method: Another method is to use a stove pipe section to capture a cross section of the snow pack. Insert the stove pipe into the snow pack. Push a clip board under the stove pipe while it is in the snow pack. Keeping the snow captured, dump the contents into a plastic bag (i.e. garbage bag). Record the depth of the snow pack at the sample point. Calculate the volume of snow in the stove pipe. Weigh the garbage bag with snow and then subtract the weight of the bag to get the weight of the snow column. Calculate snow density by dividing the snow weight by the volume of the stovepipe sample (surface area × depth of snow). This provides a water equivalent because water density is 1 gm per mL.
Calculating snow density for the entire snow pack with a single cross section sample
- First calculate the volume of the snow sample.
Measure the diameter of the pipe (D): _________ cm
Calculate the radius of the pipe (r): _________ cm
Area of pipe (A) = πr² = 3.14 × (radius of pipe)² = _________ cm²
Volume of sample (V) = area (A) × depth of snow: _________ cm³
- Next determine the weight and density of the snow as explained in the box above with the snow layer sampling and continue calculations to determine the water equivalent.
Average snow crystal size:
The size and types of snow crystals influence the amount of water in the snow pack and the stability of the snow pack. Observations of snow crystal size and shape should be made for each snow layer. Crystal size is determined by placing crystals on the 1 mm and 2 mm grids. These grids provide a reference to determine the size of the average crystals. At least 20 crystals should be examined and an estimate made of their average size. Use the loup when examining the crystals on the grids. You should be able to estimates crystal size to the nearest 0.5 mm. When the crystals are bonded together they must be broken apart before the measurements can be made. In the case of extreme bonding (e.g. ice layer) or in very wet snow, crystal size and shape lose their meaning and need not be recorded. Record the size of the crystals in each layer.
Types of snow crystals:
Snow crystals are initially formed in the atmosphere. After falling, crystals change through processes of sublimation, melting and refreezing. The type of crystal found in the snow pack determines the stability of the snow, water content, depth of the snow pack and density of the snow layers. Identifying the types of crystals in each layer helps in understanding the characteristics of the layer and snow pack. The following types of crystals may be identified.
Type 'a' crystals: Type 'a' refers to new snow composed mainly of whole crystals or parts of broken ones. Snow such as ice pellets and hail do not belong in this class. Type 'a' snow is usually very soft. These crystals are classified on the data sheets as:
- New snow (symbol +) is represented by the classic six-sided crystal and by plates of hexagonal crystals. There are more than 100 classified types of new snow crystals.
- New snow, rimed (symbol r) is new snow that is made of droplets that freeze onto a snow crystal called rime. New snow rimed are crystals that have additional deposits of ice on the outer surfaces of the crystals.
- Graupel (symbol X) When a snowflake turns into just a ball of rime, which is called graupel.
Type 'b' crystals: Type 'b' snow refers to snow during the initial stage of settling. It is composed mainly of fragments of crystals but has not yet reached the stage of very fine fragments that is the end of the process of settling. Although is has lost a great deal of its crystaline character, some crystalline features can be observed; it still sparkles. Type 'b' snow is usually fairly soft. These crystals are classified on the data sheets as:
- Partially settled (symbol Λ) These are fine fragments of snow that have not yet changed through metamorphism.
