36
Ice grows in many forms. As mentioned in the other answer, all of the ice we are going to observe is Ice Ih, but there are many other forms. See this phase diagram of water:
Image courtesy of Cmglee on wikipedia
The different ice regimes grow different crystalline shapes. Ice Ih grows hexagonal crystals and in certain regimes you can find triangular and ...
26
H2O ice on Earth crystallizes with a structure called "Ice-Ih" which is hexagonal. The structure is dependent on the dipole properties of H2O-molecules. Similar to what water does with ions to bring them into solution, the crystal structure is dependent on the energetically favourable alignment of the dipoles. In Ice-Ih the most favourable alignment is a (...
18
To add to both Spießbürger's and casey's excellent answers, hydrogen bonds are the reason why some snowflakes are six-sided. His was alluded to, but I think it could use a bit more extrapolation.
www.physicsofmatter.com
The image above shows an oxygen atom bonding with two hydrogen atoms (water). We can call these covalent bonds for our purposes, although ...
17
What's the minimum "uprightness" for it to not get obscured by snow and stay readable throughout the year?
The answer to this problem is not in the angle at all. No amount of math will give you an angle at which you can reasonably presume your surface will remain clear. Snow can (and does) accumulate on vertical and even negatively sloped surfaces. Instead ...
15
Normal ice (as in refrigerated ice cubes) mostly has uniform crystalline structure - water molecules are in a perfect hexagonal grid, which enables it to be transparent.
Not all ice is like that - for example, if you freeze water that contains tiny water bubbles due to a faucet aerator, the resulting ice would likely look white because the tiny air bubbles ...
15
Snow has a very high albedo. Actually, it reflects all wavelengths of the visible spectrum, whilst absorbing no particular wavelength. Hence the eye averages out the multiple reflected wavelengths as 'white' - as is the case with most fine granular solids.
14
A blizzard is defined as
sustained wind or frequent gusts >= 16 m per second (30 kt or 35 mi per hour)
falling / blowing snow, frequently reducing visibility to less than 400 m (0.25 mi)
3 hours or longer in duration
A storm meeting these qualifications is a blizzard. Note that snowfall is not necessary, a sustained 35 kt wind blowing snow for 3 hours ...
13
An object on an angular surface will fall off, when forces exerted along the slope (gravitational, tangent to the surface: gt) are greater then those pressing the object to the slope (gravitational, perpendicular to the slope, gp) or working in the opposite direction on the slope (friction, $fr$).
As an example, $10\ \mathrm{cm}$ of snow, on a 0.5-by-1-...
11
The clouds in which snow originates must of course be below the freezing point 0°C = 32°F.
Two factors allow snow to reach the surface when the near-ground air temperature is above freezing.
The time delay --- snowflakes may not have time to melt before reaching the surface if the surface temperature is not much above freezing. Strong downdraft air motion ...
11
This is a large glacier calving event. Calving occur at the front of the glacier, probably a very wet (and likely warm based) glacier where a considerable amount of water is flowing out of the system (thus from the glacier to the sea). The amount of water is important as it can accelerate the ice flow speed on the valley floor, enabling the breaking of big ...
10
The snow density, which is the "conversion function" you are looking for, of fresh fallen snow varies with atmospheric conditions, vapour saturation and temperature since these parameters determine the snow grain morphology (See this figure from SnowCrystals.com; I leave it as a link for copyright reasons). Densities can vary from as low as < 100 kg m-3 ...
10
Email response from Alex Jacques (Programming Support - MesoWest):
The exact interpretation can vary between data providers to MesoWest,
but in general it refers to the amount of snow that has fallen on an
"interval board". In several cases, stations have boards where
snowfall is recorded, and then the board is wiped clean at set
intervals (...
9
Snow fall can occur under several conditions. In this I am assuming conditions typical for mid to high latitudes. Association with cold-warm fronts are probably most common. Snow fall in mountainous areas can be associated with orogenic clouds and precipitation, when air is raised due to topography creating conditions for precipitation. In addition it is ...
9
It is likely snowing somewhere in these clouds and graupel exist transiently on their way to becoming hail, but its not likely that you will see either at the surface.
You can make a first order approximation of a pyrocumulus cloud by putting a very strong heat source at the surface in an environment otherwise favorable for severe convection. What you'll ...