Type 'c' crystals: When snow is transformed by melting or melting followed by freezing, it completely losses all crystalline features and its grains become irregular and more or less rounded. This is type 'c' snow. It has no sparkle effect even in bright sunlight and can be readily recognized by its dull appearance. It is usually fairly soft when wet, but can be very hard when frozen. Type 'c' snow grains may be any size from very fine to very coarse. These crystals are classified on the data sheets as:
- Rounded grains (symbol
) - Melt-freeze particles (symbol O)
Type 'd' crystals: At temperatures well below freezing and without any apparent melting, snow is transformed into Type 'd' by deposition of water vapour removed from crystals deeper in the profile by the process of sublimation. Deposition of this vapour higher in the profile produces irregular grains with flat facets. These layered facets are visible with a lens and give the snow a distinct sparkle effect in the bright sunlight. Type 'd' snow is usually fairly hard. These crystals are classified on the data sheets as:
- Faceted crystals (symbol
)
Hoar: Hoar is characterized by its hollow cup-shaped crystals. These crystals are produced by a very low rate of deposition of sublimed vapour during a long uninterrupted cold period. Depth hoar is most frequently found directly below a more or less impermeable crust in the lower part of the snow cover. The strength of a layer of depth hoar is very low and the structure of the layer falls at the slightest touch. These crystals are classified on the data sheets as:
- Surface hoar (symbol
) - Depth hoar (symbol
)
Snow hardness:
The stability of a snow pack may be influenced by the hardness of a layer in the snow pack. A soft layer of snow under a number of harder layers may make the entire layer unstable. Snow hardness readings should be taken in the centre of each snow layer including ice layers. We estimate hardness of the layer using the Hand Test technique. The Hand Test method uses a 100 gram pressure (a gentle pressure) against the face of the layer. If the fist, four fingers etc. go into the layer, then the layer is categorized as that type of hardness. If the layer is very soft, then it is quite unstable. Use the following scale to determine the hardness of the snow in g/cm². Record the type of hardness on the data table.
| Class | Pressure | Symbol |
| Fist | 10 g/cm² | F |
| Four fingers | 25 g/cm² | 4F |
| One finger | 100 g/cm² | 1F |
| Pencil | 500 g/cm² | P |
| Sharp Point | 1000 g/cm² | K |
Additional snow study activities
Photographing snow crystals:
For good pictures you need some good subjects, and not all crystals are ideal for snow crystal photography. The first step is to use a small magnifying glass to look at the crystals the next time it snows to see if there's anything worth photographing. Not every snow fall produces great crystals. You will need to make your camera into a macro camera. Snow crystal photography is somewhat beyond what's normally called macro photography, but at the same time it's not as demanding (or expensive) as full-blown photomicroscopy. Take a 10x to 12x loup and fix it to an adaptor made to screw into the front of the camera. You can do this with digital cameras that have a manual focus. Selecting the best crystals requires care. A hands-off technique is to simply catch crystals on a cold glass plate and photograph them in place, but this is not always practical. In particular, one usually wants to select the best specimens, and then transport them to a photographic stage. Utensils for this task include small sticks, feathers, etc., and of course a steady hand is useful. Sublimation will rapidly cause the sharp crystal facets to become rounded. Although rounded edges do produce a pleasing prism-like effect, it is usually desirable to minimize the effects of sublimation by photographing crystals as they are selected. Snow crystal photographs should be taken quickly. Other techniques include catching snow crystals in a shallow beaker of cold hexane, which largely eliminates the sublimation problem.
Equipment & resources
For snow depth measurements
Snow Measurement Poles:
- Number of Snow Measurement Poles needed: 6 (5 + 1)
- Dimensions: 2 cm × 2 cm × 1 m or higher (depending on snow depth in your area)
- Construction material: wood or PVC
- Construction details: secure either a nail or a wood platform on the bottom of the stake to rest it on or secure it into the ground; using clear packing tape, tape a measuring tape into place on the Pole (place 0 cm at the bottom of the stake)
For snow profiles
Snow pit study equipment:
- Snow measurement chart
- Snow card
- Thermometer (consider attaching something colourful to the thermometer so that it is easily found if misplaced)
- Measuring tape
- 100 g spring scale (for 100 mL snow samples)
- 2-5 kg spring scale (with 20 g or 50 g graduations respectively) -- for stove pipe samples
- 100 mL cylinder to measure snow density
- Cylinder to measure snow density for entire profile -- i.e. metal stove pipe or heating duct pipe
- Garbage bag for measuring weight of snow sample
- Jeweller's loup, 5x or 10x magnification
- Bag to hold small pieces of equipment (anything white will likely be lost in snow, best to use a coloured bag)
Snow studies field sheet
Data forms
- Snow depth data sheet
- Snow pit data (for the classroom record)
- Sample snow recording sheet (for the field)
A convenient way to take the field sheets into the field is to use "magic carpet" plastic cut to fit the field sheet. The plastic offers a firm backing for writing on when recording field observations, it's waterproof, and a convenient size. The field sheet can be attached to the stiff plastic backing by cerlox or gluing a big clip in place.
Links