8
@Peter Jansson provides a much more thorough answer, but for a quick conversion of expected liquid water equivalent to expected snow depth:
1 inch liquid water = 10 inches snow for warm storms
1 inch liquid water = 20 inches snow for cold storms
or
25 mm = 25 cm for warm storms
25 mm = 50 cm for cold storms
Often a certain climatology will trend one ...
7
As mentioned in the comments, the air temperature is the deciding factor. In the Troposphere, until ca. 15 km, the temperature decreases by about 6 °C per km altitude (more info on the lapse rate here).
As an additional factor, the air temperature on ground levels is generally higher in urban environments, like Paris. Therefore, the natural outer ...
6
I'm assuming this question is asking about the sea ice in the Arctic Ocean as opposed to ice caps such as that over Greenland. The sea ice on the Arctic Ocean is predominantly (overwhelmingly!) frozen ocean water.
The Arctic Ocean loses 17 to 18 thousand cubic kilometers of ice every summer, only to regain most of that melted ice during the long Arctic ...
5
Farrenthorpe is right, a little surfing the net for snow distribution would clarify the picture for you. However, I think you are referring to certain times when it rains further north and snows further south. There are several reasons for local anomalies, of which the most important is the dynamics of the polar jet streams. These are strong high-altitude ...
5
The albedo of the snow would be the primary reason the snow is not melting. Using a simplified model there are two main sources of heat energy that the snow can absorb, the heat from the ground below, and the heat from the sun and atmosphere above. The ground and the atmosphere are going to be colder at high elevation because of the lapse rate that gansub ...
4
The Intergovernmental Panel on Climate Change summarizes the state of scientific understanding of climate change every few years and at least as far back as 2002 has projected a range of changes in extreme weather.
In the IPCC report for 2002, the Working Group II: Impacts, Adaptation and Vulnerability summarized the existing scientific understanding in may ...
4
A measureable amount of precipitation is considered to be at least 0.01 inch of water. Since on the average 10 inches of snow melt to 1 inch of water, this corresponds on the average to 0.1 inch of snow. Anything less is considered a trace (too little to measure).
3
Gordon has an excellent answer to one version of your Q. In case you are asking a more basic Q, here is a try at an answer.
Vini, think about the monsoons. Cooling the soggy parcel of air causes rain, but continued gradual cooling as it crosses an area of land does not necessarily create even heavier rain (leaving aside the rapid cooling that happens when ...
3
I don't know if someone has conducted statistical research on this. It certainly depends on the situation. Here are some situations:
More snow in coast
Like @gerrit commented, elevation increases precipitation as air is forced to lift up and thus cools condensing water vapor -> rain/snow. This is true when predominant winds are from the sea.
Lake-effect ...
3
Addressing your hypotheses in order, I'll start with (1) cloud cover. Here you can differentiate firstly between day and night time. While during the day, clouds will reduce heating of the ground by means of reflection of incoming solar radiation, during night, the clouds are the main contributor to thermal back radiation towards the surface and absorption ...
3
Full disclosure: Being in Florida, I don't spend as much time watching winter weather, and don't have great experience correlating radar precipitation totals to actual snowfall. Is it spring yet?
But I do at least some background and information, and so hopefully can add some insight.
Using radar is certain to have imperfections...
Smaller Radar Caveats:
...
3
You could fill the gaps with the analysis products of numerical weather prediction. NCAR for example (RDA UCAR) hosts the NCEP North American Regional Reanalysis (NARR) with data from 1979 to 2018 including snow cover (NARR) in 3-hourly intervals.
But I would guess it depends on your goal:
You can make an educated guess (bayesian approach, combining ...
3
According to Caltech physics professor Kenneth G. Libbrecht's site SnowCrystals.com
This monster is, to my knowledge, the largest snow crystal ever photographed. It measures 10.1 mm (0.4 inches) from tip to tip (averaged over the three axes). ... Note that this is a snow crystal: a single crystal of ice ... Larger snowflakes have been reported, but those ...
3
The latitude and longitude of each pixel is not stored in the HDF file. But using
metadata=hdfinfo('file_name.hdf');
You can get the info to generate those latitudes and longitudes. In metadata.Attibutes you will find this among other things:
GridName="MOD_CMG_Snow_5km"
XDim=7200
YDim=3600
UpperLeftPointMtrs=(-180000000.000000,90000000....
2
The question asked is "why do snowflakes form into hexagonal structures".
I see snowflakes as following the framework of a flattened cuboctahedron.
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